| AC |
Abbreviation for alternating current. |
| AC Blackout |
Total loss of distributed commercial ac feed power. |
| AC Brownout |
The condition that exists when the AC line voltage drops
below some specified value. |
| AC Input |
Electrical power in the form of alternating current
(AC) supplied to the UPS and bypass. |
| AC Input Impedance |
The impedance of the AC input at the input terminals
of the UPS with the UPS disconnected. |
| AC Line |
The set of conductors that route AC voltage from one
point to another. |
| AC Line Filter |
A circuit filter placed in the AC line to condition
or smooth out variations that are higher in frequency than the line
frequency. |
| Actuator Fuse |
A fuse incorporating some mechanical means to close
a dry (un- powered) contact when the fuse opens, such that an alarm
and/or control function may take place. |
| AH |
Abbreviation for ampere hour. |
| Air Gap |
A space in the magnetic core, void of magnetic material,
used to lower the permeability and increase the ampere turns before
the core saturates (provides the required reluctance to the flux path).
The gap is filled with a non-magnetic material other than air. |
| Alarm |
A method or signal of attracting attention to an abnormal
condition in the UPS. |
| Alarm Circuit |
A circuit with a primary function of alerting an operator
by either a visual and/ or audible signal that an abnormal condition
exists. |
| Alarm Interrupt |
Stop of normal UPS operation via activation of an alarm
condition having a control function. |
| Alive (Live) |
Electrically connected to a source of voltage or electrically
charged so as to have a voltage different from that of earth; the
term may be used in place of "current-carrying" where the
intent is clear, to avoid repetition of the longer term. |
| Alternate Source |
Secondary or backup AC feed to the static switch of
the UPS system which is also termed Bypass Source. Often it is unprotected
commercial power See Commercial AC Power. |
| Alternating Current (AC) |
A periodic current the average value of which over a
period is zero. Unless distinctly specified otherwise, the term refers
to a current that reverses at regularly recurring intervals of time
and which has alternately positive and negative values. |
| Ambient Temperature |
The temperature of the environment immediately surrounding
the UPS into which the heat of the UPS is dissipated. For forced air-cooled
units, the ambient temperature is measured at the air intake. Also
see Operating Temperature, Storage Temperature, Temperature and Coefficient. |
| American Wire Gauge (AWG) |
A standard for sizing cross-sectional areas of wire,
and for measuring sheet-metal thicknesses. |
| Ampacity |
Current carrying capacity of electric conductors or
devices expressed in amperes. |
| Ampere (A) |
Electron or current flow representing the flow of one
coulomb per second past a given point in a circuit. |
| Ampere-Hour (AH) |
A measurement of a quantity of electricity computed
as the product of current (in amperes) and time (in hours). |
| Ampere Hour Capacity |
The number of ampere-hours which a storage battery can
deliver under specified conditions such as temperature, rate of discharge
and final voltage. |
| Ampere Turns |
The S1 unit of electromagnetic force defined as the
field produced by the flow of one ampere in a single turn of wire
in a coil. |
| Amplifier |
A circuit or element that provides gain. |
| Amplifier, Comparator |
See Comparator. |
| Amplifier, DC |
A direct current amplifier that can provide gain for
zero-frequency signals. |
| Amplifier, Differential |
An amplifier which has available both an inverting and
a non-inverting input, and whose output signal is proportional to
the algebraic difference between the two. |
| Amplifier, Inverting |
An operational amplifier that produces an output signal
of nominally equal magnitude and opposite algebraic sign to the input.
Such an amplifier can be used with degenerative feedback for stabilization
purposes. |
| Amplifier, Noninverting |
An amplifier who's output is the same algebraic sign
as its input. |
| Amplifier, Operational |
A DC amplifier whose gain is sufficiently large so that
its characteristics and behavior are substantially determined by its
input and feedback elements. Operational amplifiers are widely used
for signal processing and computational work. |
| Anode |
The electrode at which an oxidation reaction occurs.
During discharge, the negative electrode of the cell is the anode.
During charge, the situation reverses and the positive electrode of
the cell is the anode. |
| Anode Terminal |
In semiconductor diodes, the terminal that is positive
with respect to the other terminal when the diode is biased in the
forward direction. The positive terminal, such as the plate in an
electron tube. |
| Apparent Power |
The product of the RMS current times the R/ms voltage. |
| Arc |
|
| Arc Quenching |
(Electronic see Surge Arrester). Mechanical An arc-extinguishing
medium to facilitate current interruption. |
| Arcing Time |
Infuses, the time measured from when fuse element melt
time ends to when current is interrupted and becomes zero. |
| Astable Multivibrator |
A free-running oscillator circuit using resistors and
capacitors for feedback coupling. It has a square wave output whose
frequency is determined by circuit constants or by an external synchronizing
voltage. |
| Asymmetrical Waveform |
1) A current or voltage waveform that has unequal excursions
above and below the horizontal axis or whose axis of symmetry is offset
from the zero axis (DC offset). 2) A current or voltage waveform that's
negative going half cycle differs in time from its positive going
half cycle. |
| Asynchronous |
A condition where circuit operating frequency is determined
independent of a reference source. |
| Attenuation |
Decrease in amplitude or intensity of a signal. |
| Audible Noise |
Frequencies that can be detected by the human ear produced
by the battery charger and/or inverter and measured in decibels (a
measure of intensity). The acoustical noise. |
| Auto-retransfer |
A transfer from the "alternate source" position
of a static switch to the "inverter" position without operator
intervention. |
| Auto-retransfer Circuit |
Electronic circuit which simulates the operation of
"Inverter to load" pushbutton. |
| Auto-transfer |
A Transfer from the "Inverter." position of
a static switch to the alternate source position without operator
intervention. |
| Auto-Transformer |
A transformer whose primary and secondary are electrically
connected. |
| Automatic Transfer |
A transfer is made by the UPS without operator/user
involvement and is usually based upon the status or condition of the
input/output AC power. |
| Auxiliary Contacts |
An accessory attached to a circuit breaker or magnetic
switch having low ampacity contacts that operate coincident with the
on-off-trip operation of the main device and to provide secondary
circuit functions, as lights, control signals, or interlocking functions. |
| Average Value |
1) The value of the function or quantity averaged over
a full cycle unless otherwise specified. The value of alternating
current or voltage of sine wave form that is found by dividing area
under one alternation by distance along X axis between 0 and 180'. |
Backup Power Supply
|
A power supply used to provide alternate system power
in the event the primary power source fails or is unable to continue
providing adequate system power. |
| Base Control Circuit |
The circuit used to develop and control the timing signals
for a transistorized inverter bridge (used in pulse-width modulated
inverters). |
| Battery |
One or more electrically connected cells of a device
that transforms chemical energy into electrical energy. |
| Battery Back-up |
1) The inverter/battery combination providing support
to maintain function of selected output devices upon loss of commercial
power. 2) Quantitatively, the calculated time duration this support
is to be available. |
| Battery Charger |
A device for changing alternating-current power to direct-current
power for the purpose of charging a battery. |
| Battery Jar |
One battery unit containing one cell or a number of
cells. |
| Battery Rack |
A rigid support of one or more levels (tiers or steps)
upon which a bank of stationary batteries are located. Also called
a battery stand. |
| Battery Voltage |
The total voltage between the positive and negative
terminals of the battery. In lead-acid batteries the nominal open
circuit voltage is stated to be two volts per cell. |
| Bell Alarm |
An accessory attached to a circuit breaker having form
C contacts that toggle only when the circuit breaker is in the tripped
position. |
| Binary |
The numbering system having a radix of two. This system is the
foundation for all digital technology since it requires only two
conditions for its use: energized vs. de-energized, magnetized vs.
de-magnetized, some voltage level vs. no voltage, etc. The two numbers
used in this system are one and zero, and the position of each digit
represents the power of two to which that digit is taken.
|
| Bipolar |
Having two poles, polarities or directions. |
| Bipolar Transistor |
A junction transistor having both majority and minority
charge carriers. |
| Blackout |
See AC Blackout. |
| Bleeder Resistor |
A resistor that allows a small current drain on a power
source to discharge filter capacitors or to stabilize an output. |
| Blocking Diode |
A device that prevents the flow of current from the
UPS rectifier to the battery, but permits the flow of current from
the battery to the UPS inverter. |
| Boost Charge |
Charge, generally at high-rate, for a limited period
to achieve full capacity in all cells of a battery. |
| Boost Transformer |
May be an isolating transformer or an autotransformer
that provides a means of raising a supply line voltage, usually by
a small amount of 20% or less. |
| Branch Circuit |
That portion of the wiring installation between the
final overcurrent device protecting the circuit and the line connection. |
| Branch Circuit Protection |
An overcurrent protection circuit or device that protects
the branch circuit. |
| Break-Before-Make Switch |
A switch which while transferring between two sources
goes through a neutral position where momentarily neither source is
connected to the output and an interruption occurs on the output. |
| Break-Before-Make Transfer |
A transfer between two sources when a momentary break
on the output occurs. |
| Break Transfer |
As pertaining to a switch or static switch, transfer
between two sources where the output momentarily loses continuity
to either source and an interruption to the output voltage occurs. |
| Breakdown Voltage |
1) The voltage level which causes insulation failure.
