Power & Product Glossary

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Alternating Current electrical power supplied by a utility company or from an AC generator.

AC Distribution
A module in the Eaton power system that distributes AC power to other Eaton power system modules.

AC Metering
Measurement of AC power input voltage and current parameters by sampling. The results of the measurements are used to calculate the rms equivalents for voltage, current and power, and also calculate the power factor and frequency.

AC Utility
The electric power furnished by an electric power utility company.

Active Load Share
A current sharing scheme controlled by the supervisory module that adjusts the output voltage of individual rectifiers so that all rectifiers in a DC power system produce the same output current.

Active Voltage Control
The supervisory module adjusts the rectifier output voltages to maintain a constant DC power system voltage (measured at the output or battery) independent of load fluctuations during normal operation.

Advanced Battery Management
A three-stage charging technique that automatically tests battery health. Provides advance notification when preventive maintenance is needed, allowing ample time to hot-swap batteries without ever having to shut down connected equipment significantly extending the life of your UPS's battery (and, quite possibly, your contract).

A software program that acts as a focal point for data collection and configuration of a specific network entity (hardware or software). SNMP agents provide data to management stations regarding the operation and configuration of devices on a network.

Alternating Current (AC)
An electric current that reverses its direction at regularly recurring intervals, as opposed to direct current, which is constant. Usually in a sine wave pattern, for optimal transmission of energy.

Ampere (Amp or A)
The unit of measure for the rate of flow of electricity, analogous to gallons per minute. VA x 0.7 (power factor) = watts

Apparent Power
Applied voltage multiplied by current in an AC circuit which doesn’t take the power factor into account. Unit is volt amperes (VA).

Sparking that results when undesirable current flows between two points of differing potential due to leakage through the intermediate insulation or a leakage path due to contamination.

Audible Noise
A measure of the noise emanating from a device at audible frequencies.

Active Voltage Control

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Backup Time
The amount of time the battery in a UPS is designed to support the load.

Balanced Load
AC power system using more than two wires, where the current and voltage are of equal value in each energized conductor.

The data a cable can carry measured in bits per second (bps).

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 Capacity
The battery ampere-hour capacity at full charge, standard temperature, and at a specified (usually C10) discharge rate.

Battery Charger
A device or a system which provides the electrical power needed to keep the battery backup fully charged.

Battery Current Limit
System voltage control that limits the battery charge current to a preset value.

Battery String
A group of batteries connected together in a series.

Bi-Directional Converter
A device which changes (or converts) alternating-current power to direct-current power and vice versa.

Blanking Panels
Steel or plastic plates that are inserted in empty U spaces at the front of a rack or enclosure. They are used to improve airflow for the installed equipment and to reduce hot and cold air recirculation and remixing within the rack. Also referred to as filler panels.

Blanking Panels

See buck and boost.

British Thermal Unit (BTU)
Used to measure heat dissipation and is the amount of energy required to raise one pound of water one degree Fahrenheit. One pound of water at 32°F requires the transfer of 144 BTUs to freeze into solid ice.

Brown Field
An existing data center—often with limited possibilities for sustainable and energy-efficient designs.

A steady state of low voltage, but not zero voltage. Brownouts often occur during summer months when energy use is high.

Buck and Boost
A proprietary voltage regulation process used when an overvoltage or undervoltage situation occurs in the UPS. Undervoltage is boosted to make the voltage greater, and overvoltage is bucked to reduce it. The result is less reliance on the UPS battery, extending overall battery life.

Bus Voltage
The actual voltage supplied to the load as measured at the bus bars.

Provides flexible “plug and play” power distribution for a variety of applications where change and adaptation are important.


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.

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Symbol for ampere-hour capacity of a battery at the 10-hour discharge rate, to a specified end voltage.

Cable Managers
An easily installed device used to manage and protect cables either horizontally or vertically. Vertical managers are available as single- or double-sided, and for the full height of the rack.

Cable managers

Modular wall systems that can be used to partition white space environments, particularly in a colocation or multi-tenant data center (MTDC).


