| 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 (unpowered)
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 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 noninverting
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 Rms 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 osciIlator 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. deenergized, magnetized vs. demagnetized, 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 nonautomatic
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 elementsconnected 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 ransfera
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 resuIt 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 |
A 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 nonvarying 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: Atypeof 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 coulwb 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 all the 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. |
| FloatCharge |
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 Iines of magnetic force. |
| Flux Density (B) |
Number of Iines of flux per cross-sectional area of a magnetic circuit
in Gauss. |
| Foldback Current Limiting |
Apower 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 receives 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 preadjusted 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 aperiodic 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 LetterTHETA) |
1) The angle (usually expressed in electricaI 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 undeteriorated 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 |