2) The reverse voltage at which a semiconductor device changes its
conductance characteristics. |
| Breaker |
A device designed to open and close a complete circuit
by non-automatic means (like a switch), and to open the circuit automatically
on a predetermined overload of current, without injury to itself. |
| Breaker-Automatic |
A circuit protection device which will automatically
open or break continuity |
| Bridge Circuit |
Circuit with series-parallel groups of components. |
| Bridge Converter |
A power conversion circuit with the active elements
connected in a bridge configuration |
| Bridge Rectifier |
Full-wave rectifier circuit employing two or more rectifiers
in a bridge configuration. |
| Brownout |
The condition created during peak usage periods when
electric utility companies intentionally reduce their line voltage
by approximately 10 to 15 percent to counter excessive demand. |
| BTU |
For British Thermal Units, this is the unit of quantity
of thermal energy in the United States, and is the quantity of heat
or thermal energy required to raise the temperature of one pound of
pure water one degree F. With respect to power, one watt is equal
to 3.412 BTU per hour. |
| Buck Transformer |
A transformer that provides a means of lowering a supply
line voltage, usually by a small amount such as 20% or less. |
| Bulk Capacitor |
The energy storage capacitor at the front end of a regulator. |
| Bulk Voltage |
The voltage across a bulk capacitor. |
| Burn In |
The operation of newly fabricated units or systems prior
to their ultimate application intended to stabilize their characteristics
and identify early failures. See Infant mortality. |
| Bus |
The common primary conductor of power from a power source
to two or more separate circuits. |
| Bus Transfer Switch |
Any switch (mechanical, electromechanical, or static)
used to transfer a load from one source of AC supply power to another,
often upon loss of power from the initial source. |
| Bypass |
A path where the Commercial AC Power can be routed from
the AC input to the AC output of an UPS, bypassing the Battery/inverter
sections. |
| Bypass Source |
See Alternate Source. |
| Bypass Transformer |
A transformer that provides alternating current power
to the UPS loads when the UPS equipment fails, is temporarily overloaded,
or is out of service for maintenance. |
Capacitance
|
Inherent property of an electric circuit or device that
opposes change in voltage. Property of circuit whereby energy may
be stored in an electrostatic field. |
| Capacitance, Distributed |
The capacitance in a circuit resulting from adjacent
turns on coils, parallel leads and connections. |
| Capacitive Coupling |
Coupling resulting from the capacitive effect between
circuit elements. |
| Capacitive Reactance (XC) |
Opposition to AC as a result of capacitance. |
| Capacitor |
A device that stores a charge. A simple capacitor consists
of two conductors separated by a dielectric. |
| Capacitor Forming |
A process used in manufacture of aluminum electrolytic
capacitors to deposit an oxide layer on the anode by application of
a specific voltage over a given period of time at elevated temperature. |
| Capacitor Input Filter |
Filter employing capacitor as its input. |
| Capacitor Shelf Life |
Aluminum electrolytic capacitors (chemical condensers)
exhibit deterioration and increased leakage current when stored. The
stated shelf life differs between manufacturers, but the consensus
is about 24 months, extendable to 60 months by periodic "reforming."
Reforming is a process where voltage is applied with the capacitor
temperature elevated (an oven), and if the capacitor meets certain
pass/fail criteria (must have an acceptably low leakage current),
it may be returned to storage. |
| Cathode Terminal |
1) In semi-conductors, the negative terminal by which
current leaves the device. 2) In semiconductor diodes, the terminal
that is negative with respect to the other terminal when the diode
is biased in the forward direction. |
| Cell |
1) The basic electrochemical unit used to generate or
store electrical energy. A cell consists of two electrodes of dissimilar
material isolated from one another electronically, in a common ironically
conductive electrolyte. 2) An electrochemical system which converts
chemical energy into electrical energy and also the reverse for rechargeable
units. |
| Cell Polarization |
The difference between the e voltage of a cell I as
a result of current flow, and its voltage at a reference state which
may be an equilibrium or steady state value. |
| Cell Reversal |
Reversal of polarity of a cell due to over discharge.
|
| Cell Voltage |
The DC voltage potential between the individual positive
and negative terminals of a cell in a battery. |
| Center Tap |
Connection made to center of an electronic device. |
| Charge |
1) The conversion of electrical energy, provided in
the form of a current from an external source, into chemical energy
within a cell or battery. 2) The potential energy stored in a capacitive
electrical device. 3) The conversion of electrical energy to chemical
energy in a cell or battery. |
| Charge/Discharge Cycle |
A sequence of a charge and subsequent discharge. |
| Charge Equalization |
Bringing all of the cells in a battery to the same state
of charge. |
| Charge Rate |
The current applied to a secondary cell or battery to
restore its capacity. This rate is commonly expressed as a multiple
of the rated capacity of the cell or battery. For example; the C/1
0 charge rate of a 500-Ah cell or battery is expressed as: c/10 rate
= 500 Ah/10 = 50 A |
| Charge, State of |
Condition of cell in terms of the rated capacity remaining
in the cell at a given point in time. |
| Charge Voltage |
The voltage applied to a cell during charge. |
| Charger |
Constant voltage or constant current device used to
charge a cell or battery. |
| Charger (Battery) |
An electrical device or circuit that is capable of restoring
the charge in a storage battery. |
| Charging |
Process of supplying electrical energy for storage. |
| Charging Temperature Coefficient |
The factor by which the charge voltage must be adjusted
for a given change in voltage. |
| Chassis Ground |
The voltage potential of the chassis. |
| Chatter |
Intermittent opening and closing of relay contacts resulting
from voltage fluctuation to its coil. |
| Chip |
See Integrated Circuit. |
| Choke Coil |
An inductor. k |
| Choke, RF |
Choke coil with a high impedance at radio frequencies. |
| Circuit Input Filter |
A filter employing an inductor W or an inductor/capacitor
(L/C) as its input. |
| Circular Mil |
Cross-sectional area of a conductor one mil. in diameter. |
| Circulating Current |
See Ground Loop |
| Clamp Circuit |
A circuit that biases a voltage waveform to a specified
voltage level. |
| Clamp Diode |
A diode in either a clipper or clamp circuit. |
| Clock |
An oscillator producing timing pulses to synchronize
various elements of a system. In switching mode power supplies, a
clock is used to produce the power pulses that are modulated to control
power transfer. In digital interfaces that communicate on a bus (such
as the IEEE-0488) a clock is used to synchronize the date transfer
and commands. |
| Closed Loop Gain |
In a feedback control circuit, the increase in value
of an output signal due to the effects on it of various other components
or signals in the circuit. See also GAIN. |
| Closed-Circuit Voltage (CCV) |
The potential voltage at the terminals of an electrical
device when current is flowing. |
| Collector |
1) Electronic connection between the cell electrode
and the external circuit. 2) ln a transistor, the semiconductor section
which collects the majority carriers. |
| COM |
See Commercial AC Power |
| Commercial AC Power (COM) |
Power furnished by an electric power utility company
(also referred to as utility power): when available, it is usually
the prime power source. Prime power is that source of supply of electrical
energy utilized by the user and is available continuously day and
night. Besides utilities, another power source is the user's own generator. |
| Commercial AC Power |
Normal power source used to power the alternate source
and rectifier inputs to the UPS. Also see Alternate Source and Rectifier
Input. |
| Common-Mode Noise |
The component of noise voltage that appears equally
and in phase on conductors relative to a common reference. |
| Commutation |
Transfer of unidirectional current between circuit elements.
(The transfer of current between various paths of a circuit). |
| Comparator |
A DC amplifier, circuit, having only two logic output
states, for comparing the amplitudes of two analog variables, or of
such a variable and a constant, such that the logic signal output
uniquely determines which input is larger at all times. |
| Compensation |
The addition of circuit elements to assist in stabilization
of a control loop. |
| Component |
An element in an electrical circuit. |
| Conductor |
Material that permits free motion of large number of
electrons. |
| Connector |
A mechanical device used to link conductors. |
| Constant Current Charge |
1) A charge during which the current is maintained at
a steady state value. 2) A method of charging a cell by applying a
non-varying current to the cell. |
| Constant Current Limiting Circuit |
Current-limiting circuit that holds output current at
some maximum value whenever an overload of any magnitude is experienced. |
| Constant Current Power Supply |
A power supply that regulates its output current, within
specified limits, against changes in line, load, ambient temperature
and time. |
| Constant Voltage Charge |
1) A charge during which the voltage across the battery
terminals is maintained at a steady state. 2) A method of charging
a cell by applying a nonvarying voltage to the cell. |
| Constant Voltage Power Supply |
A power supply that regulates its output voltage within
specified limits, against changes in line, load, ambient temperature
and time. |
| Constant Voltage Transformer |
Maintains an almost constant voltage ratio over the
range from zero to rated output. |
| Contact Chatter (or Contact Bounce, Switch Bounce)
|
When two mechanical contacts close, they make and break
several times before reaching a stable closed condition. Bounce can
also be caused by external vibration or shock. |
| Contacts |
Elements used to mechanically make or break a circuit. |
| Continuity of Load Power |
The availability of load power within the limits specified
for the load. |
| Continuous Duty |
A requirement of service that demands operation at a
substantially constant load continuously for an indefinitely long
time with no off or rest periods. See also Intermittent Duty |
| Control |
The means of regulating the operation of a piece of
equipment. |
| Control Circuit |
The circuit that carries the electric signals directing
the performance of a control device, but that does not carry the power
that the device controls. |
| Control Loop |
A feedback circuit used to control an output signal.
See also Loop |
| Control Power Supply |
The power supply developing the correct voltage at the
appropriate current to power the control logic circuits for a system. |
| Convection-Cooled Power Supply |
A power supply cooled exclusively from the natural motion
of a gas or a liquid over the surfaces of heat dissipating elements. |
| Converter |
A device that changes the value of a signal or quantity.
DC-DC: A device that delivers DC power when energized from a DC source.
FLY-BACK: A type of switching power supply circuit. See also Flyback
Converter -Forward: A type of switching supply circuit. See also Forward
Converter |
| Cooling |
The process of removing heat dissipated by a power supply
during transformation and regulation. |
| Core |
Magnetic material serving as a path for magnetic flux. |
| Core Saturation |
The tendency of molecules in an iron core to orient
in one direction due to the application of direct current. |
| Counter/Counting circuit |
A digital circuit which counts and stores numbers of
events. |
| Coupling |
The characteristic of isolated circuit elements to interact
with one another. |
| Crest Factor |
For a periodic waveform such as a sine wave, it is the
ratio of its crest (the peak, maximum) value to its RMS (root-mean-square)
value. |
| Crowbar |
An overvoltage protection circuit which rapidly places
a low resistance shunt across the power supply output terminals if
a predetermined voltage is exceeded. |
| CSA |
Canadian Standards Association, or a product testing
and approval agency in Canada. |
| Current (1) |
The rate of transfer of electrical energy measured amperes.
