AC - Alternating current. Current flows first in one direction, then reverses and flows the opposite direction, typically in a sinusoidal fashion. The number of times this change takes place per second is called frequency.
Agent - See SNMP Agent.
Alarm Enable/Disable - The switch used to disable the Audible Alarm feature. It does not affect the Visual Alarm indicators.
Ambient temperature - The range of air temperature on a normal basis surrounding the equipment.
Ampacity - The current carrying capacity, expressed in amperes, of a conductor under stated thermal conditions.
Ampere (Amp or A) - The mks unit of measure for current flow in electrical conductors or devices. May be AC or DC Amps. One ampere equals one coulomb passing a point in a conductor in one second. Or the unit of measurement of electrical current produced in a circuit by 1 volt acting through a resistance of 1 ohm.
ANSI - American National Standards Institute. An industry group that establishes and publishes standards.
Apparent Power - Volt-Amperes, VA. The product of voltage times current in a circuit including inductive and/or capacitive elements.
Arrester - A device to suppress voltage spikes, sometimes called suppressor or protector. (See Suppressor.)
Audible Alarm - The horn that sounds when an alarm condition occurs.
Audible Noise - The measure of the noise emanating from equipment in audible frequencies. Usually represented in dBA.
Autoranging Input - Refers to ETI products being able to automatically select input voltage. For example, the autoranging can select either 115 or 230-vac input, providing an input range of 85 to 270 vac having either a 50 or 60 Hz frequency. This covers 99+% of the world.
Autotransformer - A transformer used to step voltage up or down. The primary and secondary windings share common turns, and it provides no isolation.
AWG - American Wire Gauge. A gauging system used to size wire. Every increase of 3 wire gauges is a 50% reduction in cross sectional area of the wire.
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Bandwidth - A term now used to describe the capacity or amount of traffic (data, voice or video) a certain communications medium is capable of accommodating.
Battery - An electro-chemical device that is used to store chemical energy and convert it to produce electrical power. Basic technologies used with UPS products include lead-acid and nickel-cadmium (NICAD).
Battery Backup - A battery or a set of batteries in a UPS system. Its purpose is to provide an alternate source of power if the main source is interrupted.
Battery Charger - An electronic device that provides a controlled voltage and current to a battery to maintain the battery in a fully charged state.
Battery Charger Modes - A Constant Current Rate of Charge Mode is used until the battery is just below float level. Once the batteries have reached this point, the charging mode changes to a Constant Voltage Mode (Trickle Charge Mode) that is used to maintain the float level of the batteries.
Battery Self Discharge - The internal current flowing in a battery when it is not connected to a circuit. The rate of self-discharge is proportional to the storage temperature, thus batteries have a longer self-life at lower temperatures.
BEM - Battery Extension Module. A specific group of batteries in a self contained enclosure with circuit protection and interface connector.
Bi-Directional Converter - A device that changes (or converts) alternating-current power to direct-current power and vice versa.
Blackout - A total loss of the AC utility (commercial power). A zero-voltage condition that lasts for more than two cycles. It may be caused by the tripping of a circuit breaker, power distribution failure or utility power failure. This condition can lead to data damage, data loss, file corruption and hardware damage.
Brownout - A low voltage situation. Some equipment will not work in a brownout, whereas others will, depending on the severity. In either case, a brownout is bad for electrical equipment.
Many authorities consider a brownout of 80% or less of normal voltage levels to be a Blackout. (See Under voltage.)
Boost - See buck and boost.
Break-Before-Make - Operational sequence of a switch or relay where the existing connection is opened prior to making the new connection.
Breaker - See Circuit Breaker.
Bridge Converter - Switching converter topology that employs four switching elements (full bridge) or two switching elements (half-bridge). This topology is more often used in off-line supplies rather than DC-DC converters. Bridge converters provide high output power and low ripple, but are significantly more complex than other types of converter topologies and thus are more expensive and prone to failure. Also see Boost Regulator, Buck Regulator, Flyback Converter, Forward Converter, Push-Pull Converter and Resonant Converter.
Brownout - The term used to describe when the power grid voltage is something less than the normally accepted tolerance, but voltage is still present. Power companies sometime lower voltage during power shortages to reduce load on several customers rather than completely dump customers. It occurs more often as an uncontrolled condition during high peak demand. Each piece of electronic equipment has a low voltage limit it can tolerate. When this happens, computer systems can experience data corruption, data loss and premature hardware failure.
BTU - British Thermal Unit. The quantity of heat required to raise the temperature of 1 pound of water by 1 °F starting from 60 °F. This is equal to 1054.6 joules or 252 calories. 3.7 BTU's per hour is equivalent to 1 Watt.
Buck and Boost - A proprietary voltage regulation process used when an over voltage or under voltage situation occurs in the UPS. Under voltage is boosted to make the voltage greater, and over voltage is bucked to reduce it. The result is less reliance on the UPS battery, extending overall battery life.
Buck Regulator - A basic DC-DC switching converter topology that takes an unregulated input voltage and produces a lower regulated output voltage. The lower output voltage is achieved by chopping the input voltage with a series connected switch (transistor) that applies pulses to an averaging inductor and capacitor.
Burn In - The process of operating newly manufactured equipment for some period of time prior to shipment. The intent is to stabilize the electronics and eliminate infant mortality by aging the device. The time period and conditions (input power cycling, load switching, temperature, etc.) varies from vendor to vendor.
Bypass - A circuit used to change the path of the electrical power so that it goes around (or bypasses) its normal path. In the UPS, the bypass circuit is used to route the power around the major electronics in the UPS so they can be serviced without power interruption.
Calorie - A unit of heat. One calorie is the amount of energy required to raise the temperature of one gram of water by one degree of Celsius.
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Capacitor - A device that stores electrostatic energy in a manner similar to the way an inductor stores electromagnetic energy. Often used for filtering or DC blocking. The unit of capacitance is the Farad (F).
CBEMA - Computer and Business Equipment Manufacturers Association. Organization originally responsible for the AC voltage disturbance tolerance specification used by related equipment designers. Specifies over voltage and under voltage events that computing equipment must withstand. Effective December 1994, CBEMA changed its name to the Information Technology Industries Council (ITI).
CE - European Union regulatory community symbol. Symbolizes compliance with all applicable safety, public health and consumer protection requirements. See UL, CSA, ETL, VDE and TÜV.
Celsius (°C) - A metric measure of temperature level, degrees Celsius.
CFM - Cubic feet per minute, which is a measure of the volume of air flowing in a system.
Choke - An inductor used as part of an electrical filter that resists the flow of current at specified frequencies, usually used to block high-frequency transients from incoming a/c power. See Inductor.
