Graceful Shut Down: Software function that shuts-down computers fed by the UPS, after mains
outage, a few minutes before it turns off due to battery discharge. Graceful shut
down resembles manual computer turn off, no data is lost and the computer reboots
Grounding: Connecting the UPS chassis to external protective ground.
Harmonics: A sinusoidal component of a periodic wave, having a frequency that is an integral
multiple of the fundamental source frequency.
High Frequency UPS: A term sometimes used for systems which utilize high frequency waveform
in the internal UPS inverter. Inverter switching is performed by high ultrasonic carrier frequency (
above 16 kHz) waveform, pulse width modulated with a sinusoidal system's output frequency
waveform. The carrier frequency is attenuated by Low pass filter to provide a sinusoidal 50 or 60
Hz output waveform. This technique is today standard in almost all Line Interactive and ON-Line
systems.
Hot standby operation: A standby mode of operation generally implemented in Series redundant
systems. The UPS is constantly fully operational and running without load. It starts to supply
current immediately upon load connection.
Hot Swappable modules: Battery modules or redundant modular sub-assemblies, which
can be replaced without turning the UPS off.
Hybrid UPS : Uninterruptible power supply that uses a DC to AC 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.
IEC: International Electrotechnical commission of standards. Many countries adopt IEC standards
as their national standards.
IEC 60529 (IP code): See IP Code.
IEC 61000-3-2: Standard- Limits of input current harmonics (equipments with Input Current <=
16A/Phase).
IEC 61000-3-4: Standard- Limits of input current harmonics (equipments with Input Current >
16A/Phase).
IEC 61000-4-11:Standard- Voltage dips, short interruptions and voltage variations immunity tests
(equipments with Input Current <= 16A/Phase).
IEC 61000-4-34:Standard- Voltage dips, short interruptions and voltage variations immunity tests
(equipments with Input Current > 16A/Phase).
IEC 60146-5: Standard - Switches for Uninterruptible Power Systems.
IEC 60950 (former IEC 950): Standard –safety of Information Technology equipment (Applicable
also to UPS systems).
IEC 62040-1-1: Standard -General and safety requirements for UPS systems used in restricted
access locations.
IEC 62040-1-2: Standard -General and safety requirements for UPS systems used in operator
access areas.
IEC 62040-2: Standard- UPS Electromagnetic compatibility (EMC) requirements.
IEC 62040-3: Standard- UPS performance requirements and test methods.
IGBT (Insulated Gate Bipolar Transistor): A transistor which combines FET input and
bipolar Transistor output, forming a switching device with very low drive power, high blocking
voltage, and low conduction losses. IGBT is the most popular power-switching element in UPS
inverters.
ITI (Information Technology Industry Council). Formerly known as CBEMA : Computer and
Business Equipment Manufacturer Association. ITI is a group of leading high tech companies in
the USA.
ITI Curve (CBEMA Curve): An AC input voltage envelope, published by ITI council, that shows
input voltage limits which typically can be tolerated ( will not cause functional interruption) by
most Information Technology Equipment.
According to ITI curve a computer will not turn off in short (less than 20 ms) power interruptions,
or in case of line voltage sags up to 70% of nominal lasting less than 0.5Second. The curve
describes also the influence of high input voltage on computer operation continuity.
Internal Battery: A battery located inside the UPS cabinet.
Interharmonics: Waveforms with frequencies, which are not integers of the fundamental source
frequency.
Input current distortion: The distortion of the AC input current due to harmonics. The
distortions are measured by means of input current THDI figure at the AC input of the UPS. Some
standards limit the maximum allowed input current distortions. Most systems today limit THDI
distortion to less than 10%.
Input voltage distortion: The distortion of the AC input voltage due to harmonics. The distortions
are measured by means of input voltage THD figure at the AC input of the UPS.
Inrush current: The initial current at the input of the UPS upon turn on (see Rectifier
walk-in). Also the initial current a consumer draws from the UPS upon turning on the consumer.
The inrush current is generally caused either, due to charging of DC filter capacitors, or because of
sub-cycle magnetizing current of a transformer, located in the turned on equipment.
Inverter: Functional UPS module that inverts the DC battery voltage to 50Hz or 60Hz AC voltage.
Inverter Efficiency: Also called AC to DC efficiency: AC Output Watts divided by
Inverter Input Watts, when load is connected to Inverter output. (Inverter input watts
equals DC buss voltage multiplied by the current drawn by the Inverter). Inverter efficiency is used
for calculating battery capacity. Ratings vary from 80% at low DC voltages to 95%, at high DC
buss voltages. Full Load Efficiency is defined as Rated Output Watts (Rated Volt-Ampere times
stated output power factor) divided by DC input Current times Nominal DC input Voltage.
IP Code: Degrees of Enclosure protection evaluated as described in IEC 60529 standard. The first
character of the IP code indicates protection degree against the ingress of solid objects. The
second character indicates protection against ingress of water. For example
IP 20 means: Protection against ingress of solid foreign objects of 12.5mm Diameter and greater,
whereas the second character indicates no protection against water. IP31 protects against ingress
of solid objects greater than 2.5mm Diameter and against vertically falling water drops.
ISO (International Organization for Standardization): ISO is a global International network that
Identifies, develops, and delivers standards required for business, government and society.
ISO 9001: A set of standards for quality management concerned with production and service
policies. ISO 9001 2000 has replaced the old ISO 9001, As well as ISO 9002 and ISO 9003 which
became discontinued.
Isolation: Generally refers to the allowed maximum KV ( Kilo-Volts) between input and ground,
output and ground and input to output in UPS systems with isolation transformer.
Isolation transformer: A transformer connected at the input of the UPS to isolate the battery
from the utility grid, or at the output of a UPS to isolate the load from the utility grid.
IT System: See Earthed System.
Lagging Power Factor: Power factor of an Inductive type circuit, in which the current
lags behind the source voltage (negative cos phi)
Lead Acid Battery: A rechargeable battery common in UPS systems, it is composed of
lead plates suspended in electrolyte solution of sulfuric acid and water.
Leading Power factor: Power factor of a capacitive type circuit, in which the current
leads the voltage (positive cos phi).
Line: See primary power.
Line Interactive UPS: A system, which energizes the load from the utility mains
providing conditioned power by filtering and stabilizing mains voltage (VI class per IEC 62040-3).
Upon mains outage the load is energized from batteries via the Inverter.
Linear Load: load comprised of linear (non switching) components, such as, resistors,
capacitors, inductors, motors, lamps, transformers etc.
LVD (Low Voltage Disconnect): A circuit or device that disconnects load from battery, when the
battery discharges below a minimum low voltage level (generally 1.75 V/cell for lead Acid batteries).
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| Comprehensive power UPS glossary |