(One "international" ampere will deposit silver from a silver
nitrate solution at the rate of 0.00111800 grams per second An "international"
ampere, in turn, is defined as 0.99985 OUT "absolute" amperes,
one coulomb Current Foldback Limiting and Current Limiting per second.) |
| Current Limit Knee |
The point on the plot of current vs. voltage of a supply
at which the current starts to foldback. |
| Current Limit (Control) |
A control function that prevents current from exceeding
its prescribed limits. |
| Current Limiting Circuit |
An electronic overload protection circuit that limits
the maximum output current to a preset value. Limiting the output
current from a circuit invokes a limit on the input current to the
circuit as well. |
| Current Sensing Resistor |
A resistor placed in series with the load to develop
a voltage proportional to load current. |
| Current Transformer |
1) Instrument Transformer: Intended to have its primary
winding connected in series with the conductor carrying the current
to be measured or controlled. 2) Metering: Designed for use in the
measurement or control of current. Its primary winding may be single
turn or bus bar, and is connected in series with the load. 3) Power
and Distribution Transformer: Intended to have its primary winding
connected in series with the conductor carrying the current to be
measured or controlled. (In window type current transformers, the
primary winding is provided by the line conductor and is not an integral
part of the transformer.) |
| Cutoff Voltage |
1) The cell or battery voltage at which the discharge
is terminated. The cutoff voltage is specified by the cell manufacturer
and is generally a function of discharge rate. 2) Voltage at the end
of discharge. Cell voltage below which the UPS will not operate or
below which operation is not recommended. |
| CVT |
Abbreviation for Constant Voltage Transformer. See Ferroresonant. |
| CVT Capacitor |
Those capacitors in the secondary tank circuit of the
CVT, for the purpose of producing ferroresonance. |
| Cycle |
1) In alternating current, one cycle is one 3600 transition
of the waveform. 2) One complete battery charge and discharge. |
DB (db)
|
A dimensionless unit for representing the ratio between
two values of power. |
| DC Link |
The direct-current power interconnection between rectifier
or rectifier/charger and inverter sections. |
| DC Offset Voltage |
The measure of the voltage by which a waveforms negative
and positive excursions are offset from the zero axis. |
| Debug |
The process of detecting and correcting errors. |
| Deenergize |
Remove power. |
| Deep Discharge |
1) Withdrawal of at least 80% of the rated capacity
of a cell or battery. 2) Discharge of a battery to below the specified
voltage cutoff before the battery is replaced or recharged. |
| Delay on Operate |
Electromechanical relay that is normally deenergized
and when voltage is applied to its coil, delays by some fixed or adjustable
time interval before operating. |
| Delay on Release |
1) Electromechanical relay that is normally energized
and when voltage is supplied to a timing input drops out after some
fixed or adjustable time interval. 2) A relay that energizes the moment
voltage is applied then drops out (deenergizes) after some time delay. |
| Depth of Discharge |
1) The ratio of the quantity of electricity (usually
in ampere-hours) removed from a secondary cell or battery on discharge
to its rated capacity. 2) The percent of rated capacity to which a
cell or battery is discharged. 3) Capacity discharged from a battery
in relation to the rated capacity. May be expressed as a percentage.
4) The percent of rated capacity removed from a cell during a discharge. |
| Deviation |
The difference between the actual value of a quantity
and the ideal or desired values. |
| Dielectric |
An insulating material between conductors that is resistant
to electric current flow. |
| Dielectric Tests |
Tests which consist of the application of a voltage
higher than the rated voltage for a specified time to verify the dielectric
withstand strength of insulation materials and spacing. |
| Dielectric Withstand Strength |
The specified voltage or potential gradient below which
a dielectric material will continue to resist electrical current flow. |
| Difference Voltage |
The voltage difference between two sources. When referring
to a static switch operation it is the voltage between one of the
phases of the alternate source and the corresponding phase of the
inverter. During synchronization the difference voltage between each
of the phases of the alternate source and the corresponding inverter
source should be at a minimum or null value. |
| Differential Amplifier |
An amplifier whose output signal is proportional to
the algebraic difference between two input signals. |
| Differential Mode Noise |
The component of noise, excluding common-mode noise,
that is measured between two lines with respect to a common reference
point. The value is the difference of the noise components on the
two lines. |
| Differential Voltage |
The difference in voltages at two points as measured
with respect to a common reference. |
| Diode |
A two-element device containing a cathode and an anode
that permits flow in one direction and blocks flow from the other. |
| Direct Current (DC) |
Flow of electrons in one direction. In text, "DC". |
| Discharge |
1) The conversion of the chemical energy of a cell or
battery into electrical energy and withdrawal of the electrical energy
into a load. 2) Withdrawal of electrical energy from a cell or battery,
usually to operate connected equipment. 3) Characteristic of a capacitive
device to release stored energy. 4) The conversion of chemical energy
to electrical energy in a cell or battery. |
| Discharge Rate |
1) The rate, usually expressed in amperes, at which
electrical current is taken from the cell or battery. 2) The current
at which a cell or battery is discharged. 3) The value of the current
in amperes at which a battery is discharged expressed as a fraction
or multiple of the rated capacity in ampere-hours of the cell, e.g.,
C/5 or 5C. 4) See C/X Rate. (C=rated capacity; X=hours of discharge). |
| Displacement Factor |
The displacement component of power factor; the ratio
of the real power of the fundamental wave to the apparent power of
the fundamental wave. |
| Drift |
A change in output over a period of time independent
of input, environment or load. |
| Duration |
The time interval between the first and last instants
at which the instantaneous amplitude reaches a stated fraction of
the peak pulse amplitude. |
| Duty Cycle |
The ratio of time on to time off in a recurring event. |
| Dynamic Load |
A load that rapidly changes from one level to another.
To be properly specified, both the total change and the rate of change
must be stated. |
Earth
|
An electrical connection to the earth frequently using
a grid or rod(s). See also Ground |
| Effective Value |
The value of a waveform that has the equivalent heating
effect of a direct current. For sine waves, the value is.707 x Peak
Value; for non-sinusoidal waveforms, the Effective Value = RMS (Root
Mean Square) Value. |
| Efficiency |
1) The ratio of output power to input power expressed
in percentage. 2) The ratio of the output of a secondary cell or battery
on discharge to the input required to restore it to the initial state
of charge. (See also Ampere-Hour Efficiency, Voltage Efficiency and
Watt Hour Efficiency.) |
| Electricity |
Property of fundamental particles of matter that have
a force field associated with them to gain or lose electrons. |
| Electro-Mechanical Switch |
An magnetically transferred device such as a relay,
contactor, transfer switch, etc. |
| Electrolyte |
The conducting medium within an electrochemical cell
that provides the ion transport mechanism between positive and negative
electrodes. |
| Electrolytic Capacitor |
A device that contains two electrodes separated by an
electrolyte. |
| Electromagnet |
A device consisting of a ferromagnetic core and a coil
that produces appreciable magnetic effects only when an electric current
exists in the coil. |
| Electromagnetic Interference (EMI) |
Any electronic disturbance that interrupts, obstructs,
or otherwise impairs the performance of electronic equipment. |
| Electromotive Force (EMF) |
Force that causes free electrons to move in a conductor.
Unit of measurement is the volt. |
| Electron |
Negatively charged particle. |
| Electron Volt |
A measure of energy. The energy acquired by an electron
passing through a potential of one volt. |
| Electronic Power Converter |
An electronic device for changing power in one of the
following ways: AC/DC power converters, DC/AC power converters, AC/AC
power converters, or DC/DC power converters. |
| Electronic Power Switch |
An electronic device which can be controlled to interconnect
power circuits. |
| Electrostatic Shield |
A conductive screen that shunts induced electrical energy
to ground. |
| Emergency Power Off (EPO) |
A circuit required by the National Electric Code for
certain applications that provides for a remote-controllable disconnecting
means to remove power to all equipment in a room. |
| EMI Filter |
A circuit composed of reactive and resistive components
for the attenuation of radio frequency components being emitted from
a power supply. See also EMI |
| End Voltage |
1) The prescribed voltage at which the discharge (or
charge, if end-of-charge voltage) of a cell or battery may be considered
complete (also cutoff voltage). 2) The battery or cell voltage at
the end of a discharge. The battery is so dimensioned that the end
voltage is never less than the lowest voltage at which a system can
operate. |
| Energy |
Output capability; ampere-hour capacity times average
closed-circuit discharge voltage, expressed as watt-hours. |
| Equalization |
The process of restoring all cells in a battery to an
equal state of charge. |
| Equalizing Charge (Storage Battery) |
An extended charge to a predetermined measured value
that is given to a storage battery to insure the complete restoration
of the active materials in all the plates of all the cells. |
| Equalizing Charge |
An extended charge to ensure complete charging of the
entire cell in a battery. |
| Equivalent Circuit |
An electrical circuit that models the fundamental properties
of a device or circuit. |
| Equivalent Load |
An electrical circuit that models the fundamental properties
of a load. |
| Error Signal |
The output voltage of an error amplifier produced by
the difference between the reference and the input signal times the
gain of the amplifier. |
| Error Voltage |
The output voltage of the error amplifier in a control
loop. |
Failure
|
The termination of the ability to perform a required
function. |
| Failure Mode |
The way in which a device has ceased to meet specified
minimum requirements. |
| Fan Cooled |
A method of forced-air cooling used to maintain design
temperatures. |
| Farad |
Unit of measurement of capacitance. A capacitor has
a capacitance of one farad when a charge of one coulomb raises its
potential one volt. C=Q/E |
| Fault |
Partial or total failure of the insulation system. |
| Fault Current Availability |
The current flow that can occur as a result of a zero
impedance fault. |
| FE Change Circuit |
FE is for Float/Equalize. |
| Feedback |
The process of returning part of the output signal of
a system to its input. |
| Ferroresonance |
1) The steady-state mode of operation that exists when
an alternating voltage of sufficient magnitude is applied to a circuit
consisting of capacitance and ferromagnetic inductance causing changes
in the ferromagnetic inductance which are repeated each half cycle.