Circuit Breaker (CB) - A re-settable over current protective device that operates (trips) after a certain current level is exceeded for a certain length of time. Common designs include thermal, magnetic and combinations of both.
Clean Power - Electrical power that has been conditioned and/or regulated to remove electrical noise from the output power. An ideal sine wave does not contain distortion, ripples, spikes, distortions, or phase shifts.
Cold Start - The ability to start the UPS from its batteries without having the Input AC present.
Common Mode (CM) - The term refers to electrical interference, which is measurable as a ground referenced signal. In true common mode, a signal is common to both the current carrying conductors.
Common Mode Noise Rejection (CMNR) - The ability of an electronic device, like a UPS, to block common mode noise between input and output.
Conduit - A flexible or rigid tubular raceway for data or power cables. Metallic conduit is common, although non-metallic forms may also be used.
CONUS - Continental United States. Typically refers to an electronic device designed to operate from standard US power, 120 vac, 60 Hz.
Converter - An electronic device that takes on level of DC power and converts it to another level, up or down (DC/DC). A device which changes electrical energy from one form to another, such as from alternating current to direct current.
Coulomb - The combined negative electrical charge of 6.24 X 1018 electrons.
CPC - Circular Plastic Connector. A type of modular connector by AMP that is less expensive than the metal shell connectors.
Crest Factor - The ratio of the non-linear peak current to the true RMS current. A sine wave has a crest value of 1.4142. For switch model power supplies this ratio ranges from 2 to 4.
Critical Load - Equipment that requires an uninterrupted power input to prevent damage or injury to personnel, facilities, or itself.
Crowbar - A circuit that crowbars or rapidly shuts down a converter's output if a preset voltage level is exceeded. The circuit places a low resistance shunt across the output when an over voltage condition exists.
CSA - Canadian Standards Association, a Canadian safety agency that sets standards for product safety. See UL, ETL, CE, VDE and TÜV.
Current - The measure of electrical charge passing a particular point. Commonly measured in Amperes. See Ampere.
Current limiting - Feature that protects the electrical equipment from damage under overload conditions such as a short circuit. The maximum output current is automatically limited to a predetermined safe value. If the equipment is specified for auto restart, normal operation is automatically restored when overload condition is removed.
Current rating - The maximum current which a piece of electrical equipment was designed to carry or produce.
Current Transformer (CT) - Usually used as a sensing device, current transformers customarily have a one turn primary. The number of secondary turns is determined by the sensitivity required and is terminated with a resistor. Toroidal in shape, cores of silicon steel, nickel alloy, or ferrite are used. Choice of core material influences cost and accuracy.
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Db - Decibel. A unit used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm of the ratio of the two levels. Decibels indicate the ratio of power output to power input dB = 10 log10 (P1/P2).
DC - Direct Current. Electrical current that flows in one direction only. Or also a type of electrical current that is always on the same side of the reference point (like positive, compared to 0, or negative compared to 0).
DC-DC Converter - A circuit or device that converts a DC input voltage (usually unregulated) to a regulated DC output voltage. The output voltage may be lower, higher, or the same as the input voltage. Switching regulator DC-
DC circuits most often require an inductor or transformer to achieve the regulated output voltage. Switching regulator circuits can achieve a higher level of power efficiency when compared to non-switching techniques.
Delta Connection - A standard three phase connection with the ends of each phase winding connection in series to form a closed loop with each phase 120 electrical degrees from the other. In this system, three power carrying conductors are used, sometimes with a fourth safety ground wire.
Delta-Delta - The connection between a delta source and a delta load.
Delta-Wye - The connection between a delta source and a wye load.
Derating - Utilizing a component or piece of equipment intentionally below its specified rating to allow for variations in operating parameters such as temperature.
Dip - A short brownout, often caused by motors turning on and off, such as on large air conditioners.
Double Conversion - A UPS design in which the primary power path consists of a rectifier and inverter. Double conversion isolates the output power from all input anomalies such as low voltage, surges and frequency variations by converting AC to DC to AC. See Online UPS.
Dropout Voltage - The voltage at which a device fails to operate properly or safely. Computer systems will reboot, reset, or lose data when line voltage falls below approximately 95-100 Volts AC. See Brownout.
Dual Source Input - In this case, the UPS has both a primary and secondary source feeding it. If either source fails, the other takes over with no break. If they both fail, the batteries take over with no break.
Dry Contact - Isolated contacts through which the end user supplies an external circuit. UPS dry contacts provide basic communication capabilities such as monitoring and shutdown.
Dynamic regulation - The ability to hold the controlled level to specification while other parameters vary, i.e. dynamic voltage regulation while the load is changing.
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Earth ground - A low impedance path to earth for the purpose of discharging lightning, static, and radiated energy, and to maintain the main service entrance at earth potential.
Efficiency - The ratio of the output power from the UPS to the input power from the utility. The mathematical formula is: Efficiency = Po/ Pi Where "Po" equals power output, "Pi" equals power input, and power is represented by watts. This shows the percentage of the input power that is available as useful output power. For example, a UPS that is 85% efficient delivers 85% of the utility power it receives to the load. The remaining power takes the form of dissipated heat.
EIA - Electronic Industries Alliance. An organization that helps set standards in the electronics industry.
Electrician - Refers to an installation electrician qualified to install heavy-duty electrical components in accordance with local codes and regulations. May not qualified to maintain or repair electrical equipment; compare to Technician.
Electromagnetic - A magnetic field caused by an electric current. Power lines cause electromagnetic fields that can interfere with nearby data cables.
Electromechanical - A mechanical device, which is controlled by an electric device. Solenoids and shunt trip circuit breakers are examples of electromechanical devices.
Electrostatic - A potential difference (electric charge) measurable between two points, which is caused by the distribution if dissimilar static charge along the points. The voltage level is usually in kilovolts.
Electrostatic Discharge (ESD) - Current produced by two objects having a static charge when they are brought close enough to produce an arc or discharge (static electricity). The effects of static discharge can range from simple skin irritation for an individual to degraded or destroyed semiconductor junctions for an electronic device.
Electrostatic Shield - A metallic barrier or shield between the primary and secondary windings of a transformer, which reduces the capacitive coupling and thereby increases the transformers ability to reduce high frequency noise. See Faraday Shield.
EMF - Electromotive force or voltage. See Voltage.
EMC - Electro Magnetic Compatibility. The requirement for both electromagnetic emissions and susceptibility of a piece of equipment to comply with a governing set of standards.