Canadian Standards Association (CSA)
An independent Canadian organization that tests for public safety, similar to the function of Underwriters Laboratories (UL) in the U.S.

An electronic component that can store an electrical charge on conductive plates.

Conformite Europeene (European Conformity)

Circuit Breaker (CB)
A device for manually opening (breaking) or closing a circuit to interrupt or apply electric power to an electrical apparatus. A circuit breaker can also open a circuit automatically when it senses an overload.

An electronic component in a UPS that provides regulated DC voltage to recharge batteries.

A structure, usually vertical, containing a passage or flue by which hot air is extracted out of an enclosure.

Clean Power
Electrical power which has been conditioned and/or regulated to remove electrical noise from the output power.

Cloud Computing
Internet- (cloud-) based development and use of computer technology. This new supplement, consumption and delivery model for IT services typically involves the provision of dynamically scalable, and often virtualized, resources as a service over the Internet.

Common Mode Noise
An undesirable voltage that appears between the power conductors and ground.

Commercial Power
The power supplied by local utility companies which can vary drastically in quality throughout the U.S. depending on location, weather and other factors.

Communication Bay
Also known as an option slot, a UPS feature that enables the addition of various connectivity cards for Web, SNMP, Modbus or serial connectivity interface capabilities.

Communication Bay
Eaton 9130 equipped with a communication bay.

Configuration file
The information or data loaded into and the supervisory module that controls the behavior of a power system to suit the particular requirements of a customer's site or installation.

Configurations Database
This is the total set of configurable parameters.

Conformite Europeene (European Conformity)
CE marking is used to signify that a product complies with all the applicable performance and safety standards adopted by the members of the European Union and is therefore certified for sale in European Union countries.

Converged Infrastructure
The combination of server, storage, networking, virtualization and sometimes other resources into an integrated solution that is managed as a whole rather than through separate management systems.

A device that delivers DC power when energized by a DC source. It’s also a section of a switching power supply that performs the actual power conversion and final rectification.

Crest Factor
Usually refers to current. It’s the mathematical relationship between RMS and peak current. A normal resistive load will have a crest factor of 1.4142, which is the normal relationship between peak and RMS current. A typical PC will have a crest factor of 3.

Critical Equipment
Equipment such as computers, communications systems or electronic process controls, which must be continuously available.

Amount of electricity that flows through a conductor, such as a wire.

Current Share
A process used to balance output currents between rectifiers. See Active Current Share.

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Direct Current

DC Distribution (DCD)
A module in a DC power system that distributes DC power to the loads. It also provides protection for the load cables.

DC Distribution - Fused version (DCF)
A DC Distribution module that uses fuses for protection.

DC Distribution - Miniature Circuit Breaker (MCB) version (DCM)
A DC Distribution module that uses miniature circuit breakers for protection.

DC Power System
An AC to DC power supply with integrated control and monitoring, and standby batteries designed to supply no-break DC power (usually 24V or 48V) to telecommunications and IT network equipment.

Delta Connection
A circuit formed by connecting three electrical devices in series to form a closed loop; most often used in three-phase connections. If you fly Delta Airlines, this most likely takes place in Atlanta, Salt Lake City or Cincinnati.

A reduction of some operating parameters to compensate for a change in one or more other parameters. In power systems, the output power rating is generally reduced at elevated temperatures.

Digital Input
An input which recognizes an open-circuit and short-circuit.

Digital Output
A voltage free relay contact.

Direct Current (DC)
An electric current in which the flow of electrons is in one direction, such as supplied by a battery.

Double Conversion
A UPS design in which the primary power path consists of a rectifier and inverter. It isolates the output power from all input anomalies such as low voltage surges and frequency variations.

DowntimeUse Eaton’s Downtime Calculator to quantify the impact
The time during which a functional unit can’t be used because of a fault within it or the environment.

Dry Contacts
Dry contact refers to a contact of a relay which does not make or break a current.

