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| Uninterruptible Power Supply (UPS) Glossary |
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An extensive and comprehensive UPS Glossary, which describes UPS and related Power
Quality and Protection terms.The entries provide detailed account about the main meaning
and use of the term , its application, along with clarifying examples..
Quality and Protection terms.The entries provide detailed account about the main meaning
and use of the term , its application, along with clarifying examples..
DCE (Data Center Efficiency) - An efficiency metric, derived by dividing Total IT equipment
power by total Data center power. More information, see PUE, the reciprocal of DCE.
DC UPS: An Electronic device connected between the Utility Power (or alternate AC source)
and electric consumers, comprising of a DC Power Supply ( Rectifier), and Battery. The DC
UPS is intended to provide uninterrupted conditioned DC voltage, within strict regulation limits
against any Utility Power disturbances including outages.
Delta Conversion UPS : Hybrid type UPS offered by APC corporation. It uses an AC/DC
converter between the AC input and the DC battery buss. The converter is able to add or
subtract energy from the mains in order to stabilize output voltage and correct input power
factor. An output converter is connected between UPS output and battery. It acts as an ac/dc
rectifier to charge the batteries and as a dc/ac inverter upon mains outage.
Display: LCD or Led display, generally located on the UPS front, providing information about
the UPS status, including voltages, currents frequency etc. The display is also used in certain
systems to program system settings.
Dip: See Sag.
Double Conversion: Topology of On-Line UPS (VFI class per IEC 62040-3). The AC mains
voltage is converted to DC by means of an ac to DC Rectifier (or Charger), The DC voltage is
then converted to conditioned AC by means of the Inverter.
Dry contacts: Isolated relay contacts generally used for alarm or status signalization.
Dual Source UPS: Also called Dual input. UPS with separate Bypass input, enabling AC input
redundancy by feeding the rectifier and the by pass from different sources. UPS output will
automatically synchronize with the bypass input source.
Dynamic Regulation: System's output voltage deviation caused by connecting or
disconnecting rated load. Generally, different values refer to linear and non-linear type loads.
Earth fault: Leakage or short circuit to ground (Chassis) from isolated battery, isolated input
or output power lines, including Neutral. Some standards require activation of earth fault alarm,
if the earth fault current exceeds a rated value.
Earthing system: System for earthing of exposed conductive parts and neutral: IT system:
Neutral Isolated from earth (or high impedance to earth), exposed parts earthed Individually.
TN system: Exposed conductive parts connected to earthed Neutral.
TT System: Exposed conductive parts and Neutral are directly earthed.
ECO mode: An economical mode of operation, which enables certain On-Line UPS systems to
work in an Off-Line mode from the Utility, while the inverter, which is in hot standby operation,
is able to accept load upon mains failure.
Effective value: Effective voltage or current. See RMS.
Efficiency: UPS efficiency is defined as AC output Watts divided by AC Input Watts. The
full load efficiency of Standby or Line Interactive UPS is generally within 95% to 98%, and
within 90% to 95% for an Online Dual conversion system. Full load Efficiency is defined as
the ratio between stated UPS output Watts (stated Volt -Ampere capacity times stated output
Power Factor) divided by input Power in Watts.
For AC to DC ( Output Watts to DC bus) efficiency, see Inverter Efficiency.
EIA (Electronics Industry association): Australian membership based association to assist
development of national Electronic Industry.
EIA 232: Former RS232, now EIA 232 is a Communication Standard for Serial signal
transmission between a computer and peripheral devices. The maximum distance is about 50
feet (16m). Generally, the connection is made between UPS to the computer by means of 9 or
25 pin D-Type connector (often using only three wires) directly, or through modem and
telephone line.
EIA 422: Former RS 422, now EIA 422 is a 4 wire Communication Standard for Serial signal
transmission between a computers and peripheral devices. The maximum distance is 4000 feet
(1200 m). One driver can be connected to up-to 10 receivers. .
EIA 485: Former RS 485, now EIA 485 is a 2-wire Communication Standard for Serial signal,
multi point transmission. The maximum distance is 4000 feet 1200m). The standard specifies
up to 32 drivers and 32 receivers on a single buss.
Electromechanical UPS : ( Also called: Rotary , Batteryless, or Flywheel UPS).
An electromechanical Uninterruptible Power Supply that generally consists of a motor-generator
and additional hardware which enables to supply short time energy by utilizing kinetic energy
stored in a flywheel. It is normally applied in high power installation, by supplying the ride-
through energy from primary power outage until backup generator kicks in . It offers higher
efficiencies due to standby mode of operation and high Reliability due to absence of batteries.