Emergency Shutdown - Used to instantly or quickly shutdown all of the electrical power available to the UPS, the power supply and/or the load. An emergency shutdown device is usually used during a crisis to prevent damage to the UPS and the load. The local control switch or switches are commonly referred to as the EPO or Emergency Power Off. Some installations require a Remote Emergency Power Off (REPO) capability as part of their security/safety system.
|EMI/RFI - Electro Magnetic Interference and Radio Frequency Interference. Caused by inter-alia, such as lightning, generators, radio transmitters, and industrial equipment.
Electrical energy emitted by one electrical device that may disturb the normal operation of another device. The interference is either radiated emissions (RE) from the surface of a device or conducted emissions (CE) via its hard-wired electrical connections.
EMI/RFI Filter - A device that suppresses or reduces the level of EMI/RFI emitted by electrical or electronic equipment.
EPO - Emergency Power Off. See Emergency Shutdown.
Ethernet - A base-band LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Often referred to as a contention-based topology because workstations are in competition for channel bandwidth. For this reason, Ethernet uses a cable-sharing process called Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Ethernet has become a series of standards produced by IEEE referred to as IEEE 802.3.
ETL - Electrical Testing Laboratories. A US independent safety agency that sets standards for product safety. See UL, CSA, CE, VDE and TÜV.
ETM - Elapsed Time Meter. A time measurement device that is counting time only when a piece of equipment is energized. Typically used to log total operational hours of the equipment for maintenance and event logging.
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Fahrenheit (°F) - An English measure of temperature level, degrees Fahrenheit.
Farad (F) - Unit of measurement for capacitance.
Faraday Shield - A grounded electrostatic shield that reduces coupling capacitance in transformers. The shield, which effectively reduces output common mode noise, is placed between the primary and secondary windings of a transformer.
Fault Current - The level of current that can flow if a short circuit is applied to a voltage source.
Fault Tolerance - The ability of a system to continue operating in the event of a fault.
FCC - Federal Communications Commission. The FCC specifies the maximum amounts of EMI and RFI that electrical equipment is permitted to generate in Part 15 of the FCC Rules and Regulations.
Ferro-resonant Transformer - Transformer in which part of the core is driven into saturation by a resonant tank circuit. The output of the transformer, taken from the saturated portion, is relatively immune to variations in input voltage.
Filter - An electronic device that blocks certain frequencies while allowing other frequencies, such as 60 hertz (Hz), to pass.
Firmware - Software that is stored in semiconductor memory such as ROM, EPROM or EEPROM. Firmware is typically an embedded instruction set to control the operation of logical hardware found in monitoring and/or control systems.
Flame retardant - The materials will not support combustion on their own and will in fact help suppress combustion. This applies to the battery case materials, wire insulation, switches, circuit breakers, fuse holders, and connector bodies.
Float Charging - The battery charging mode for which sealed lead acid batteries are designed. The float voltage is the ideal maintenance voltage for the battery, which maximizes battery life. When the float voltage is applied to a battery, a current known as the float current flows into the battery, exactly canceling the batteries own internal self-discharge current. Sealed lead acid batteries require float charging at least occasionally or they will become permanently degraded by a process called sulfation. Maximum lifetime is obtained when a sealed lead acid battery is permanently float charged.
Flyback Converter - Also called a buck-boost converter, this topology typically uses a single transistor switch and eliminates the need for an output inductor. Energy is stored in the transformer primary during the first half of the switching period when the transistor switch is on. During the second half or flyback period when the transistor is off, this energy is transferred from the transformer secondary. Also see Boost Regulator, Buck Regulator, Bridge Converter, Forward Converter, Push-Pull Converter and Resonant Converter.
Flux - The lines of force of a magnetic field.
Forward Converter - Also called a Buck-Derived converter, this topology, like the flyback converter, typically uses a single transistor switch. Unlike the flyback converter, energy is transferred to the transformer secondary while the transistor switch is on, and stored in an output inductor. See Boost Regulator, Buck Regulator, Bridge Converter, Flyback Converter, Push Pull Converter and Resonant Converter.
Forward Transfer Impedance - The amount of impedance placed between the source and load with installation of a power conditioner. With no power conditioner, the full utility power is delivered to the load; even a transformer adds some opposition to the transfer of power. On transformer based power conditioners, a high forward transfer impedance limits the amount of inrush current available to the load.
Frequency - The number of cycles (oscillation positive and negative) completed in one second. Defined as Hertz (Hz). In North America, utility power is generally 60 cycles per second or 60 Hertz. Many countries based on European standards use 50 Hertz. Aircraft typically use 400 Hertz.
Frequency Converter - A unit that changes the power from one frequency to another frequency (i.e. from 120 vac, 400 Hz input to 120 vac, 60 Hz output). Input and output voltages may also be converted as well.
Frequency Variations - A change in frequency from the normally stable utility frequency of 50 Hz, 60 Hz or 400 Hz. This may be caused by erratic operation of emergency generators or unstable frequency power sources. For sensitive electronic equipment, the result can be data corruption, hard drive crash, keyboard lockup and program failure.
Full Bridge Converter - Converter topology that typically operates as forward converter but uses a bridge circuit, consisting of four switching transistors, to drive the transformer primary. Also see Bridge Converter.
Full Height (FH) - Refers to a computer device that requires a full size drive bay or space, typically 5.25” wide
Fuse - A one-time over current protection device employing a fusible link that melts (blows) after a certain current level is exceeded for a certain length of time. A device that breaks, thereby opening the circuit and protecting the equipment connected to it, when the current passing through it exceeds its rated value. A fuse can be used only once, whereas a circuit breaker, which accomplishes the same thing, can be reused. (Compare to Circuit Breaker.)
Full Load - The greatest load that a circuit is designed to carry under specific conditions; any additional load is considered an overload.
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Galvanic Isolation - A characteristic of an isolation transformer whereby the output is electrically disconnected from the input. Power is coupled from input to output by magnetic fields in a transformer. A galvanically isolated output is considered to be a separately derived source according to the NEC, and is required to be grounded. See Isolation Transformer.
Gauss - The CGS unit of measurement for flux density. One Gauss is equal to 1 Maxwell per cm2.
Generator - A gasoline, natural gas, or propane powered engine that produces electricity. Generators are often used with uninterruptible power supply (UPS) systems. Since generators require a few minutes to stabilize after being started, UPS's are often used for short duration outages and generators reserved for longer power interruptions. Some less sophisticated generators may have a problem with frequency regulation, never appearing to the UPS as a stable power source.
Global UPS (GUPS) - Refers to an UPS being able to operate from either standard US power (120 vac. 60 Hz) or standard European power (220 vac, 50 Hz). This covers 95+% of the world.
GND, GRD or G - Ground termination point on equipment. See Ground.