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The ratio of output to input power. Generally measured at full-load and nominal line conditions. If the power efficiency of a device is 90 percent, you get back 90 watts for every 100 you put in, and the rest is mainly dissipated as heat from the filtration process. To think of it another way, this would be equivalent to a bartender pouring off about an ounce and a half of your beer before handing you the remaining 14.5 ounces!

Electrical Line Noise
Radio frequency interference (RFI), electromagnetic interference (EMI) and other voltage or frequency disturbances.

Electromagnetic Interference (EMI)
Electrical interference that can cause equipment to work improperly, EMI can be separated into conducted EMI (interference conducted through cables out of the UPS) and radiated EMI (interference conducted through the air).

Electro Magnetic Compatibility.

Emergency Shutdown
Used to instantly or quickly shutdown all of the electrical power available to the UPS and the load. An emergency shutdown device is usually used during a crisis to prevent damage to the UPS and the load. Some computer-room installations require a Remote Emergency Power Off (REPO) capability as part of their security/safety system.

Energy Saver System (ESS)Read more here
Innovative technology from Eaton that enables select UPS models to operate at 99 percent efficiency without compromising reliability—not to be confused with inferior “eco” modes.

Energy Saver System (ESS)
Eaton Energy Saver System

Environmental rack monitoring (ERM)
This device continuously monitors environmental conditions at the rack level, providing an extra level of security for critical assets. It’s most often found in high-density data centers and applications like healthcare, where the environment must be maintained within acceptable levels.

Environmental rack monitoring (ERM)

ePDURead more here
A power distribution unit that mounts to rack enclosures and distributes power to connected devices via a wide variety of output receptacles.

This is the process of increasing the Float Voltage to the Equalize Voltage to recharge or equalize the batteries.

An alarm activation or de-activation.

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Fast Charge
Increasing the Operating Voltage after a battery discharge, following an AC failure, to give a rapid battery recharge.

Fault Tolerance
The ability of a system to continue operating in the event of a fault.

Federal Communications Commission (FCC)
A U.S. federal regulating body whose new EMI limitations are affecting the design and production of digital electronics systems and their related subassemblies.

A method of removing noise from the output of a UPS preventing "dirty power" from reaching connected equipment.

Float Voltage
The set output voltage of the DC power system (not including temperature compensation or other adjustments).

Flooded Batteries
A form of battery where the plates are completely immersed in a liquid electrolyte.

The number of complete cycles of AC voltage that occur during one second (Hz). In North America, electrical current is supplied mainly at 60 Hz, or 60 cycles per second.

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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Graphic User Interface (GUI)
A computer system using graphics images on the screen rather than text to display applications information for the user. As used in the Power Manager software.

Green Field
A new data center with many possibilities for sustainable and energy-efficient designs.

Ground (GND)
A conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to the earth, or to some conducting body of relatively large extent that serves in its place.

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Hardware Default Voltage
The rectifier output fail-safe operating voltage used if the rectifier microprocessor fails.

Describes any equipment connected to its power source by hardware attached directly to terminal blocks or distribution panels.

HarmonicsView this slideshow to learn more
sinusoidal component of an AC voltage that’s multiple of the fundamental waveform frequency. Certain harmonic patterns may cause equipment problems.

Harmonic Distortion
Regularly appearing distortion of the sine wave which is converted into a complex waveform at a multiple of the fundamental frequency.

Hertz (Hz)
A unit of frequency equal to one cycle per second.

Heterogeneous Network
A network with a multitude of workstations, and operating systems, and a variety of application types from different vendors.

High Efficiency Mode
A mode of UPS operation that cuts energy usage and operating costs..

High Rupturing Capacity (HRC) (fuse)
A precisely rated fuse which will operate under high fault current conditions, without self-destructing.

High Voltage (HV)
In the context of UPS products, high voltage is anything ≥200V: 200V, 208V, 220V, 230V, 240V, 250V, 480V and 600V.

High Voltage Spike
Rapid voltage peaks up to 6,000 volts.

Homogeneous Network
A network of components - workstation, server, operating system from the same vendor, or compatible equipment that can run under the same network or operating system.