2) The property of a transformer design in which the transformer contains
two separate magnetic paths with limited coupling between them. The
output contains a resonating tank circuit and draws power from the
primary to replace power delivered to the load. |
| Ferroresonant Power Supply |
1) The effect obtained by the limiting action of the
saturation characteristic of the magnetic material in a ferroresonant
circuit, which regulates the output voltage over a specified range
of input voltages and a specified frequency of excitation. 2) A regulated
power supply that uses a resonant circuit, with a capacitor in one
of the secondaries that resonates with the inductance of the transformer.
Ferroresonant power supplies are designed to operate at a given input
frequency. |
| Field Effect Transistor (FET) |
Transistor in which the resistance of the current path
from source to drain is modulated by applying a transverse electric
field between two electrodes. |
| Filter |
One or more discrete components positioned in a circuit
to attenuate signal energy in a specified band of frequencies. |
| Final Charging Voltage |
The voltage which a battery reaches at the end of a
charging operation.In the case of constant voltage charging, this
voltage is determined by the setting of the charging equipment. |
| Final Discharge Voltage |
The low end voltage to which the batteries are permitted
to discharge. |
| Flame Arresting Vent |
A special design of a wet cell vent which provides protection
against internal explosion when the cell or battery is exposed to
a naked flame or external spark. |
| Flip Flop |
A device or circuit which can maintain either of two
stable conditions and with one or more inputs which can cause it to
switch over from one of those conditions to the other. |
| Float Charge |
1) A method of maintaining a cell or battery in a charged
condition by continuous, long-term, constant-voltage charging, at
a level sufficient to balance self-discharge. 2) Method of recharging
in which a secondary cell is continuously connected to a constant-voltage
supply that maintains the cell in fully charged condition. 3) To maintain
the capacity of a cell by applying a constant voltage. |
| Float System |
A UPS system where the batteries are floated at a regulated
DC voltage by a battery charger having sufficient capacity to power
the fully loaded UPS and recharge discharged batteries. |
| Float Voltage |
The voltage required for retaining a charged battery
in a fully charged condition. This is also known as float charging. |
| Flooded Cell |
A cell design which incorporates an excess amount of
electrolyte. |
| Flux (Greek letter PHI) |
Total number of lines of magnetic force. |
| Flux Density (B) |
Number of lines of flux per cross-sectional area of
a magnetic circuit in Gauss. |
| Foldback Current Limiting |
A power supply output protection circuit whereby the
output current decreases with increasing overload, reaching a minimum
at short circuit. This minimizes internal power dissipation under
overload conditions. Holdback current limiting is normally used with
linear regulators. |
| Form "C" Contacts |
Contacts from an electromechanical relay or switching
device which from a Common connection can select either a Normally
Open or Normally Closed connection. |
| Four Wire Output |
A two or three phase AC source with four output leads.
Refer to Four Wire Input. |
| Free-running Frequency |
The operating frequency of an oscillator circuit which
is not being influenced by error correcting signal or whose frequency
is determined only by circuit constants. |
| Frequency |
Number of cycles per second measured in hertz (Hz). |
| Frequency Response |
Rating of a device indicating its ability to operate
over a specified range of frequencies, e.g., gain-frequency characteristics
of an amplifier. |
| Frequency Modulation |
The cyclic or random dynamic variation or both, of instantaneous
frequency about a mean frequency during steady state electrical system
operation. |
| Frequency Tolerance |
A deviation from a standard frequency often expressed
in percent. |
| Full-Bridge Converter |
A power switching circuit in which four power switching
devices are connected in a bridge configuration to drive a transformer
primary. |
| Full-Bridge Rectifier |
A rectifier circuit that employs four diodes per phase. |
| Full-Wave Rectifier |
Rectifier circuit that produces a DC output for each
half cycle of applied alternating current. |
| Functional Unit |
A system element that performs a task required for the
successful operation of the system. |
| Fuse |
Safety protective device that permanently opens an electric
circuit when overloaded. See also Overcurrent Device, Overcurrent
Protective Device. |
| Fuse Clearing Curve |
The time current characteristic curve that indicates
the functions over time of the fuse. |
| Fuse Coordination |
In thyristors, the fuse time-current characteristic
curve is selected to protect the semiconductor from damage. In distribution
systems, the fuse or circuit breakers are each selected so that interruption
of any branch does not interrupt the source. |
Gap
|
A non-magnetic segment in the magnetic path in a transformer
or choke. |
| Gassing |
The evolution of gas from one or more of the electrodes
in a cell. Gassing commonly results from local action (self-discharge)
or from the electrolysis of water in the electrolyte during charging. |
| Gate |
1) A device or element that has the ability to block
or pass a signal. 2) A device having one output channel and two or
more input channels that performs a logic function. 3) A control electrode
in a semiconductor device such as a triac, or FET. |
| Glitch |
1) An undesired transient voltage spike occurring on
a signal. 2) A minor technical problem arising in electrical equipment. |
| Ground |
A conducting connection, whether intentional or accidental,
by which an electric circuit or equipment is connected to earth, or
to some conducting body that serves in place of earth. |
| Ground Bus |
A bus to which individual grounds in a system are attached
and that in turn is grounded at one or more points. Also see Single
Point Common Ground and Isolated Ground. |
| Ground Grid |
Interconnected bare conductors arranged in a pattern
over a specified area, laid out on or below the earth's surface. |
| Ground Loop |
A condition that causes undesirable voltage levels when
two or more circuits share a common electrical return or ground lines.
Also see Neutral Electrical Return. |
| Ground Rod |
A metallic rod, commonly copper clad, driven into the
earth to serve as a ground terminal. |
| Grounded |
Connected to or in contact with earth or connected to
some extended conductive body which serves instead of the earth. |
| Grounding |
A permanent and continuous conductive path to earth
with sufficient ampacity to carry any fault current liable to be imposed
on it, and of a sufficiently low impedance to limit the voltage rise
above ground. |
Half-Wave Rectifier
|
A circuit element, such as a diode, that rectifies only
one-half the input AC wave to produce a pulsating DC output. |
| Hall Effect |
Magnetic fields have an effect on semiconductors in
that a magnetic field at a right angle to current with deflect charge
carriers toward one surface of the crystal, thereby producing a positive
potential on that surface for a p-type semiconductor or a negative
potential for an n-type material. |
| Hiccup |
A transient condition that momentarily confuses a control
loop. |
| High Line |
Highest specified input operating voltage. |
| High Rate of Charge |
A slightly higher DC voltage supplied to batteries after
a discharge to reduce the recharge time interval. Note that this term
differs from the term "Equalize" in that a high rate charge
may be permitted by the battery manufacturer for a battery type that
may not be "equalized" (Sealed maintenance-free types). |
| Holding Current |
A value indicating the minimum load operating current
of an electromechanical device, usually stated in milliamperes. |
| Holdup Time |
The time under worst case conditions during which a
power supply's output voltage remains within specified limits following
the loss or removal of input power. Often called ride-through. |
| Hum |
Audible noise from a magnetic device due to magnetostrictive
activity of the core at twice line frequency. |
| Humidity |
The amount of moisture in the air, measured in percent
relative humidity. For UPS 40 to 95% non-condensing relative humidity
is the acceptable range, unless otherwise specified. |
| Hysteresis |
1) The property of a magnetic substance that causes
magnetization to lag behind the force that produces it. 2) A variable
input voltage threshold determined by the logic state of the output
of the circuit. |
| Hysteresis Loop |
A closed curve that 'Shows, for each value of magnetizing
force, two values of the magnetic flux density in a cyclically magnetized
material: one when the magnetizing force is increasing, the other
when it is decreasing. |
I IC
|
See Integrated Circuit. |
| Impedance (Z) |
The opposition to the flow of an alternating current.
Impedance consists of resistance R, inductive reactance XL, and capacitive
reactance XC. |
| In Phase |
When comparing two AC sources, the transitions of each
phase of one source are in step with the transitions of the corresponding
phases of a second source. |
| Indicating Fuse |
See Actuator Fuse |
| Inductance (L) |
The inherent reactive property, measured in henrys,
of an electric circuit or circuit element that opposes a change in
current flow. Hence, inductance causes current changes to lag behind
voltage changes. See also Henry |
| Inductive Circuit |
Circuit in which an EMF is produced by a changing current. |
| Inductive Load |
Electrical devices that create a magnetic field when
energized, such as motors, solenoids, coils, valves, and transformers.
An inductive load can exhibit an inrush or lock-rotor current, when
energized, many times its normal running or steady state current.
When deenergized the magnetic field collapses generating a high voltage
transient which can cause arcing across contacts as well as damage
to circuits if not suppressed. |
| Inductive Reactance (XL) |
Opposition to a changing current as a result of inductance.
XL=27cFL |
| Inductor |
A coil or component with the properties of inductance. |
| Infant Mortality |
That early period of equipment life during which the
failure rate of some items is decreasing rapidly. This is also called
the early failure period or break-in period. |
| Input Impedance |
The impedance of the input terminals of a circuit or
device, with the input disconnected. |
| Input Isolation |
Refers to the use of an isolation transformer at the
input to the rectifier and/or battery charger section of the UPS.