Ground - An electrical ground in a power system is a conductor that is effectively connected to the earth, hence the term "ground". The primary purpose is connect equipment chassis to ground so that it is at the same voltage potential as the ground reduce potential shock hazards to users.
Ground Fault Circuit Interrupter (GFCI) - An electrical device that senses any differential current in connected conductors to determine if there is ground current. If the level exceeds its threshold, the GFCI disconnects the circuit.
Ground Loop - Condition caused when two or more system components share a common electrical ground line. A feedback loop is unintentionally induced, causing unwanted voltage levels.
Guarded switch/CB/etc. - Providing barriers on all sides of the device to help prevent damage or accidental operation of the device. Also allows for locking the device in a particular position for operational or safety reasons.
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Half Bridge Converter - Converter topology that typically operates as a forward converter but uses a bridge circuit, consisting of two switching transistors, to drive the transformer. Also see Bridge Converter.
Hardwired - Describes any equipment connected to its power source by hardware attached directly to terminal blocks or distribution panels.
Harmonic Distortion - The presence of harmonics that change the AC voltage waveform from a simple sinusoidal to complex waveform. Harmonic distortion can be generated by a load and fed back to the AC utility line, causing power problems to other equipment on the same circuit.
Henry (H) - The unit for inductance.
Hertz (Hz) - Or Cycles, used for frequency measurement, 1 cycle per second is equal to 1 Hz.
Hi-Pot - High Potential. Usually refers to a test conducted utilizing a high potential voltage to determine a piece of equipments dielectric withstand capability per safety agency requirements.
Hot-Swappable Batteries - A feature which enables the user to change batteries without powering down the connected load. Or: A feature that allows an uninterruptible power supply (UPS) battery to be changed for maintenance without taking the UPS and the equipment connected to it, off-line.
Hot-Swappable Power Modules - A feature which enables the user to change power modules without powering down the connected load.
Hz - Hertz; frequency measurement, 1 cycle per second is equal to 1 Hz.
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IEC - International Electro-Technical Commission, a global organization that sets standards for safety of equipment, primarily electrical.
IEEE - Institute of Electrical and Electronic Engineers, a worldwide organization that helps set electrical performance standards.
Immobilized electrolyte - The battery electrolyte is suspended in absorbent materials between the lead plates resulting in no free liquid. This prevents the electrolyte from leaking if the battery case were somehow damaged.
Impedance - The unit of measure that represents the opposition or resistance (to impede) current flow in AC circuits, i.e. Resistance, Inductive reactance (inductive loads), Capacitive reactance (Capacitive loads).
Since pure resistive loads do not cause a “Phase Shift” between current and voltage and Inductive or Capacitive loads do, Impedance should be thought of as the combined Resistive effect of Resistive, Inductive, and Capacitive loads upon an electrical circuit. (See “Z” or Impedance)
Inductance - That property of a circuit element that tends to oppose any change in the current flowing through it. The inductance for a given inductor is influenced by the core material, core shape and size, the turns count of the coil, and the shape of the coil. Inductors most often have their inductance values expressed in microHenries (µH) or milliHenries (mH).
Inductor (Choke) - A passive component designed to resist changes in current. Inductors are often referred to as AC Resistors. The ability to resist changes in current and the ability to store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field. A changing magnetic field induces a voltage that opposes the field-producing current. This property of impeding changes in current is known as inductance.
Input Branch Circuit - The Input Circuit from the facility Power Panel circuit breaker to the electronic equipment module.
Input Line Filter - A power filter placed on the input to a circuit or assembly that attenuates noise introduced from the power bus. The filter is designed to reject noise within a frequency band. Typically these filters arc low-pass filters meaning they pass low frequency signals such as the DC power and attenuate higher frequency signal which consist of mainly noise. Band pass or low pass filters are commonly made up of inductor and capacitor combinations.
Input - The switch on the front panel that turns the equipment ON or OFF. When the Input Main switch is set to ON, power is available at the output receptacles of the unit. When set to OFF, no power is available at the output receptacles of the unit.
Input Surge Current - See Inrush Current.
Inrush Current - The momentary peak input current required by electrical equipment when energized. For example, the magnetizing current when energizing a transformer is typically several times the steady state current.
Inrush Current Limiting - Protection circuit that limits the current a converter draws at turn on.
Inverter - An electronic device or electronic circuitry that converts DC battery power to AC power (DC/AC). At the present time most computer equipment requires AC power for operation.
Internal Bypass - UPS circuitry that provides a redundant power path. If there is an internal UPS fault, the connected load will still be supplied with unconditioned utility power.
Isolation - The separation (often through the use of an isolation transformer) of one section of a system from undesired electrical influences of other sections.
Isolation transformer - A transformer with separate primary and secondary windings and generally a shield between. The main purpose is to allow re-referencing of output connections and to reduce conducted electrical noise. A multiple-winding transformer with physically separate primary and secondary windings. Although the two windings are physically disconnected, the magnetic field in the windings of the primary creates (induces) electrical power in the secondary winding. In this way the electrical power available at the input can be transferred to the output. An isolation transformer does not transfer unwanted noise and transients from the input circuit to the output windings. This attenuation, or reduction in amplitude, could be as high as one million to one.
ITI - Information Technology Industries Council. See CBEMA.
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Joule - The mks unit of work or energy equivalent to heat generated in 1 second by 1 ampere flowing through 1 ohm. A watt/second. A measurement of work in time. 1 joule equals 0.0002778 watt/hours. 1-kilowatt hour is equivalent to 3,600,000 joules.
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kcmil - Thousand Circular Mil; wire size for multiple stranded conductors over 4/0 AWG in diameter. Formerly
MCM.
k - kilo, used to express 1000 (10 to the +3rd power) times the standard unit.
KV - kilo-Volts; 1000 Volts potential.
KVA - kilo-Volt-Ampere; 1000 Volt Amperes; a measure of apparent power. (KVA: An acronym for kilovolt-amps (See VA) that is a measure of apparent power; 1 kVA = 1000 VA)
KW - kilowatt; 1000 Watts; An acronym for kilowatt (See Watt) that is a measure of real power; 1 kW = 1000 Watts.
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Lagging Load - An inductive load with current lagging voltage. Since inductors tend to resist changes in current, the current flow through an inductive circuit will lag behind the voltage. The number of electrical degrees between voltage and current is known as the phase angle. The cosine of this angle is equal to the power factor (linear loads only).
LAN - Local Area Network. See Ethernet. The means by which a local community of users and workgroups can share information and resources electronically.
LED - Light Emitting Diode, a high reliability, illuminating device used as an indicator of state or status. Available in red, green, amber and blue.
Leading Load - A capacitive load with current leading voltage. Since capacitors resist changes in voltage, the current flow in a capacitive circuit will lead the voltage.