EMC (Electro-Magnetic Compatibility): The ability of equipment to perform its function without
causing or suffering unacceptable degradation due to Electromagnetic Interference to or from
other equipment in the same environment.
EMI (Electro Magnetic Interference): Electromagnetic disturbance, generated mainly by
switching circuits and devices, that interrupt, obstruct or degrade the limits of performance of
electric equipment.
ENV 50091 – European Standard, Equivalent to IEC 62040, published by Cenelec. See IEC
62040
End Voltage: See Battery End voltage.
EPO (Emergency Power Off) – A functional module in the UPS enabling manual UPS turn off
at emergency situation, like fire or safety hazards, while disabling all output voltages.
External Battery: A battery located outside the electronic cabinet. In certain cases, the
external battery is connected in addition to the internal battery for Backup time expansion.
Fault Clearing: The ability to isolate a short-circuited load branch, by tripping its circuit
breaker or fuse.
Ferroresonant UPS: A Usystem which implements output voltage stabilization, by means of a
special output transformer, utilizing the constant voltage characteristic of the transformers’
saturated iron core.
To eliminate the current drawn from the inverter by the magnetizing transformer, a capacitor is
added to form a parallel resonant LC filter, tuned to UPS frequency.
The ferroresonant method provides output isolation and harmonic filtering. The shortcomings
are, relatively low efficiency, increased weight and volume.
FET (Field Effect Transistor): A transistor in which the current between the power terminals is
controlled through the gate terminal by means of an electric field, drawing very low drive
power. It is used as high frequency switching element in low power UPS Inverters.
Float Charging: Constant voltage charging method. See also Float voltage.
Float Current: Current drawn by a charged battery in float charging regime.
Float Voltage: DC Voltage applied to the battery by the charger (or rectifier) in constant
voltage charging regime. The float voltage value at 25 degrees Celsius is generally 2.3V/cell for
Lead-Acid battery and 1.42V/cell for Nickel-Cadmium battery. To extend battery lifetime, the
float voltage should be adjusted (compensated) with temperature according to battery
manufacturers recommendation.
Flooded batteries: Wet electrolyte batteries. Checking and adding water through vent caps
should periodically maintain these batteries. These batteries have proven reliability of extended
20 to 30 years of operation. They require large floor space, and ventilation systems, which
generally limit location to dedicated battery rooms.
Flywheel UPS: Electromechanical Backup system using ride through energy stored in a
flywheel to backup load after power outage until local generator kicks in.
See Electro-mechanical UPS.
Free maintenance battery: See VRLA battery.
power by total Data center power. More information, see PUE, the reciprocal of DCE.
DC UPS: An Electronic device connected between the Utility Power (or alternate AC source)
and electric consumers, comprising of a DC Power Supply ( Rectifier), and Battery. The DC
UPS is intended to provide uninterrupted conditioned DC voltage, within strict regulation limits
against any Utility Power disturbances including outages.
Delta Conversion UPS : Hybrid type UPS offered by APC corporation. It uses an AC/DC
converter between the AC input and the DC battery buss. The converter is able to add or
subtract energy from the mains in order to stabilize output voltage and correct input power
factor. An output converter is connected between UPS output and battery. It acts as an ac/dc
rectifier to charge the batteries and as a dc/ac inverter upon mains outage.
Display: LCD or Led display, generally located on the UPS front, providing information about
the UPS status, including voltages, currents frequency etc. The display is also used in certain
systems to program system settings.
Dip: See Sag.
Double Conversion: Topology of On-Line UPS (VFI class per IEC 62040-3). The AC mains
voltage is converted to DC by means of an ac to DC Rectifier (or Charger), The DC voltage is
then converted to conditioned AC by means of the Inverter.
Dry contacts: Isolated relay contacts generally used for alarm or status signalization.
Dual Source UPS: Also called Dual input. UPS with separate Bypass input, enabling AC input
redundancy by feeding the rectifier and the by pass from different sources. UPS output will
automatically synchronize with the bypass input source.
Dynamic Regulation: System's output voltage deviation caused by connecting or
disconnecting rated load. Generally, different values refer to linear and non-linear type loads.
Earth fault: Leakage or short circuit to ground (Chassis) from isolated battery, isolated input
or output power lines, including Neutral. Some standards require activation of earth fault alarm,
if the earth fault current exceeds a rated value.
Earthing system: System for earthing of exposed conductive parts and neutral: IT system:
Neutral Isolated from earth (or high impedance to earth), exposed parts earthed Individually.
TN system: Exposed conductive parts connected to earthed Neutral.
TT System: Exposed conductive parts and Neutral are directly earthed.