This serves to attenuate noise at the inverter, isolates from surges,
and prevents the batteries from being referenced to Ground. |
| Input Surge |
See Inrush Current |
| Input Voltage Range |
The range of input voltage values for which a power
supply or DC-AC Inverter operates within specified limits. |
| Inrush Current |
1) A current higher than its steady state value drawn
by a device when energized or activated, 2) the peak instantaneous
input current drawn by a power supply at turn on, or 3) the maximum
current from turn on to a specified limit of duration. 4) Comments:
Lamps, electric motors, solenoids, contactors, valves, and capacitors
have inrush currents that exceed normal operating current. |
| Instantaneous Value |
The measured value of a signal at a given moment in
time. |
| Insulation Resistance |
The value of resistance offered by an insulating material
to an impressed voltage. The device used to measure insulation resistance
is the Megger, which typically applies 50OVDC to the insulation. |
| Integrated Circuit 00 |
A combination of active and passive circuit elements
contained on a single semiconductor substrate. |
| Internal Impedance |
The impedance exhibited by a circuit element or component. |
| Internal Resistance |
1) The resistance exhibited by a circuit element or
component. 2) Opposition to direct current flow within a cell, with
the cell as source, causing a drop in closed-circuit voltage proportional
to the current drain from the cell. |
| Interruption |
Either momentary or long-term ceasing of current flow
through an electronic circuit. |
| Inverter |
1) A machine, device, or system that changes direct-current
power to alternating-current power. 2) A circuit, circuit element
or device that inverts the input signal. |
| Isolated Regulated Charger |
A battery charger employing an input isolation transformer
as well as maintaining a regulated DC output. |
| Isolation |
The electrical separation between two circuits, or circuit
elements. |
| Isolation Transformer |
A transformer with a one-to-one turns ratio. See Also
Step-Down Transformer, Step-Up Transformer, Transformer |
| KVA |
Symbol for Kilovolt Amperes, or thousands of volt amperes. |
| KW |
|
| KWHr |
Symbol for kilowatt-hour. |
| Lagging Angle |
Angle current lags voltage in inductive circuit. |
Latch
|
1) A logic circuit that, once set, maintains the output
at some fixed state until reset. 2) In relay logic, a momentary initiation
will hold the device energized through a holding contact. |
| Latching Alarm |
A latch initiated by an alarm condition, requiring a
reset command before returning to normal operation. |
| Latching Relay |
A relay that mechanically latches until mechanically
or electrically reset. |
| Lead Acid Cell |
Secondary cell which uses lead peroxide and sponge lead
for plates, and sulfuric acid and water for electrolyte. |
| Leading Angle |
Angle current leads voltage in capacitive circuit. |
| Light-Emitting Diode (LED) |
A semiconductor device that radiates in the visible
spectrum when energized by an electric current. Color is determined
by the electroluminescent characteristics of the materials used in
fabricating the devices, and by the addition of various dopants. For
example, copper-doped zinc sulfide emits light in the 620 nanometer
(green) range, the area of peak sensitivity of the human eye. |
| Line Conditioner |
A circuit or device designed to improve the quality
of an AC line. |
| Line Frequency Regulation |
The percentage change in output for a specified change
in the line frequency at specified load values, with all other factors
constant. |
| Line Regulation |
The percentage change in output due to the input voltage
varying over its specified limits, at specified load values, with
all other factors constant. |
| Line Regulator |
Power conversion equipment that regulates and/or changes
the voltage of incoming power. |
| Line Transient |
A disturbance outside the specified operating range
of an input or supply voltage. |
| Linear |
1) In a straight line 2) A mathematical relationship
in which quantities vary in direct proportion to one another, the
result of which, when plotted, forms a straight line. |
| Linear AC Load |
A load whose current waveform is sinusoidal when supplied
a sinusoidal voltage. |
| Load (AC) |
1) A device or devices which receive power from the
AC output of the UPS. 2) Capacitance, resistance, inductance or any
combination thereof, which, when connected across a circuit determines
current flow and power used. |
| Load (DQ |
The inverter and discharged batteries are seen as DC
loads to the battery charger. |
| Load Regulation |
1) STATIC The change in output voltage as the load is
changed from specified minimum to maximum and maximum to minimum,
with all other factors held constant. 2) DYNAMIC The change in output
voltage expressed as a percent for a given step change in load current.
Initial and final current values and the rates of change must be specified.
The rate of change shall be expressed as current/unit of time, e.g.,
20 amperes A/u second. The dynamic regulation is expressed as a +/ |
| Load Sharing |
The simultaneous supplying of power to a load from two
or more sources. |
| Load Transfer Time |
The time required for the transfer of the load from
one power source to another. |
| Logic Ground |
Common return or reference point for logic signals.
May or may not be referenced to ground. |
| Logic Inhibit/Enable |
1) A referenced or isolated logic signal that turns
a power supply output off or on. 2) A circuit which either locks out
or activates another circuit. |
| Logic Signal |
An instruction that executes an operation to perform
a specified function. |
| Low-Voltage System |
An electric system having a maximum root-mean-square
alternating-current voltage of 1 OOOV or less. |
| Low Line |
Lowest specified input operating voltage. |
| Low Voltage Cutoff |
The pre-adjusted voltage point where the inverter will
shut itself off during battery discharge to prevent damage to the
UPS and to the batteries. This voltage point is equivalent to the
end volts per cell as specified by the battery manufacturer. |
Magnetic Shunt
|
The section of the core of the ferroresonant transformer
that provides the major path for flux generated by the primary winding
current that does not link the secondary winding. In addition, the
shunts provide a major path for the flux resulting from the output
and resonating winding currents that do not link the primary winding. |
| Maintenance Bypass Switch |
A switch which either partially or totally isolates
the UPS system from the AC power source (Alternate source), but at
the same time may or may not maintain continuous alternate source
feed to the load, depending on design. |
| Maintenance Free Battery |
1) A secondary battery which does not require periodic
"topping up"' to maintain electrolyte volume. 2) A battery,
which during its specified working life needs no maintenance other
than charging, provided normal operating conditions are experiences.
3) A term used for a type of cell which may be operated without adding
water to the electrolyte during its recommended life. |
| Make-Before-Break Switch |
A switch, which while transferring between two sources,
momentarily shorts the two so that the continuity between the output
and one of the two sources is never interrupted. |
| Make-Before-Break Transfer |
A transfer between two sources; no interruption or loss
of continuity to the load occurs. |
| Manual Bypass Switch |
See Maintenance Bypass Switch. |
| Manual Transfer |
1) A transfer made by the operator/user, generally by
the movement of a switch from one position to another. 2) A transfer
from the "inverter" position to the alternate source position
or vice-versa, which is initiated by operator. |
| Master/Slave Operation |
Interconnection of two or more regulated supplies in
which one (the master) controls the other (the slave). |
| Maximum Load |
1) The highest allowable output rating specified for
any oral I outputs of a power supply under specified conditions including
duty cycle, period and amplitude. 2) The highest specified output
power rating of a supply specified under worst case conditions. |
| Mean Time Between Failure (MTBF) |
The arithmetic average of operating times between failures.
An established method of calculating MTBF is described in Mil Handbook
217. |
| Mean Time To Repair (MTTR) |
The arithmetic average of time required to complete
a repair activity. |
| Mega |
A prefix for millions, such as megohms. |
| Micro |
A prefix for one millionth, such as microfarads or microseconds. |
| Milli |
A prefix for one thousandth, such as millisecond or
millihenrys. |
| Motor Generator |
A machine made up of a gasoline, diesel, or other type
of motor mechanically coupled to and driving a generator. |
| MTBF |
Abbreviation for MEAN TIME BETWEEN FAILURE |
| MTTR |
Abbreviation for MEAN TIME TO REPAIR |
| Multimeter |
A meter capable k of measuring current, voltage and
resistance. |
| Multiple Output Power Supply |
A power supply with two or more outputs. |
| Multivibrator |
A circuit capable of assuming either one of two stable
states at a given time. |
NC
|
Normally closed. (See Normally Closed) |
| NO |
Normally open. (See Normally Open) |
| Negative Electrode |
The electrode acting as an anode when a cell or battery
is discharging. |
| Negative Rail |
The more negative of the two conductors at the output
of a power supply. |
| Negative Temperature Coefficient |
A decreasing function with increasing temperature. The
function may be resistance, capacitance, voltage, etc. |
| Neutral |
The AC return sometimes connected to ground, but which
should not be used for ground because it is a current-carrying path. |
| No Load Voltage |
Terminal voltage of battery or supply when no current
is flowing in external circuit. Also see Open Circuit Voltage. |
| Noise |
The a periodic random component on the power source
output which is unrelated to source and switching frequency. Unless
specified otherwise, noise is expressed in peak-to-peak units over
a specified bandwidth. |
| Nominal Value |
The value used to designate or identify a component,
device, equipment, or parameter. |
| Nominal Voltage |
The stated or objective value of a given voltage, which
may not be the actual value measured. |
| Nonlinear load |
1) A load whose crest factor is greater than 1.414.
2) A load with such characteristics that with an applied sinusoidal
voltage the load current is not sinusoidal. |
| Normally closed (NQ) |
The electric contact of a device that is mechanically
shorted to the device Common (C) connection when the device is in
the deenergized mode of operation. |
| Normally Open (NO) |
The electric contact of a device that is mechanically
separated from the device Common (C) connection when the device is
in the deenergized mode of operation. |
| Null Voltage |
When the voltage between two in-phase or synchronized
sources is minimum. These sources normally are of approximately equal
amplitude so that to minimize their difference is to adjust their
phase shift to a negligible point. |
Off Line Power Supply
|
1) A power supply in which the AC line voltage is rectified
and filtered without using a line frequency isolation transformer.
2) A power supply switched into service upon line loss to provide
power to the load without significant interruption. Distinguished
from UNINTERRUPTIBLE POWER SUPPLY. |
| Ohm (Symbol: Omega) |
Unit of measure of resistance. |
| Ohm's Law |
The fundamental mathematical relationship between current
(1), voltage (E) and resistance (R) discovered by George Simon Ohm.
The passage of one Ampere through one Ohm produces one Volt. I=E/R
E=IR R=E/I (Reference the figures following) |
| On-Line Power Supply |
A power supply that continuously provides output power
to the load without any interruption. See also Uninterruptible Power
Supply. |
| Op-Amp |
Abbreviation for operational amplifier. |
| Open Loop |
A signal path without feedback. |
| Open-Circuit Voltage (OCV) |
1) The difference in potential between the terminals
of a cell or voltage when the circuit is open (no-load condition).