Leakage Current - The current flowing from the input terminals of the electrical equipment and the chassis at a specified voltage. This is a safety consideration so designs minimize this current to typically less than 5 mA for commercial systems and less for military and medical systems.
Line Conditioner (Power Conditioner) - Often a transformer device that acts to smooth out fluctuations in input voltages and provide near-uniform voltage and voltage waveforms.
They are devices that are used to optimize the quality of commercially supplied power. By definition, an uninterruptible power supply (UPS) system is a line conditioner, but a line conditioner is not always a UPS system.
Line Interactive - A UPS containing an off-line inverter that must transfer on during a blackout, but provides faster transfer times than an offline UPS. Power conditioning and surge suppression are provided to protect the connected load.
Linear Load - A load in which the current relationship to voltage is constant based on a relatively constant load impedance.
Load -Equipment that receives power from a power supply, UPS or PDU. (A Load can also be an Electrical Device or Transducer, that converts energy from one form to another)
Load Segments - Groups of receptacles on the rear panel of a power supply or UPS that can be independently controlled.
Load Sequencing - The ability to selectively turn on or off specific loads in a preset pattern. Some UPS and PDU models are able to perform load sequencing on startup and/or shutdown. Benefits include reduced inrush and ability to start a specific load before another is started.
Load Shedding - The ability to selectively shut off a set of output receptacles, extending the capacity of the UPS battery. Some PowerStation UPS models are able to shed less critical loads by turning off selected output receptacles during an extended power failure while maintaining power to the more critical load(s) on the remaining output receptacles.
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M - Mega, used to express 1,000,000 (10 to the +6th power) times the standard unit, i.e. MVA.
µ - micro, used to express 0.000001 (10 to the -6th power) times the standard unit, i.e. µF
m - milli, used to express 0.001 (10 to the -3rd power) times the standard unit, i.e. mA
Magnetic Synthesizer - A three-phase ferro-resonant based system with zigzag output windings to allow the Ferro to handle unbalanced loads.
Maintenance free battery - This means that during the normal operation of the battery, there will not be a need to add water or electrolyte.
Make-Before-Break - Operational sequence of a switch or relay where the new connection is made prior to disconnecting the existing connection.
Manual Bypass Switch - (MBS) A manually operated transfer switch used to bypass the major electronics in the UPS, so the UPS can be serviced without power interruption.
MIB - Management Information Base. The database of information (or variables) related to a particular network device or collection of network devices. The MIB is a collection of stored guidelines that allow a NMS to know what information can be provided by the various devices on the network which might be polled for status information. The popularity of SNMP has resulted in the development of standards for storing data critical to network operation, the
Management Information Base (MIB). MIB-II, the latest generation of network management MIBs, stores data on TCP/IP traffic, routing, configuration and errors. MIB-II has improved support for multi-protocol devices and allows the NMS to control SNMP operation
MOV - A Metal Oxide Varistor. A MOV is a voltage sensitive breakdown device that is often used to limit over voltage conditions (electrical surges) on power and data lines.
When the applied voltage exceeds the breakdown point, the resistance of the MOV decreases from a very high level (thousands of ohms) to a very low level (just a few ohms).
The actual resistance of the device is a function of the rate of applied voltage and current. A varistor is a very rugged voltage-clamping device capable of absorbing very large current variations without being damage.
MOV's are commonly used in Power Strips. If your power strip has more than two MOV's you likely have a fairly high quality device. They look like largish disk type capacitors.
MTBF - Mean Time Between Failure. The measurement of the reliability of equipment expressed in the average operational hours before a service interrupting failure. Based upon either actual operating data or calculated data per MIL-HDBK 217.
MTTR - Mean Time To Repair. The time to repair a piece of equipment on the average.
Multinational Input - Refers to ETI products being able to operate from standard voltages of 100 vac, 120 vac, 200 vac, 220 vac or 240 vac having either a 50 or 60 Hz frequency. This covers 99+% of the world.
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n - nano used to express 0.000000001 (10 to the -9th power) times the standard unit, i.e. nA
NEC - National Electrical Code (ANSI/NFPA 70, latest issue), guidelines used by local electrical manufacturers and contractors to insure safer and consistent installations. Developed by the National Fire Protection Association of Quincy, Mass. First published in 1896.
NEMA - National Electrical Manufactures' Association. Helps set electrical product standards, i.e. electrical plug and outlet configurations.
Network Transient Protector - An in and out RJ11 jack for telephone/modem protection or RJ45 for 10Base-T network cable. It isolates connected equipment such as modem and fax machines from “back door ”power surges.
Neutral - Generally refers to the AC power conductor that is common in polyphase systems (i.e. neutral in a 3-phase WYE) or the conductor that is referenced to ground at some point.
NFPA - National Fire Protection Association. Parent organization for NEC.
NMS - Network Management Device. A system responsible for managing at least part of a network. NMS communicate with agents to help keep track of network statistics and resources. See SNMP Agent.
Noise (audible) - Random, sporadic, or multi-frequency acoustical signals that is generated by the operation of equipment. Since audible noise can be distracting or annoying to the user, designs try to minimize their levels.
Noise (electrical) - Random, sporadic, or multi-frequency electrical signals that become part of a transmission making the signal or information more difficult to identify. Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) that causes undesirable effects in the circuits of computer systems. Sources of the problem include electric motors, relays, motor control devices, broadcast transmissions, microwave radiation, and distant electrical storms. RFI, EMI and other frequency problems can cause data error, data loss, storage loss, keyboard lockup and system lockup.
Nominal Value - A designated value that has been accepted for the sake of convenience. For instance, nominal voltages are values assigned to circuits so that the voltages of the circuits can be conveniently discussed as 120 Vac nominal units, or 230 Vac nominal units.
Nonlinear Load - A load in which the current does not have a linear relationship to the voltage. In a light bulb, the current is directly proportional to voltage at all times. In a nonlinear load such as switched mode power supplies, the current is not directly proportional to voltage. The peak current of a nonlinear load is greater than a linear (sinusoidal) load.
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OCONUS - Off Continental United States. Refers to an electronic device being able to operate from other than US power, i.e. standard European power (220 vac, 50 Hz).
OEM - Original Equipment Manufacturer.
Oersted - The unit of magnetic field strength (H) in the CGS system. One Oersted equals the magnetomotive force of one Gilbert per centimeter of flux path.
Offline UPS - The unit passes the commercial power to the load normally. When it detects a voltage too low, it turns on its inverter. The delay between utility power loss and inverter startup can be long enough to disrupt the operation of some sensitive loads. Also called a standby UPS. This technology does not provide full time power conditioning. This technology is less reliable overall than on-line at protecting the load from all forms of power disturbances.