Hot Swappable
The ability to change a module without taking the critical load off the UPS. Also see “user replaceable.”

Hot Swappable
The batteries on this Eaton 9130 UPS are hot swappable. Go to top



The total opposition to alternating current flow in an electrical circuit.

Input Line Cord
The covered bundle of wiring connected to the input terminals of the UPS. The end of the cord not connected to the UPS is connected, via an input plug, to an AC utility outlet supplying power to the UPS.

Input Plug
Connected to the end of the input line cord. To be plugged into an AC utility outlet receptacle.

Input Voltage Range
The voltage range within which a UPS operates in “normal” mode and doesn’t require battery power.

Inrush Current
The maximum, instantaneous input current drawn by an electrical device when first turned on. Some electrical devices draw several times their normal full-load current when initially energized.

Insulated Gate Bipolar Transistor (IGBT)
A three-terminal power semiconductor device, noted for high efficiency and fast switching. It switches electric power in many modern appliances such as electric cars, trains and UPSs.

Internal Bypass
UPS circuitry which provides a redundant power path. If there is an internal UPS fault, the connected load will still be supplied with unconditioned utility power.

UPS assembly that converts internal DC power to output AC power to run the user’s equipment. When the inverter is supporting 100 percent of the load at all times, as with an online UPS, there is no break from utility to battery power.

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 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.

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Kilovolt Ampere (kVA)
A common measurement of equipment capacity equalling 1000 volt-amperes. An approximation of available power in an AC system that does not take the power factor into account.

Kinetic Energy
The energy an object possesses because of its motion.

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Liquid Crystal Display

Light Emitting Diodes located on the front of the UPS that inform users of various power conditions and UPS operations.

Line Conditioner
A device intended to improve the quality of the power that’s delivered to electrical load equipment. A line conditioner is generally designed to improve power quality (e.g., proper voltage level, noise suppression, transient impulse protection, etc.).

Line Interactive
An offline UPS topology in which the system interacts with the utility line to regulate the power to the load. Provides better protection than a standby system but isn’t as fully prepared against irregularities as a full double-conversion system.

Linear Load
AC electrical loads where the voltage and current waveforms are sinusoidal. The current at any time is proportional to voltage.

The equipment connected to and protected by a UPS.

Load Bus
The bus to which the Load equipment is connected.

Load Segment
UPS configuration with separate receptacle groups, enabling scheduled shutdowns and maximum backup power time for critical devices.

Load Segment
This Eaton 9130 UPS is equipped with two load segments, each with three 5-15R.

Load Shedding
The ability to selectively shut off a set of UPS output receptacles, extending the capacity of the UPS battery. Some 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.

Low Voltage (LV)
In the context of UPS products, low voltage is anything <200V (100V and 120V).

Low Voltage Disconnect (LVD)
A module in the power system that disconnects the load from the batteries from the when the battery voltage falls below a preset value. The LVD reconnects the load to the batteries when the battery voltage rises above a preset value.

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Maintenance Bypass
An external wiring path to which the load can be transferred to upgrade or perform service on the UPS without powering down the load.

Operational sequence of a switch or relay where the new connection is made prior to disconnecting the existing connection, that’s also know as soft-load-transfer switching.

Management Information Base (MIB)
The structure of the database in an Eaton power system.

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.

The process of assigning physical entities to logical entities, e.g. when a particular analogue channel (internal or external) is assigned to be the channel used for measuring the bus voltage.

Maximum System Current
The maximum current that can be supplied by from a Power System (excluding batteries) under all conditions. Normally 120% of Rated System Current.

Miniature Circuit Breaker. A precisely rated, resettable circuit protection device.

A serial communications protocol that’s the most commonly available means of connecting industrial electronic devices. It allows for communication between many devices connected to the same network.

Metal Oxide Varistor. A non-linear semiconductor device used for surge protection or voltage limiting.

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National Electrical Code (NEC)
The code of standards and practices for the U.S. electrical and electronics industry. Developed by the National Fire Protection Association of Quincy, Mass. First published in 1896.