2) The no load voltage of a cell or battery measured with a high resistance
voltmeter. 3) The cell voltage in its stabilized idle state. The voltage
across the terminals of a cell or battery when no external current
is flowing. 4) See No Load Voltage |
| Operating Temperature |
The range of ambient, baseplate or case temperatures
through which a power supply is specified to operate safely and to
perform within specified limits. See also Ambient Temperature, Storage
Temperature. |
| Operational Amplifier (Op-Amp) |
A high gain amplifier designed to be used with external
circuit elements to provide a specific operation or function. |
| Out-of-Phase |
When comparing two AC sources, the transitions of each
phase of one source is out of step with the transition of the corresponding
phases of the second source. |
| Output |
The energy or information delivered from or through
a circuit or device. |
| Output Choke |
The inductor in the LC filter of the output. |
| Output Current |
The RMS current (unless otherwise specified for a particular
load) from the output terminals. |
| Output Current Limiting |
A protective feature that keeps the output current of
a power supply within predetermined limits during overload to prevent
damage to the supply and the load. |
| Output Filter |
One or more discrete components used to attenuate output
ripple and noise. |
| Output Filter Capacitor |
The capacitor(s) across the output terminals of a power
supply. |
| Output Impedance |
The impedance presented by the UPS output terminals
to the load. |
| Output LC Filter |
The low pass filter in the secondary of a switching
power supply that smoothes the rectified output to its average value.
Also called an averaging filter. |
| Output Power |
The power delivered by a UPS to the load. |
| Output Range |
The specified range over which the value of a stabilized
output quantity (voltage, current, or frequency) can be adjusted. |
| Output Ripple and Noise |
See Periodic And Random Deviation |
| Output Voltage |
The root-mean-square (RMS) voltage (unless otherwise
specified for a particular load) between the output terminals. |
| Overcurrent Protection |
See Output Current Limiting. |
| Overload |
When the full current or power rating of a power supply
is exceeded. |
| Overload Protection |
A feature that senses and responds to current or power
overload conditions. See also Output Current Limiting |
| Overshoot |
A transient change in output voltage in excess of specified
output regulation limits, which can occur when a power supply is turned
on or off, or when there is a step change in line or load. |
| Overvoltage |
The potential difference between the equilibrium of
an electrode and that of the electrode under an imposed polarization
current. 2) A voltage that exceeds specified limits. |
| Overvoltage Protection (OVP) |
A feature that senses and responds to a high voltage
condition. See also Overvoltage, Crowbar |
Parallel
|
1) Term used to describe the interconnection of power
sources in which like terminals are connected such that the combined
currents are delivered to a single load. The connection of components
or circuits in a shunt configuration. |
| Parallel Operation |
The connection of two or more power sources of the same
output voltage to obtain a higher output current. Special design considerations
may be required for parallel operation of power sources. |
| Peak |
Maximum value of a waveform reached during a particular
cycle or operating time. |
| Peak Inverse Voltage (PIV) |
Maximum value of voltage applied in a reverse direction. |
| Peak Inverse Voltage Rating |
The maximum rated voltage that can be applied in the
reverse direction across a semiconductor. |
| Peak Output Current |
The maximum current value delivered to a load under
specified pulsed conditions. |
| Peak-To-Peak |
The measured value of a waveform from peak in a positive
direction to peak in a negative direction. |
| Periodic and Random Deviation (PARD) |
The sum of all ripple and noise components measured
over a specified band width and stated, unless otherwise specified,
in peak-to-peak values. |
| Periodic Output Voltage Modulation |
1) The periodic variation of output voltage amplitude
at frequencies other than the fundamental output frequency. 2) The
cyclic or random dynamic variation or both of instantaneous voltage
about a mean voltage during steady state operation. |
| Phase Angle (Greek Letter THETA) |
1) The angle (usually expressed in electrical degrees)
between reference points on one or more AC wave forms. 2) The angle
that a voltage waveform leads or lags the current waveform. |
| Phase Locked Loop (PLL) |
A circuit that produces a signal with a variable frequency. |
| Phase Rotation |
The lead-lag relationship of the three phases in a 30
source. Example: A leads B leads C is Clockwise rotation and A lags
B lags C is Counterclockwise rotation. |
| Phase Shift |
The difference between corresponding points on input
and output signal waveforms (not affected by magnitude) expressed
as degrees lead or lag. |
| Phase Unbalance |
Used in reference to three phase UPS specifications
where percentage limits are placed on the phase voltage unbalance
under conditions of phase current unbalance. Load current unbalance
is computed as the worst case difference current for any two of the
three outputs divided by the average output current and times 100.
Output voltage unbalance is given by dividing the difference of the
output line voltage and the average line voltage by the average line
voltage times 100. |
| PI Filter |
A filter consisting of two line-to-line capacitors and
a series inductance in a "'pi" configuration used to attenuate
noise and ripple. |
| Pilot Cell |
A representative cell of a battery utilized to assess
the average state of the battery or a somewhat undersized cell that
is used as an indicator of the depth of discharge. |
| Plus (+) |
Positive terminal of a circuit, circuit element or power
source. |
| Polarity |
Property of device or circuit to have poles such as
north and south or positive and negative. |
| Positive Rail |
The most positive of the two output conductors of a
power supply. |
| Pot |
Abbreviation for potentiometer. |
| Power (P) |
1) The time rate of transferring or transforming energy.
2) Measured in watts, P = IE, 12 RorE2/R. One watt equals one joule/second
and one joule equals one watt-second; joule's Law mathematically describes
the heating effect of the flow of current as a result of losses, commonly,
12R losses". 3) Ina resistive circuit, power is the product of
the in-phase components voltage and current (volt-amperes). See also
Apparent Power, True Power |
| Power Factor |
The ratio of true to apparent power expressed as a decimal,
frequently specified as lead or lag of the current relative to voltage.
2) The ratio of total watts to the total root-mean-square (RMS) volt-amperes.
[Theta] is the symbol used to represent the phase angle between the
voltage and the current. |
| Power Factor Correction |
1) Technique of forcing current draw to approach being
in-phase with the voltage in an AC circuit. 2) Addition of capacitors
to an inductive circuit to offset reactance. |
| Power FET |
Specialized field effect transistor designed for high
current of high power applications. |
| Power Rating |
Power available at the output terminals of a power source
based on the manufacturers' specifications. |
| Power Source |
Any device that furnishes electrical power, including
a generator, cell, battery, power pack, power supply, solar cell,
etc. |
| Power Supply |
A device for the conversion of available power of one
set of characteristics to another set of characteristics to meet specified
requirements. Typical applications of power supplies include to convert
raw input power to a controlled or stabilized voltage and/or current
for the operation of electronic equipment. |
| Power Warning Feature (PWF) |
A feature for use primarily by IBM System 38 computers
whereby a signal is sent to the computer to warn of a utility power
outage, giving the computer an opportunity to finish jobs in process
before an organized shut-down, with an IBM user programmable delay
based upon battery back-up time. |
| Primary Winding |
A driven coil in a transformer. |
| Prime Power |
The power normally continuously available which is usually
supplied by electrical utility company but sometimes by the user's
own generation. |
| Pulsating Direct Current |
DC voltage containing an AC voltage ripple component. |
| Pulsating Load |
A load current waveform having sudden changes of brief
duration imposed upon it (where the average current is not zero). |
| Pulse |
A step rise, a level, and a step fall of voltage or
current. Characteristics of a pulse are: rise time, duration and fall
time. |
| Pulse-Width Modulation (PWM) |
A method of regulating the output voltage of a switching
power supply by varying the duration, but not the frequency or amplitude,
of a train of pulses that drives a power switch. |
| Pulse-Width Modulator (PWM) |
An integrated 0 =L 25% discrete circuit used in switching-type
power OFF DUTY CYCLE supplies, to control the conduction time of pulses
produced by the clock. |
| PWM |
Variously, the abbreviation for pulse |
Ramp Generator
|
An electronic circuit which has linearly increasing
or decreasing output voltage during periodically repeating time intervals. |
| Rated Capacity |
1) The number of ampere-hours a cell or battery can
deliver under specific conditions (rate of discharge, end voltage,
temperature); usually the manufacturer's rating. 2) The average capacity
delivered by a cell or battery on a specified load and temperature
to a voltage cutoff point, as designated by the manufacturer; usually
an accelerated test approximating the cell or batteries capacity in
typical use. |
| Rated Output Current |
The maximum continuous load current a power supply is
designed to provide under specified operating conditions. |
| Rating |
The whole of the electrical and mechanical quantities
assigned to the machine, apparatus, etc. by the designer to, define
its working in specified conditions indicated in the rating nameplate. |
| Reactance M |
Opposition to alternating current as result of inductance
or capacitance. |
| Reactive |
A component that exhibits the property of either capacitance
or inductance. |
| Recovery Time |
The time interval between a change in a parameter and
when the stabilized value of the parameter returns to and stays within
the steady state tolerance. |
| Rectification |
The process of changing an alternating current to a
unidirectional current. See Full-Wave Rectifier, Half-Wave Rectifier |
| Rectifier |
1) A device or assembly of devices that converts AC
power into DC power to supply the input power to an inverter but not
a battery. 2) A component that passes current only in one direction,
e.g., a diode. |
| Rectifier Type UPS System |
A UPS employing both an unregulated rectifier to supply
DC power to the inverter, but also a trickle-charge battery charger
of insufficient size to power the inverter but solely keeping the
batteries fully charged. |
| Redundancy |
The existence of more than one means for performing
a given function. |
| Reference Ground |
Defined point in a circuit or system from which potential
measurements shall be made. |
| Reference Voltage |
The defined or specified voltage to which other voltages
are compared. |
| Regenerative |
In a device whose information storage may deteriorate,
the process of restoring or refreshing to the non-deteriorated condition.