Ohm (©) - The electrical unit of measure for resistance.
Ohm Law - The relationship between voltage (pressure), current (electron flow), and resistance. The current in an electrical circuit is directly proportional to the voltage and inversely proportional to the resistance. E=IR, or I=E/R, or R=E/I. Where E=voltage, I=current, and R=resistance.
One-line Diagram - A schematic of a single phase or polyphase system represented by a single line for all phases.
Online UPS - The technology that fully converts AC power to DC power then back to AC power. This technology provides full power conditioning and protects the load from all forms of power disturbances, including brownouts, blackout, transient surges or sags. In the event of a utility power failure, there is no delay or transfer time to backup power.
Orderly Shutdown - The process of sequentially closing down hardware and/or software processes so that no corruption of data occurs and/or no safety hazards are created.
OSHA - Occupational Safety and Health Act. Federal Safety Regulations applied to the workplace.
Outage: A long-term loss of electrical power.
Outlet - Any point on a wiring system where current is taken to supply electrical power for a load.
Over current Protection - The circuit or device that protects the equipment from exceeding a specific current level, including short circuit. See Fuse and Circuit Breaker.
Over-temperature Protection - Design feature that protects the silicon die from exceeding its designed operating temperature range. The device will thermally cycle until the abnormal condition is corrected.
Overload - A condition in which the load wants more from the power source (such as a UPS) than the power source has been designed to supply.
Over Voltage: By definition, a voltage that is at least 10% above the nominal or normal level. The “Nominal Level” of a 120vac supply circuit is 117v. The nominal of 117v plus 11.7v, or 128.7v would be considered “Over Voltage”. (See Spike and Surge.)
Over Voltage Protection - The circuit or device that prevents the output from exceeding a specific voltage level by either clamping output or shutting down the power supply.
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p - pico used to express 0.000000000001 (10 to the -12th power) times the standard unit, i.e. pF
Parallel Online UPS - Online UPS technology that provides redundant sources of conditioned backup power so that the critical load is protected even in the event of UPS component failure.
Peak Voltage - Is a measure of an AC waveform of the highest peak voltage present on the waveform (positive peak occurs at the 90 degree point of a normal sine wave). A proper 120V AC waveform will have a peak voltage of about 170 volts, (120v X 1.414 = 169.68v). Also see RMS value.
Peak to Peak Voltage - Peak-to-peak voltage, for a normal sine wave is two times peak. It represents the positive peak at 90 degrees PLUS the negative peak at 270 degrees on a normal sine wave. AC waveform of the highest peak-to-peak voltage present on the waveform. A proper 120V AC waveform will have a peak voltage of about 170 volts, (120v X 1.414 = 169.68v). The Peak to Peak voltage is 170v X 2, or 340 volts. Also see RMS value. (So when you get shocked at 120v, you are actually receiving 340v peak to peak. Now you know why it hurts so much.)
This also explains why an electrical component that operates at 120v has an electrical voltage rating of 330, or 340volts. It must be capable of operating safely over the full peak to peak voltage range.
Phase Shift - A phase shift is a distortion of a sine wave on its horizontal axis that represents time. (The vertical axis represents magnitude. The vertical axis is where surges, spikes, and transient pulses live). Time distortion is just as critical as magnitude distortion because it disrupts the smooth or linear flow of voltage, current, or power.
PDU - Power Distribution Unit. This electrical device is used to control the distribution of power to the individual loads. Control may be as simple as a series of switch or circuit breakers to interlocked logic operating solid-state relays. Available as a stand-alone unit or integrated into the UPS.
Power Factor (PF) - Power Factor, the cosine of the phase angle between the Watts (real power) used relative to the VA (apparent power), (Watts = VA x PF). Can be expressed as a percent or decimal number, i.e. a PF of 0.65 is the same as a PF of 65%.
Power factor values are the result of AC resistive values called reactance. Reactance can be either Capacitive Reactance XC or Inductive Reactance, XL.
Power Factor Correction (PFC) - An active or passive input circuit to change the power factor of the input current to a device so that it is closer to a PF of 1.0. Numerous benefits include reduced input line current and lower input harmonics.
Power Conditioner (Line Conditioner) - A unit that provides clean, well-regulated power. Input and output voltages may also be converted as well.
Power Management Software - Provides monitoring and shutdown for UPS and connected load.
Push-Pull - Converter topology usually configured as a forward converter, but uses two transistor switches and a center tapped transformer. The transistor switches turn on and off alternately. Also see Boost Regulator, Buck Regulator, Bridge Converter, Flyback Converter and Resonant Converter.
PWA (PCA) - Printed Wiring Assembly (Printed Circuit Assembly) refers to the individual assembled electronic cards used in an electronic product.
PWB (PCB) - Printed Wiring Board (Printed Circuit Board) refers to the bare circuit cards used in PWAs.
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Q (Q Factor) - A measure of the relative losses in an inductor. It is also known as the quality factor, defined as the ratio of inductive reactance to effective resistance. Q is zero at the SRF of an inductor.
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Rack - A mechanical structure for mounting electrical equipment. Size and mounting patterns are defined by EIA 310.
Rack unit (U) - A common increment of equipment space height as defined by EIA 310. Typically 1 U equals 1.75 inches in height. Racks are sized in whole number of unit, i.e. A 45 U rack has 78.75 inches of panel space.
Rackmount - A piece of electronic equipment such as a UPS that can be mounted in a rack along with servers, hubs, and other devices.
Receptacle - A contact device installed at an outlet designed to accept a single plug. Receptacles on the rear of a UPS accept plugs from supported system equipment such as computers or monitors.
Rectifier - An electronic device that converts AC power to DC power (AC/DC)
Redundancy - Duplication of elements in a system or installation to enhance the reliability or continuity of operation.
Regulation - A method of limiting voltage to a narrow range.
Redundant Operation - Parallel configuration of converters used in distributed power system to increase system reliability. Converters may be used in a N+1 architecture.
Remote Sensing - Using sense leads connected at the output load provides feedback to voltage regulation circuits of a converter. This arrangement is used to compensate for voltage losses from long leads to a load.
REPO - Remote Emergency Power Off. See Emergency Shutdown.
Resonant Converter - Switching converter technology in which a resonant tank circuit operating at very high frequencies is used to transfer energy to the output.
Response Time: The time it takes for a UPS, conditioner, suppressor, fuse, or circuit breaker to sense and react to an electrical surge or spike.
Reverse Voltage Protection - Converter feature that prevents damage to internal components if a reverse voltage is inadvertently applied to the input or output terminals.