Network Transient Protector
UPS feature that isolates networks, modems and cables from power threats, including surges and spikes.

(1) A disturbance that affects a signal; it can distort the information carried by it.
(2) Random variations of one or more characteristics of any entity, such as voltage, current or data.
(3) Loosely, any disturbance tending to interfere with normal operation of a device.

Nominal Output Voltage
The intended, ideal voltage of any given output.

Nominal System Voltage
The DC output voltage generally used to describe a type of system, usually 24 V or 48 V.

Nominal Value
A designated value which 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.

Non-linear Load
AC electrical loads where the current is not proportional to the voltage. Non-linear loads often generate harmonics in the current waveform that lead to distortion of the voltage waveform.

Null Modem Cable
A special cable for connecting two RS-232 ports or devices directly, in place of a modem connection.

N+X UPS Redundancy
This form of redundancy provides reliable UPS operation by eliminating any single point of failure within the UPS.

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Any UPS that doesn’t fit the definition of online. Line-interactive and standby topologies are offline.

The unit of measurement for electrical resistance or opposition to current flow.

Ohm's Law
The voltage (E) is equal to the current (I) times the resistance (R). The formula is written: E=IR.

A UPS that provides power to the load from its inverter 100 percent of the time, regulating BOTH voltage and frequency, usually using double-conversion topology.

Orderly Shutdown
The sequenced shutdown of units comprising a computer system to prevent damage to it and subsequent corruption or loss of data.

Any point on a wiring system where current is taken to supply electrical power for a load.

Output Enable Delay
The delay between the start of primary side switching and the start of output current walk in. This is in two parts: a fixed hardware delay controlled by the secondary side control circuits and an adjustable delay controlled by the microprocessor. During this period the output voltage is at the minimum of approximately 40 V.

Output Waveform (UPS)
The shape of the graph of alternating current on the output side of a UPS. The highest quality of an output waveform from a UPS is the sine wave, but, some UPSs provide step waves or modified sine waves.

Output Waveform (UPS)

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.

Overvoltage Shutdown (OVSD)
A protection method that will shutdown any rectifier module with an output voltage over a preset maximum value.

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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.

Parallel Operation
The ability of UPSs to be connected so the current from corresponding outputs can be combined into a single load.

A logical division of a hard disk created to have different operating systems on the same hard disk or to create the appearance of having separate hard drives for file management, multiple users, or other purposes.

Peak Demand
The highest 15- or 30-minute demand recorded during a 12-month period.

The time relationship between current and voltage in AC circuits.

Plenum Cable
Cable that’s laid in the plenum spaces of buildings to facilitate air circulation for heating and air conditioning systems. The plenum space is typically used to house computer and telephone network communication cables. Cable that runs between floors in non-plenum areas is rated as riser cable.

Plug and Play
An electrical device that doesn’t require extensive setup to operate.

Plug and Play
The Eaton 3S UPS has plug and-play capability.

Power Factor (PF)
(1) The ratio of real power to apparent power. Watts divided by VA. Most power supplies used in communication and computer equipment have a power factor of 0.9.

(PF = 0.9)
VA x PF = W

Power Management Software
Provides monitoring and shutdown for UPS and connected load.

Power Sag
Low voltage (below nominal 120 volts).

Power Surge
High voltage (above nominal 120 volts).

Power System
A rack module, single rack or several parallel connected racks, providing DC power to a single DC bus.

Preset Voltage
The voltage that a rectifier will default to if communications with the Supervisory Module is lost. Generally, this is set to the float voltage by the Supervisory Module.

Public Switched Telephone Network

Pulse Width Modulation (PWM)
A circuit used in switching regulated power supplies where the switching frequency is held constant and the width of the power pulse is varied, controlling both lines and load changes with minimal dissipation.

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Ability to mount an electrical assembly into a standardized rack. Generally stacked up to 42U and 19 inches wide.

Rack Unit (U)
A unit of height measurement in a rack enclosure. A U is equivalent to 1.75 inches.

Rack Unit (U)
The Eaton 5PX UPS occupies 2U of rack space and the optional extended battery module also occupies 2U.