Regenerative feedback is a sample of the output being returned to
the input. |
| Regulated Power Supply |
A device that maintains within specified limits a constant
output voltage or current for specified changes in line, load, temperature
or time. |
| Regulated Rectifier |
A rectifier employing phase controlling or other type
of voltage regulating circuitry to supply DC output voltage regulation
to a much tighter percentage than the tolerance of the AC input voltage. |
| Regulating Transformer |
A transformer capable of controlling its output voltage
within specified limits by compensating for variations in input voltage
and load. |
| Regulation |
The process of holding constant selected parameters,
the extent of which is expressed as a percent. |
| Relay |
A magnetic component or Solidstate device that opens
or closes an isolated switch(es) when a voltage Is applied to the
control terminals. |
| Remote Sensing |
A technique for regulating the output voltage of a power
supply at the load by connecting the regulator error-sensing leads
directly to the load. Remote sensing compensates for specified maximum
voltage drops in the load leads. Care should be exercised to avoid
opening load handling leads to avoid damaging the power supply. Polarity
must be observed when connecting sense leads to avoid damaging the
system. |
| Reset Signal |
A signal used to return a circuit to a desired state. |
| Resistance () |
Property of a material that opposes the flow of current. |
| Resonance |
1) The state in which the natural response frequency
of a circuit coincides with the frequency of an applied signal, or
vice versa, yielding intensified response. 2) The state in which the
natural vibration frequency of a body coincides with an applied vibration
force, or vice versa, yielding reinforced vibration of the body. |
| Resonant Circuit |
A circuit in which inductive and capacitive elements
are in resonance at an operating frequency. |
| Resonant Frequency |
The natural frequency at which a circuit oscillates
or a device vibrates. In an L-C circuit, inductive and capacitive
reactances are equal at the resonant frequency. |
| Response Time |
The time required for the output of a power supply or
circuit to reach a specified tolerance after a step change or disturbance. |
| Restored Energy Time |
The time required by the energy storage means of the
UPS to be charged to provide a second rated stored energy time after
providing rated stored energy time. |
| Return |
The name for the common terminal of the output of a
power supply; it carries the return current for the outputs. |
| Reverse Polarity |
A connection that is opposite to that which is specified
or intended. |
| RFI |
Abbreviation for Radio Frequency Interference. |
| Ride-Through |
The time interval that load will be powered by an output
after the input has ceased, i.e. the time the ferroresonant or output
transformer will carry load once the inverter bridge has stopped operating
(largely dependent on the size of the output filter arrangement. |
| Ringing Peak |
In a forced-com mutated inverter circuit, the SCR's
are forced to resume a blocking state by the discharge of a commutating
capacitor causing the collapse of a large magnetic field which developed
in the commutating choke. The capacitor is recharged to an extent
by the decaying field, and again discharges into the choke, causing
a ringing to occur. The first peak of this ringing is significant
because it is the highest voltage peak, and may not exceed the rating
of the bridge semiconductors. |
| Ripple |
The periodic AC component at the power source output
harmonically related to source or switching frequencies. Unless specified
otherwise, it is expressed in peak-to-peak units over a specified
band width. |
| Ripple and Noise |
See Periodic And Random Deviation (PARD) |
| Ripple Voltage |
The periodic AC component of the DC output of a power
supply. |
| Rise Time |
The time required for a pulse to rise from 10 percent
to 90 percent of its maximum amplitude. |
| RMS |
Abbreviation for root mean square value. In text, use
lower case: rms. |
| Root Mean Square Value (RMS) |
For a sine wave, .707 x E PEAK' |
Safety Ground
|
A conductive path from a chassis, panel or case to earth
to help prevent injury or damage to personnel and equipment. |
| Sag |
Momentary decrease in line voltage usually caused by
in-rush loads. |
| Reactor |
A magnetic component with a square loop hysteresis curve.
The saturable reactor when driven in and out of saturation functions
as a magnetic amplifier or switch. |
| Saturation (Magnetic) |
A condition in a magnetic material in which an increase
in flus density (B) will no longer produce an appreciable increase
in field intensity (H). |
| Scott 'IT" |
Transformer connection whereas 30 voltages are developed
by using only two transformers. |
| SCR |
Abbreviation for SILICON CONTROLLED RECTIFIER |
| Sealed Cell |
A cell which is sealed under normal conditions, but
allows the escape of gas if the internal pressure exceeds a critical
value. |
| Secondary |
A cell or battery designed to be recharged. See also,
Secondary Output, Secondary Winding |
| Secondary Winding |
A coil that receives energy from the primary winding
by mutual induction and delivers energy to the load is the secondary
winding. |
| Self Protective Action |
Any equipment alarm function employing a control function
such as partial shut-down or transfer, in order to prevent damage
to its circuit. |
| Sequencing |
The process that forces the order of turn on and turn
off of individual outputs of a multiple output power supply. |
| Series |
1) The interconnection of two or more power sources
such that alternate polarity terminals are connected so their voltages
sum at a load. 2) The connection of circuit components end to end
to form a single current path. |
| Series-Parallel |
A circuit having a combination of series and parallel
components. |
| Service Life |
The period of useful life of a primary cell or battery
before a predetermined end-point voltage is reached. 2) Period of
useful life of a power supply before a predetermined end of life point
is reached. Service life may be significantly increased by the replacement
of select components. |
| Shelf Life |
The duration of storage under specified conditions at
the end of which a component or device retains the ability to give
a specified performance. |
| Short-Circuit |
A direct connection that provides a virtually zero resistance
path for current. |
| Short-Circuit Current (SCQ) |
1) The initial value of the current obtained from a
power source in a circuit of negligible resistance. 2) The current
which flows from the UPS into zero impedance load. |
| Short-Circuit Protection |
A protective feature that limits the output current
of a power supply to prevent damage. |
| Shunt |
1) A parallel conducting path in a circuit. 2) A low
value precision resistor used to monitor current. See Magnetic Shunt. |
| Shunt Trip |
An accessory device attached to a circuit breaker to
enable control circuitry to remotely trip the breaker. |
| SI |
The Standard International system of units. |
| Signal Ground |
The common return or reference point for analog or digital
signals. |
| Silicon-Controlled Rectifier |
A unit-directional, four-layer (PNPN) junction device
in which conduction is initiated by the application of a gate current.
Conduction will continue until the current is reduced to some minimum
value. |
| Sine Wave |
A wave form of a single frequency alternating current
whose displacement is the sine of an angle proportional to time or
distance. Also see Sinosoidal. |
| Single Phase |
A two or three wire AC source which has 1800 vector
displacement between its output leads. |
| Single Point Ground |
The one point in a system that connects multiple grounds
and returns. Also known as star ground or holy point ground. |
| Sinusoidal |
The waveform derived by rotating a vector counterclockwise
at a linear rate (frequency) and plotting the sine function of its
angular displacement. |
| Slave |
A power supply which uses the reference in another power
supply, the master, as its reference. |
| Slew Rate |
The change in frequency of a periodic waveform from
one period to the immediately subsequent period divided by the average
of the two periods. |
| Snubber |
An RC network used to reduce the rate of rise of voltage
in switching applications. |
| Snubber Network |
A circuit that uses a RC network and a diode in unipolar
switching applications. |
| Soft Starts |
Controlled (ramped) turn on to reduce inrush currents. |
| Solidstate Relay |
A completely electronic switching device with no moving
parts or contacts. |
| Solidstate Switch |
A switch that uses no moving parts. Also see Static
Switch. |
| Source |
Origin of the input power, e.g., generator, utility
lines, mains, batteries, etc. |
| Specific Gravity |
The specific gravity of a solution is the ratio of the
weight of the solution to the weight of an equal volume of water at
a specified temperature. |
| Spike |
A short duration, high frequency overvoltage transition. |
| Square Wave |
1) In digital circuits, a waveform characterized by
only two voltage levels, very fast transitions from one level to the
other, and equal periods of time at each level. 2) The inverter bridge
waveform in ferroresonant inverters. 3) By waveform analysis, the
sum of a fundamental frequency sine wave with all of its odd harmonics. |
| Standby Power |
The power intended to replace prime power in case of
prime power failure. See Alternate Source. |
| Start-up Delay |
The time delay between either applying power or a remote
"on" and the time at which the outputs are in regulation. |
| Start-up Sequence |
The order of events that occur in a power supply during
start up. |
| Static Converter |
A unit that employs static switching devices, such as
controlled rectifiers, transistors, or magnetic amplifiers. |
| Static (Transfer) Switch |
A Solidstate switch used in Standby Power Supply (SPS)
and Uninterruptible Power Supply (UPS) systems for transferring the
load between the primary AC power and secondary AC power. |
| Static Load |
A load that remains constant over a given time period. |
| Stationary Battery |
A secondary battery designed for use in a fixed location. |
| Status Signals |
Logic signals that indicate normal or abnormal conditions
of operation, including AC low, AC ok, over temperature, under temperature,
DC low, DC ok, overvoltage, overcurrent. |
| Steadystate |
The condition in which some value, such as amplitude
periodicity or rate of change, exhibits negligible change over an
arbitrary long interval of time. |
| Step-Down Transformer |
A transformer with a turns ratio more than one. The
output voltage is less than the input voltage. See also, Isolation
Transformer, Step-Up Transformer, Transformer |
| Step-Up Transformer |
A transformer with a turns ratio less than one. The
output voltage is greater than the input voltage. Se also, ISOLATION
TRANSFORMER, STEP-DOWN TRANSFORMER, TRANSFORMER |
| Step Change |
An abrupt and sustained change in one of the influence
or control quantities of a power supply. |
| Step Load Change |
The instantaneous addition or removal of electrical
loads to a power source. |
| Storage Battery |
A galvanic battery which once discharged may be recharged
by passing a direct current through the cell in the opposite direction
to the discharge current, designed for use in a fixed location. |
| Storage Temperature |
A range of ambient temperature through which an inoperative
power supply can remain in storage without degrading its subsequent
operation. See Ambient Temperature, Operating Temperature. |
| Stored Energy Time |
The minimum time that the UPS will provide continuity
of load power (under specified service conditions starting with a
fully charged energy storage means) in the absence of AC input power. |
| Surge |
A sudden, strong overvoltage transition. |
| Surge Arrester |
A protective device for limiting surge voltages on equipment
by discharging or bypassing surge current; it prevents continued flow
of follow current to ground, and is capable of repeating these functions
as specified. |
| Symmetrical |
A current or voltage waveform having the same magnitude
above & below the zero, axis. |
| Sync |
Abbreviation for synchronize. |
| Sync Null |
See Nuli Voltage. |
| Synchronization |
The act of being synchronized. |
| Synchronous (Synchronized) |
1) The transitions of the Commercial AC Power waveform
(sine wave) are in step with the transitions of the AC Power waveform
from the Battery/inverter of the UPS. 2) The state where AC systems
operate at the same frequency and where the phase-angle displacements
between voltages are constant. |
| Synchronous |
When two sources are operating with their voltage transitions
in step. |
Takeover voltage
|
A voltage source developed from the inverter bridge
square wave.It is used to power the osciIlator and static switch control
boards at al I times except during the starting of the inverter. |
| Tap-Changer |
A line voltage regulating equipment employing a multiple
winding transformer where voltage regulation is achieved by controls
selecting the appropriate transformer taps. Also see Regulating Transformer. |
| Temperature Coefficient |
The average percent change in output voltage per degree
Centigrade change in ambient temperature over a specified temperature
range. See also Ambient Temperature. |
| Termination |
The hardware used to make the electrical input, output,
and feed through connections. |
| Thermal Runaway |
1) A condition whereby a cell or battery on charge or
discharge will destroy itself through internal heat generation caused
by high overcharge or over discharge current or another abusive condition.