RMS - Root Mean Square. The square root of the average value of the squares of all instantaneous values of voltage or current during one half cycle in an AC circuit. For an ideal sine wave, the RMS value is approximately equal to 0.707 times the peak value of the waveform. RMS is often called the effective value. This term can also apply to RMS voltage, current or power.
So Remember, when you are paying out those hard earned $$$ for a high end, high power audio system on your home entertainment center, unless the power output ratings are shown in “RMS Power”, it is dramatically over-stated. The peak power is normally peak-to-peak power, which must be divided in half, and then multiplied by the .707 factor.
If the power rating is in instantaneous peak-to-peak values at some specific frequency, go spend your money with a reputable audio manufacturer. You do not need to be over-paying for something you won't get. RMS power output is the only accurate measure of actual power you can obtain.
Rolling Blackout - A condition where power utilities purposely impose blackouts or brownouts over a broad portion of their service area to free up capacity so that the remaining service area can continue to be served. After a time, another portion of the service area has a blackout imposed on it, so that power can be restored in the original area. (By regulation, power utility companies must supply a nominal value of 117v on a 120v line to your panel board)
Rolling Brownout - A condition where power utilities purposely impose brownouts (lower voltage levels) over a portion of their service area to free up capacity so that the remaining service area can continue to be served. After a time, another portion of the service area has a brownout imposed on it, so that power can be restored to normal conditions in the original area. . (By regulation, power utility companies must supply a nominal value of 117v on a 120v line to your panel board)
RS-232 - Also called serial ports; a method of communicating digital information in which the data bits are transmitted sequentially over one line.
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Sags - When the line voltages drop to 80 to 85 percent below normal for short periods of time. Possible causes are heavy equipment being turned on, large electrical motors being started, and the switching of power mains (internal or utility). Power sag can have effects similar to those of a power surge, such as memory loss, data errors, flickering lights and equipment shutoff. (Also See Under voltage)
SCADA - Supervisory Control And Data Acquisition. Remote monitoring and control of various equipment and
loads.
Scalable UPS - A UPS that allows for expandability; for example, enables a UPS to accommodate a larger load by purchasing additional power modules.
SCSI - Small Computer Standard Interface.
Separately Derived Source - A source of AC power which has its neutral wire locally derived from the ground wire. In an AC power distribution system, wiring regulations dictate that the neutral is connected to ground only once, and that is at the service distribution panel. The point of power utilization may be at a considerable distance from the neutral grounding point, allowing for the introduction of Common Mode noise. The most effective way to eliminate common mode noise is to connect the neutral directly to ground at the point of utilization, which would violate wiring regulations. It is allowable under the regulations to connect a lead from an isolated power source to ground at any point. Therefore, an isolation transformer at the point of utilization may be used to create an isolated power source which can then have its neutral lead connected to ground, creating a separately derived source. The isolation transformer may be a separate device or it may be built into another unit, such as a UPS.
Series Operation - Master-slave configuration in which two or more isolated converters are connected to obtain a higher output voltage level (converter inputs connected in parallel) or wider input voltage range (converter inputs connected in series) than that obtainable from one module.
Series Redundant - UPS configuration whereby one UPS feeds a second UPS, both with a bypass circuit. The load is connected to the second UPS. If the source fails, the first UPS uses its batteries. When they are exhausted, the second UPS batteries take over. If either UPS were to have a failure, the other continues operation.
Shielding - A method of blocking electromagnetic interference to protect sensitive devices. In an inductor this is placed in the form of a thin metal sheet, a winding, or the core itself can act as a shield.
Short Circuit - When two wires become connected, usually by accident, resulting in a system malfunction. In a data circuit, the malfunction may be a loss of signal or information. In an AC power circuit, a short may result in large, uncontrolled current flow which might cause overheating of wiring or cause over current protective devices such as fuses or circuit breakers to operate.
Sine Wave - The ideal sinusoidal waveform exhibited by alternating current. It is the shape of an ideal AC waveform. Most high-end uninterruptible power supplies (UPS's) provide an accurate and linear sine wave. Some less sophistical UPS's produce a square wave, or a distorted sine wave that may cause some devices to not work properly or to shorten their life span or that of the components they feed. (See Clean Power)
Single-Phase Power (1Ø) - Power that is provided by a single source that normally includes one hot lead and a grounded return line (neutral).
Single-Point Ground - Tying the power neutral ground and safety ground together at the same point, thus avoiding a differential ground potential between points in a system.
Sinusoidal - Adjective to describe a function that follows a sinewave.
SNMP - Simple Network Management Protocol. A request-response protocol that collects management information from network devices and provides a way to set and monitor configuration parameters. This system is an open system that has been adopted by many users and equipment manufacturers. A device managed by
SNMP must have a MIB and an Agent.
SNMP Agent - Software that monitors and manages a specific network device. It maintains that device's MIB and responds to requests from the NMS. In a UPS or PDU with SNMP, the agent can reside in the equipment, or in a SNMP adapter, or in a host computer connected to the equipment.
Specific Gravity (SG) - The ratio of the weight of a given volume of substance (such as electrolyte) to that of an equal volume of another substance (such as water) used as a reference. Used as a measure of the charge state of a wet cell battery.
Spike - A high voltage condition that lasts for a short duration of time, normally less than a milli-second. Spikes are instantaneous and cause a tremendous increase in voltage.
A sudden, rapid voltage peak that can often be thousands of volts. Spikes can be the result of nearby lightning strikes, but there can be other causes as well.
Spikes effects on vulnerable electronic systems can include loss of data and damaged circuitry. Static electricity is an example of discharges that can be considered to be Spikes. Lightning is the instantaneous discharge of static electrical charges.
Square Wave - Output waveform generated by very basic, low-cost UPS's. Functions adequately for less sensitive loads, but may not provide acceptable quality input for some types of electronic equipment.
Square wave outputs can be undesirable waveforms for critical computing applications, as it is harder on equipment and may cause undesired side effects. (Compare to Sine Wave.)
Standby Power System - See Off-Line UPS.
Standby UPS - An uninterruptible power supply (UPS) that passes line power straight through to the output when conditions are stable, but switches to battery power when line voltage drops are encountered.
Static regulation - The ability to hold the controlled level to specification with no variation in other parameters, i.e. static voltage regulation.
Status LED's - Light Emitting Diodes (LED's) that show the status of the UPS when they light up or turn off. Also common to many other applications in computers and electronics.
Step Wave - (Modified Sine wave) Enhanced version of square wave that provides adequate input for some more sensitive loads, but still not as high quality as a sine wave.