ECO mode: An economical mode of operation, which enables certain On-Line UPS systems to
work in an Off-Line mode from the Utility, while the inverter, which is in hot standby operation,
is able to accept load upon mains failure.
Effective value: Effective voltage or current. See RMS.
Efficiency: UPS efficiency is defined as AC output Watts divided by AC Input Watts. The
full load efficiency of Standby or Line Interactive UPS is generally within 95% to 98%, and
within 90% to 95% for an Online Dual conversion system. Full load Efficiency is defined as
the ratio between stated UPS output Watts (stated Volt -Ampere capacity times stated output
Power Factor) divided by input Power in Watts.
For AC to DC ( Output Watts to DC bus) efficiency, see Inverter Efficiency.
EIA (Electronics Industry association): Australian membership based association to assist
development of national Electronic Industry.
EIA 232: Former RS232, now EIA 232 is a Communication Standard for Serial signal
transmission between a computer and peripheral devices. The maximum distance is about 50
feet (16m). Generally, the connection is made between UPS to the computer by means of 9 or
25 pin D-Type connector (often using only three wires) directly, or through modem and
telephone line.
EIA 422: Former RS 422, now EIA 422 is a 4 wire Communication Standard for Serial signal
transmission between a computers and peripheral devices. The maximum distance is 4000 feet
(1200 m). One driver can be connected to up-to 10 receivers. .
EIA 485: Former RS 485, now EIA 485 is a 2-wire Communication Standard for Serial signal,
multi point transmission. The maximum distance is 4000 feet 1200m). The standard specifies
up to 32 drivers and 32 receivers on a single buss.
Electromechanical UPS : ( Also called: Rotary , Batteryless, or Flywheel UPS).
An electromechanical Uninterruptible Power Supply that generally consists of a motor-generator
and additional hardware which enables to supply short time energy by utilizing kinetic energy
stored in a flywheel. It is normally applied in high power installation, by supplying the ride-
through energy from primary power outage until backup generator kicks in . It offers higher
efficiencies due to standby mode of operation and high Reliability due to absence of batteries.
EMC (Electro-Magnetic Compatibility): The ability of equipment to perform its function without
causing or suffering unacceptable degradation due to Electromagnetic Interference to or from
other equipment in the same environment.
EMI (Electro Magnetic Interference): Electromagnetic disturbance, generated mainly by
switching circuits and devices, that interrupt, obstruct or degrade the limits of performance of
electric equipment.
ENV 50091 – European Standard, Equivalent to IEC 62040, published by Cenelec. See IEC
62040
End Voltage: See Battery End voltage.
EPO (Emergency Power Off) – A functional module in the UPS enabling manual UPS turn off
at emergency situation, like fire or safety hazards, while disabling all output voltages.
External Battery: A battery located outside the electronic cabinet. In certain cases, the
external battery is connected in addition to the internal battery for Backup time expansion.
Fault Clearing: The ability to isolate a short-circuited load branch, by tripping its circuit
breaker or fuse.
Ferroresonant UPS: A Usystem which implements output voltage stabilization, by means of a
special output transformer, utilizing the constant voltage characteristic of the transformers’
saturated iron core.
To eliminate the current drawn from the inverter by the magnetizing transformer, a capacitor is
added to form a parallel resonant LC filter, tuned to UPS frequency.
The ferroresonant method provides output isolation and harmonic filtering. The shortcomings
are, relatively low efficiency, increased weight and volume.
FET (Field Effect Transistor): A transistor in which the current between the power terminals is
controlled through the gate terminal by means of an electric field, drawing very low drive
power. It is used as high frequency switching element in low power UPS Inverters.
Float Charging: Constant voltage charging method. See also Float voltage.
Float Current: Current drawn by a charged battery in float charging regime.
Float Voltage: DC Voltage applied to the battery by the charger (or rectifier) in constant
voltage charging regime. The float voltage value at 25 degrees Celsius is generally 2.3V/cell for
Lead-Acid battery and 1.42V/cell for Nickel-Cadmium battery. To extend battery lifetime, the
float voltage should be adjusted (compensated) with temperature according to battery
manufacturers recommendation.
Flooded batteries: Wet electrolyte batteries. Checking and adding water through vent caps
should periodically maintain these batteries. These batteries have proven reliability of extended
20 to 30 years of operation. They require large floor space, and ventilation systems, which
generally limit location to dedicated battery rooms.
Flywheel UPS: Electromechanical Backup system using ride through energy stored in a
flywheel to backup load after power outage until local generator kicks in.
See Electro-mechanical UPS.
Free maintenance battery: See VRLA battery.
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