Rail Kit
A set of metal brackets that allows the installation of a UPS or extended battery module in a 2- or 4-post rack.

Rail Kit

Rated Rectifier Current
The maximum output current of a rectifier at 58V for a 48 V (nominal) rectifier, or 29 V for a 24 V (nominal) rectifier.

Rated System Current
The sum of the rated rectifier currents in the Eaton power system.

Raw Power
Electrical power which may or may not contain unwanted electrical signals.

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.

A UPS component that converts incoming AC power to DC power for feeding the inverter and charging the battery.

Rectifier Bus
The bus to which the outputs of the rectifiers are connected.

Rectifier Magazine (RM)
A module in the DC power system used to connect the rectifiers in the power system.

Rectifier Voltage
The voltage to which the rectifiers are set. This is assumed to be the same for each rectifier and does not include current share adjustments.

The ability to connect units in parallel so if one fails the other(s) will provide continual power to the load. This mode is used in systems when power failure can’t be tolerated.

A method of limiting voltage to a narrow range.

Relay Communication
Communication between a UPS and a computer through the opening and closing of solid-state relays that are pre-defined to indicate UPS status.

Battery time remaining to end of discharge

Radio Frequency Interference

Rectifier Magazine

Root Mean Square (RMS)
A modified average. Averaging a sine wave would give a zero, so to obtain meaningful values, the wave is first squared (S), then averaged over one period (M) and finally the square root taken (R). In a sine wave, the factor between RMS and peak is the square root of two.

The standard for serial interfaces (serial refers to the eight bits of each character successively sent down one wire) used by most computers, modems and printers.

A common point-to-point hardware configuration for serial communications.

A multidrop hardware configuration for serial communications. There is no intrinsic method of bus collision detection in RS-485, so higher layers in the protocol stack must take this into account.

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Scalable UPS
A UPS that allows for expandability; for example, enables a UPS to accommodate a larger load by purchasing additional power modules.

Simple Network Management Protocol (SNMP)
A User Datagram Protocol (UDP)-based network protocol. It’s used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention.

Sine Wave
A mathematical function that plots three qualities of an electrical signal over time: amplitude, frequency and phase. Clean, uninterrupted power is represented by a sine waves, which can also resemble ocean waves, though they're rarely perfect.

Single Phase (1Ø)Read more here
Power system with one primary waveform. Lower-capacity distribution of power using only one portion of a power source that’s three-phase, like what's supplied by most electric utilities. Used for heating and lighting, no large motors or other heavy-drain devices.


Sliding Demand
Calculating average demand by averaging demand over several successive time intervals, advancing one interval at a time.

Slope Discrimination Method
A scheme that causes the Overvoltage Shutdown set point to fall with increasing load.

Simple Network Management Protocol

Split-phase UPS
A UPS with two output phases referenced to a neutral connection with a specific phase displacement between phases, which allows flexibility in load configuration while maintaining the availability of bypass. A split-phase UPS can provide 120V and 208V on the output simultaneously without the use of an external transformer. The capabilities for output are:

  • Phase to neutral 100, 110, 120 or 127 Vac
  • Phase to phase 200, 208, 220, 230, 240 Vac

Square Wave
Output waveform generated by very basic, low-cost UPSs. Functions adequately for less sensitive loads, but may not provide acceptable quality input for some types of electronic equipment.

UPS type that "stands by," waiting for a power problem from the utility company and rapidly switching to UPS battery power to protect equipment against power failures, sags and surges.

Enables user to power up UPS in the absence of utility power.

Start Up Delay
The interval between power on and the start of current walk in. It is the sum of the Primary Enable Delay and the fixed and adjustable portions of the Output Enable Delay.

Static Switch
An electrical component in a UPS that turns power flow on and off on command without moving or mechanical components.

Status LEDs
Light Emitting Diodes (LEDs) that show the status of the UPS when they light up or turn off.

Step Load
An instantaneous change in the loading conditions presented to the output of a UPS

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.