Surge - A transient wave of current, potential (voltage) or power in an electric circuit that usually has a high rate of change that is outside of normal tolerances. Over-voltage transient surges can seriously damage equipment. Any surge can cause erratic operation, loss of data or damage to loads. Under this condition, computer systems may experience memory loss, data errors, flickering lights and equipment shutoff.
A Surge can represent a substantial increase in voltage lasting a small fraction of a second. They are often created when high-powered appliances such as air conditioning compressor motors, ventilation systems, transformers, or other high-power reactive loads are switched on or off.
Surge type voltage increases can continue for several cycles or more. (See Over-voltage and Spike.)
Surge Suppressor - A device or circuitry normally consisting of MOV's, Capacitors, Rod-core Inductors, etc that is designed to limit or suppress transient surges and spikes to acceptable levels.
The joule rating that is applied to surge protection devices represents the amount of energy that the device can absorb before it becomes damaged.
In comparing surge protection performance, the Joule rating of a surge suppressor is less important than the “let-through” voltage rating. This reflects the fact that surge suppressors may protect equipment by deflecting surges as well as absorbing them.
There is no established standard for measuring or comparing the joule rating of surge suppressors. This results in exaggerated claims relating to the actual level of protection provided by surge suppressors.
Switchmode - A power conversion technique that involves breaking the input power into pulses at a high frequency by switching it on and off and recombining these pulses at the output stage. Using this technique, an unregulated input voltage can be converted to one or more regulated output voltages at relatively high efficiencies. This type of power supply design is used by most modern electronic devices, especially computers. Switchmode supplies are economical, but draw non-linear current with a high crest factor and numerous harmonics.
Synchronization - The process of bringing two sources of AC power into alignment such that there is no phase difference between the sine waves and they are at the same frequency. In a UPS, one of the sources of AC power is usually the utility power that cannot be changed. Therefore, synchronization is accomplished by adjusting the phase of the UPS inverter.
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Technician - Refers to an electronic technician qualified to maintain and repair electronic equipment. Not necessarily qualified to install electrical wiring. Compare to Electrician.
Temperature Derating - Reducing the overall capacity of a power supply to account for an elevated temperature ambient. See Derating.
Terminal Block - An insulating base equipped with terminals for connecting secondary and control wiring. Used on hardwired equipment, such as a UPS, when input plugs and output receptacles are either impractical or unavailable.
Terminal - A connector for attaching a conductor to an electrical apparatus.
Thermal Protection - A device or circuit designed to protect the equipment from damaging temperatures. Some UPS and PDU's are capable of doing this for their connected loads.
Three-Phase Power (3Ø) - Power that is provided by a single source with three outputs with a phase difference of 120° between any two of the three voltages and currents.
Toroidal Inductor - An inductor constructed by placing a winding(s) on a core that has a donut shaped surface. Toroidal cores are available in many magnetic core materials within the four basic types: Ferrite, Powdered iron, Alloy and High Flux, and Tape Wound. Characteristics of toroidal inductors include: self-shielding (closed magnetic path), efficient energy transfer, high coupling between windings and early saturation.
Total Harmonic Distortion (THD) - The square root of the sum of the squares of the RMS harmonic voltages or currents divided by the RMS fundamental voltage or current. Typically a supply sine wave is considered acceptable when THD levels are 5% or less. See harmonics, harmonic distortion and distortion. Can also be calculated in the same way for only even harmonics or odd harmonics.
Transducer - A device that senses one form of energy and converts it to another, i.e., temperature to voltage (for monitoring).
Transfer Switch - A switch that will transfer current from one circuit path to another without interrupting the flow of the current. A switch used to transfer a load between a UPS and its bypass source.
Transfer Time - The amount of time it takes to sense a power failure and to switch from A C line power to battery or inverter power. This is applicable to standby or offline UPS systems. True online UPS systems do not allow an interruption in the power to the load.
Transformer - (T) A device that is used to change the proportions of AC voltage or Current between its primary and secondary windings. Transformers are used to step-up (raise) or step-down (lower) AC voltage or current proportions between their primary and secondary windings in proportion to the transformer turns ratio.
When used to alter current, transformers are called current transformers. When used to alter voltage, they are called voltage transformers. Often referred to as “Power Transformers” because voltage and current together represent electrical power.
Another important application of the transformer is “Isolation” (or matching). Since the only coupling between primary and secondary windings in a transformer is magnetic, transformers can be used to physically isolate the source from the load by eliminating hard-wired electrical connections between windings.
Transient - The fast radical change in a smooth sine wave that occurs in both voltage and current waveforms during the transition from one steady-state operating condition to another. Transients take place when there is a rapid voltage peak of up to 20,000 volts with a duration of 10 microseconds to 100 microseconds. They are commonly caused by arcing faults and static discharge. In addition, major power system switching disturbances initiated by the utilities to correct line problems may happen several times a day. Effects can include memory loss, data error, data loss, and component stress.
Transient Response Time - The time from a step change in load, voltage or other parameters until the power supply output recovers to nominal specification.
Transient Suppression - See Surge Suppressor.
Transverse Mode Noise - Normal mode. An undesirable voltage which appears from line to line of a power line.
Transverse Mode Noise Rejection (TMNR) - The ability of an electronic device, like a UPS, to block transverse mode noise between input and output.
Trickle Charging - With the trickle charging process, the battery receives a constant voltage feeding a low current. Constant use of this method dries the electrolyte and corrodes the plate, reducing potential battery service life by up to 50 percent.
Two-Phase Power (2Ø) - Power which is provided by a single source with two outputs which may be 180 degrees out of phase or 120 degrees out of phase.
Turns Ratio - The ratio of the primary voltage (or turns) to the secondary voltage (or turns) in a transformer.
TÜV - A European safety agency that sets standards for product safety. See CE, UL, ETL, CSA and VDE.
TVSS - Acronym for Transient Voltage Surge Suppressor. Another term for surge suppressor taken from the UL designation for this type of product. See Surge Suppressor.
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xU - x Rack Units. Each Rack Unit is 1.75 inches in height. Width depends on the rack width, i.e. 19 or 23-inch width. Most rack equipment panel heights are in full rack units, not fractional, i.e. 3U.
UL - Underwriter's Laboratories, Inc. A US independent safety agency that sets standards for product safety. See ETL, CSA, CE, VDE and TÜV.
UL Listed - A UL Listed product has met to applicable UL Standard for that class of equipment. Listed products are typically end products and not components.
UL Recognized - A UL Recognized device has met to applicable UL Standard for that class of device. Recognized components are typically parts that go into making the finished product.
Under voltage - By definition, under-voltage represents a voltage at 90% or less of the normal level for more than one minute. The result of under-voltage is sometimes called a brownout condition.
UPS - Uninterruptible Power S |