2) The critical condition arising during constant potential charging,
in which charging current and electrolyte temperature produce a commutative
self-reinforcing effect to further increase current and electrolyte
temperature. 3) A condition in which a cell or battery on constant-potential
charge can destroy itself through internal heat generation. 4) A condition
in a power source or component where an increase in temperature increases
current flow causing a further increase in temperature, the spiraling
effect of which leads to failure. |
| Three Phase |
A three or four wire AC source which usually has 1200
vectoral displacement between three of its leads and if there is a
fourth wire, 180' displacement between each of the three leads to
this common fourth lead. |
| Three Wire Output |
A single, two or three phase AC source with three output
leads. |
| Three-Phase |
Three electromotive forces (voltages) that differ in
phase by 1/3 of a cycle, that is 1200. Voltage levels are usually
the same. |
| Thyristor |
A Solidstate device that has bistable electrical characteristics.
Three common thyristor devices are diacs, silicon controlled rectifiers
(SCR's) and triacs. |
| Time Constant (RC) |
Time period required for the voltage of a capacitor
in an RC circuit to increase to 63.2 percent of maximum value or decrease
to 36.7 percent of maximum value. |
| Tolerance |
The total permissible variation of a quantity from a
designated value. |
| Total Harmonic Distortion (THD) |
The ratio of the root-mean-square (RMS) value of all
the harmonics to the root-mean-square (RMS) value of the fundamental
usually expressed in percent. |
| Total Regulation Bank |
The range of combined regulation tolerances such as
the effects of input voltage variation, output load variation, temperature
variation, drift and other specified variables. It is expressed as
a plus/minus percent from nominal. Also called accuracy limits. |
| Transfer |
To switch the output between two or more sources of
prime power. In the UPS, the sources are Commercial AC Power and the
Battery (AC output power from the Battery via the Inverter). |
| Transfer Switch |
A switch used to transfer a load from one power source
to another. |
| Transformer |
Device which transfers energy from one circuit to another
by electromagnetic induction. See Isolation Transformer, Step-Down
Transformer, Step-Up Transformer |
| Transient |
An excursion in a given parameter, typically associated
with input voltage or output loading. That part of the variation which
ultimately disappears in a quantity during transition from one steady-state
operating condition to another. |
| Transient Effect |
The result of a step change in an influence quantity
on the steady state values of a circuit. |
| Transient Recovery Time |
The time required for the output voltage of a power
supply to settle within specified output accuracy limits following
a transient. |
| Transient Response |
Response of a circuit to a sudden change in an input
or output quantity. |
| Transient Response Time |
The interval between the time a transient is introduced
and the time it returns and remains within a specified amplitude range. |
| Transient Voltage |
Transient voltage is generated when loads energize and
deenergize, particularly inductive loads. UPS systems serve to isolate
critical loads from the negative results of such transients, such
as the peak voltage, the rate of rise of the transient, DV/DT, and
the duration of the transient. |
| Triac |
A bi-directional silicon-controlled switch. |
| Trickle Charge |
1) A charge at low rate, balancing losses through local
action and/or periodic discharge, to maintain a cell or battery in
a fully charged condition. 2) A method of recharging in which a secondary
cell is either continuously or intermittently connected to a constant-current
supply that maintains the cell in a fully or near fully charged condition.
3) The method of long time keeping a charged battery in fully charged
state by applying a low constant charge current. 4) A method of maintaining
the capacity of the cell by applying a small, constant current to
the cell. |
| Trip Curve |
Similar to time-current characteristic curve for fuses
except that circuit breakers will often indicate more than one specific
region of operation due to the additional features of magnetic trip
and thermal trip. |
| True Power |
Actual power generated or consumed in a circuit. |
| True RMS Meter |
A meter that measures the RMS voltage rather than average
or some other value. |
| Tuned Circuit |
Circuit containing capacitance, inductance and (optionally)
resistance, connected in series or parallel, which when energized
at a specific frequency known as its resonant frequency, an interchange
of energy occurs between the coil and the capacitor. |
| Turn-off Time |
The length of time that an SCR must be reverse biased
to guarantee its turn off. |
| Turns Ratio |
Ratio of the number of turns on the primary winding
of a transformer to the number of turns on the secondary winding. |
| Two Phase |
A two wire or three wire AC source which exists between
two of the leads; vectoral displacement other than 180*. |
| Two Wire Output |
A single or two phase AC source which uses two output
leads. |
Undervoltage Protection
|
A circuit that inhibits the power supply when output
voltage falls below a specified minimum, and that sometimes has an
audible/visual alarm. |
| Uninterruptible Power Supply System (UPS) |
A system that converts unregulated input power to voltage
and frequency controlled filtered AC power that continues without
interruption even with the deterioration of the input AC power. It
is commonly referred to as UPS. See also Off Line Power Supply, On
Line Power Supply. |
| Unregulated Rectifier |
A device that receives an unregulated AC voltage and
rectifies but does not regulate it. |
| UPS Switch |
A switch (electronic or mechanical, depending on required
continuity of power) used to connect, interrupt, isolate, or transfer
power flow within a UPS. |
| Utility Power |
The commercially available AC feed power from the utility
company. |
| Variation |
The change in the value of a quantity from its mean
or typical value. |
| Vital Loads |
Vital instrumentation and control power systems identified
in ANSIAEEE Std. 3081980 or other loads as specified that are important
to plant operation or personnel safety, or both. |
| Volt |
Unit of measurement of electromotive force or potential
difference. Symbol E, in electricity; symbol V in semiconductor circuits. |
| Volt-Ampere |
Measurement unit of apparent power. |
| Voltage |
A derivative electrical quantity, E, measured in the
unit Volts and defined in terms of the independently obtained Ampere,
1, and the unit of resistance, Ohm (R) by Ohms Law E = IR. |
| Voltage Divider |
Tapped or series resistance or impedance across a source
voltage to produce multiple voltage. |
| Voltage Drop |
Difference in potential between two points in a passive
component or circuit. |
| Voltage Imbalance Factor |
The ratio of the amplitudes of the negative-sequence
component to the positive-sequence component of the line-to-line output
voltage. |
| Voltage Limit |
Maximum or minimum value in a voltage range. |
| Voltage Monitor |
A circuit or device that determines whether or not an
output voltage is within some specified limits. |
| Voltage Regulation |
1) The process of holding voltage constant between selected
parameters, the extent of which is expressed as a percent. 2) The
relative percent change of voltage during (cell/ .battery) discharge.
See also Regulation |
| Voltage Regulator |
A device that controls output voltage within a specific
range when the input voltage and connected load are within specified
ranges. |
| Voltage Source |
A power source that tends to deliver constant voltage. |
Walk-in
|
A controlled power increase by the UPS from the AC input
into the UPS. |
| Warm-up Time |
The time required after a power supply is initially
turned on before it operates according to specified performance limits. |
| Warm-up |
Process of approaching thermal equilibrium after turn
on. |
| Warm-up Drift |
The change in output voltage current or frequency of
a power source from turn on until it reaches thermal equilibrium at
specified operating conditions. |
| Wave |
Any form of disturbance that exhibits a periodic (repeating)
pattern. |
| Waveform |
A representation or expression used to describe the
shape of a wave disturbance as observed on a display instrument. |
| Waft |
Unit of measurement of power equal to 1 joule/sec. (W=EI) |
| Watt-Hour |
Unit of energy measurement, equal to one watt per hour
(3600 joules). |
| Winding |
A conductor wrapped onto a magnetic core or core for,
e.g., a transformer primary or secondary. |
| Worst Case Condition |
A set of conditions where the combined influences on
a system or device are most detrimental. |
| Wye Connection |
In a three-phase alternating-current system, a wye connection
is a method of interconnection the windings of a transformer to a
common point. The configuration gets its name from the fact that,
in a schematic diagram, it appears like a capital letter Y. |
| Yearly Average Temperature L |
The time average of bulk air temperature taken over
a period of one year. |
| Zener Diode |
A diode that makes use of the breakdown properties of
a PN junction. If a reverse voltage across the diode is progressively
increased, a point will be reached when the current will greatly increase
beyond its normal cut-off value to maintain a relatively constant
voltage. Either voltage point is called the Zener voltage. The breakdown
maybe either the lower voltage Zener effect or the higher voltage
avalanche effect. |
| Zener Voltage |
The reverse voltage at which breakdown occurs in a zener
diode. |
| Zero Break |
Transfer -A transfer between two sources whereas no
loss of continuity or interruption occurs to the output. |
| Zig-Zag Transformer Configuration |
The connection in star of polyphase windings, each branch
of which is made up of windings that generate phase-displaced voltage. |