Supervisory Module
The module that monitors and controls the operation of the DC power system.

A transient (or momentary) wave of current, potential, or power in an electric circuit.

Switching Frequency
The rate at which the source voltage is switched in a switching regulator or chopped in a DC-to-DC converter.

System Voltage
The nominal voltage of the power system, equal to the nominal voltage of the rectifier modules. 48 V or 24 V.

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Technischer Uberwachungs-Verein (TUV)
An independent non-profit organization that tests and certifies electrical equipment for public safety in the U.S. and worldwide.

Temperature Compensation
Adjustment of the rectifier output voltage to provide the optimum charging voltage for the battery. One of the components in system voltage control, calculated by the Supervisory Module calculation based on battery temperature.

Temperature Sensor
A sensor that is used to produce a variable electrical output representing the temperature of a component, typically a battery.

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.

A connector for attaching a conductor to an electrical apparatus.

Thermal Regulation
Monitoring the temperature of the batteries to ensure proper charging.

Three Phase (3Ø)Read more here
Power supplied through at least three wires, each carrying power from a common generator but offset in its cycle from the other two. Used for heavy-duty applications.


Topology (UPS)
The core technology of a UPS. Typically, a UPS is either standby, line interactive or online though other hybrid technologies have been introduced.

Total Harmonic Distortion (THD)
How much the circuit voltage deviates from a perfect sine wave. When viewed on a meter, a poor voltage THD is most often manifested in a flat-topped waveform that comes from the inability of a power source to respond to the demands of highly nonlinear loads.

Transfer Switch
A switch which will transfer current from one circuit path to another without interrupting the flow of the current.

Transfer Time
The length of time it takes a UPS to transfer to battery power. Typically measured in milliseconds (ms).

Transformer (T)
A magnetic device that converts AC voltages to AC voltages at any level. An ideal transformer is a lossless device in which no energy is stored that requires no magnetic current.

A temporary and brief change in a given parameter, typically associated with input voltage or output loading parameters.

Trickle Charge
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
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.

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Unbalanced Load
An AC power system using more than two wires, where the current is not equal due to an uneven loading of the phases.

Underwriters Laboratories (UL)
An independent non-profit organization that tests for public safety in the U.S. UL recognition is required for equipment used in some applications.

Uninterruptible Power System (UPS)
(1) An electrical system designed to provide instant, transient-free backup power during power failure or fault. Some UPSs also filter and/or regulate utility power (line conditioning).
(2) A Device whose sole purpose is to save your equipment, your data and your job.

UPS Topology
Overall term describing the internal circuitry of a UPS. There are three basic UPS topologies: standby (off-line), line-interactive, and online.

User Replaceable
Capable of being replaced by an end user. Connected equipment may need to be shut down first. Also see “hot swappable.”

User-Replaceable Batteries
User replaceable batteries allow the user to easily exchange UPS batteries, once the unit has been turned off.

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Variable Module Management System (VMMS)
Innovative technology from Eaton that maximizes UPS efficiencies at low load levels while supplying the load with continuous double-conversion power.

The creation of a virtual (rather than actual) version of something, such as an operating system, server, storage device or network resource. Operating system virtualization is the use of software to allow a piece of hardware to run multiple operating system images at the same time.

Volt/Voltage (V)
Electrical pressure that pushes current through a circuit. High voltage in a computer circuit is represented by 1, while low (or zero) voltage is represented by 0.

Volt Amps (VA)
The voltage applied to a given piece of equipment, multiplied by the current it draws. Not to be confused with watts, which are similar but represent the actual power drawn by the equipment, and can be somewhat lower than the VA rating.

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The time that the rectifier takes to reach rated output current after the Start Up Delay. The slope is fixed so that a lower output current will have a shorter walk in period.

The process of gradually ramping up rectifier output voltage (and current) at start up to prevent a large input current surge.

Watts (W)
The measure of real power. It’s the rate of doing electrical work. W x 1.3 = VA.

Wye Connection
A connection of three components made in such a manner that one end of each component is connected. It’s generally used to connect devices to a three-phase power system.