This lexicon explains central terms relating to uninterruptible power supplies, batteries, bypass, power quality, redundancy and standard designations in a uniform form.
A
Active standby mode
See Off-line UPS.
Installation height
Height of the installation location of a system above sea level. UPS systems are often designed as standard for operation up to 1000 m above sea level and ambient temperatures up to +40 °C. The cooling effect decreases at higher installation heights; This may require a reduction in the permissible ambient temperature or usable power.
Mean time between failures
Mean Time Between Failures (MTBF): statistical average of the failure-free operating time of a system. It is the reciprocal of the failure rate.
Failure rate
Probability per time interval that a system that was functional up to a point in time will fail in the following time interval.
Mean down time
Mean Down Time (MDT): average time from the failure of a system to the restoration of operational readiness.
Single-phase output
Designed for alternating current 230 V with phase, protective conductor and neutral conductor.
Three-phase output
Designed for three-phase 400 V with three phases, protective conductor and neutral conductor.
Output short-circuit current
Current that flows across the UPS output terminals in the event of a short circuit.
Output power
Active power that can be delivered to the output connections permanently or as a temporary overload. Apparent power and the minimum permissible power factor are usually specified.
Automatic Voltage Regulation (AVR)
Automatic voltage regulation. In UPS systems it is often done via electronics or relay-switched transformer windings. AVR extends the practically usable tolerance range of the input voltage beyond the usual standard tolerances.
Runtime
Minimum time for which a UPS supplies the connected load under specified operating conditions when the energy storage is fully charged in the event of a power failure.
Check runtime in the calculator: Play through load, reserve, battery status and suitable ERREPI shop entrances.
B
BAE
Battery connection unit.
Battery
In a UPS, the battery powers the inverter when the grid fails. Important design parameters are the desired backup time, power consumption of the inverter, intermediate circuit voltage, final discharge voltage and available charging voltage. Typical battery types are sealed, sealed and open batteries.
Battery capacity
The nominal capacity of a battery is the capacity that can be delivered at a defined discharge time, temperature, electrolyte density and final discharge voltage. In UPS applications, the removable capacity is often significantly lower than the nominal capacity due to short discharge times. Discharge performance curves from the manufacturer are required for dimensioning.
Closed batteries / low-maintenance
Batteries in which electrolyte fluid can be supplemented with distilled or demineralized water through openings in the battery housing. This type is sometimes also referred to as open.
Sealed batteries / maintenance-free
Batteries with a high rate of gas recombination that do not require refilling of water during their intended life. They are generally referred to as maintenance free.
Battery room
Space for larger battery systems in the building. Requirements for equipment and safety arise, among other things, from the relevant DIN-VDE regulations.
Battery low
Advance warning signal before the battery reaches its deep discharge limit.
Standby-redundant UPS
Redundant UPS, in which one or more UPS blocks are switched to standby and take over if an active block fails.
Continuous supply
Powering a load that maintains voltage and frequency within specified tolerances. Distortions and momentary interruptions must be within the limits permitted by the load.
Battery service life
Period of time during which a battery still has sufficient capacity for its task despite loss of capacity due to aging, storage and exposure to temperature. In UPS applications, the term nominal service life is often spoken of.
Blackout
Total power failure.
Lead-acid battery
Lead-acid battery with electrode plates and sulfuric acid as electrolyte. Lead batteries are often used as energy storage in UPS systems. A single cell has a nominal voltage of 2.0 V. A distinction is made between, among other things, low-maintenance and maintenance-free types.
Mimic diagram
Overview circuit diagram of function groups, partly used in operating displays.
Booster / booster stage
Additional voltage or voltage amplifier. In UPS systems, a booster can be used to increase the output voltage via electronic circuits.
Brownout
Short-term reduction in mains voltage.
Buck&Boost
Voltage conditioning that smoothes voltage peaks and voltage dips. If the voltage drops below a set value, the boost function increases it again; In the event of overvoltage, Buck reduces the voltage.
Bypass
Alternative current path that can bypass rectifiers and inverters. Depending on the system, it is used to switch to mains supply, maintenance or fault bridging.
C
CFR technology
Controlled Ferro Resonant Power UPS: UPS technology whose properties are determined by a regulated voltage stabilizer based on the ferroresonance principle.
Chopper
Literally chopper. In power electronics, a DC controller or part of a clocked rectifier that switches DC voltage and transforms or regulates it via other components.
Converter
Energy converter in the power circuit of a UPS.
Power factor
See power factor.
Crest factor
Ratio of the peak current to the effective value of the current. High peak currents are typical for power supplies. The total crest factor of connected consumers must not exceed the value specified in the UPS data sheet.
D
Continuous operation
Operating mode in which consumers are supplied via rectifiers and inverters during undisturbed network operation. Typical of online or double conversion UPS.
Float charge
See trickle charge.
DC UPS
Uninterruptible DC power supply. Compared to a classic UPS, the inverter for AC output is missing.
Delta converter
UPS technology with limited voltage conditioning and without complete frequency compensation. The term is used in the context of line interactive or delta conversion concepts.
DI box
Direct injection box. Transformer with galvanic isolation for coupling audio signals. Not UPS specific, but an example of galvanically isolated signal transmission.
Dual conversion / double conversion
Double conversion. Classic online UPS with separate power converters for rectification and alternation; corresponds to the real online UPS.
Dynamics
Quick readjustment of a system after changes such as load switching, so that specified initial values are achieved again.
Dynamic UPS
UPS, in which the load supply is realized using a rotating machine and an inverter. Opposite: static UPS.
E
Eco mode
Selectable energy saving circuit to improve the efficiency of UPS systems. It must be checked whether the operating mode matches the required security of supply.
Single-phase input
Designed for alternating current 230 V with phase, protective conductor and neutral conductor.
Three-phase input
Designed for three-phase 400 V with three phases, protective conductor and neutral conductor.
Standalone UPS
Standard term for a UPS that only contains one UPS block.
Single conversion
Single conversion. See reverse converter.
EMC
Electromagnetic compatibility. Electromagnetic interference is undesirable electrical influences that can influence or originate from the UPS and consumers. Filters and appropriate design limit these interferences.
Float charge
Charging voltage with which batteries are kept fully charged. Guideline values depend on battery type and temperature; Manufacturer information is relevant.
Backup power supply
Energy supply that replaces a mains supply in the event of a mains failure, for example UPS systems, emergency power systems or immediate standby units.
EUE
Energy switching device. See bypass.
F
Mean time between failures
Mean Time Between Failures (MTBF). See failure distance, average.
Cost of failure
Costs of preventing, discovering or correcting errors. These include contraception costs, testing costs and failure costs.
Ferro-resonant power UPS
UPS, the properties of which are determined by a magnetic voltage stabilizer based on the ferroresonance principle. Typical features are sinusoidal output voltage and short-term energy storage.
Hardwired connection
Electrical connection on terminals instead of via plug connection.
Filter circuit
Circuit with pass and stop band for frequencies. In UPS inverters, filter circuits reduce harmonics and radio interference in the output voltage.
Frequency accuracy
Inverter frequency accuracy. With self-clocking, it is typically much more precise than the mains frequency.
Frequency converter
Operation in which a UPS device converts the mains frequency, for example from 50 Hz to 60 Hz or vice versa. Not every device is suitable for this in every operating mode.
Radio interference
High-frequency interference with radio reception caused by unwanted electromagnetic vibrations.
G
Galvanic isolation
Separation of two circuits without a conductive connection. The transmission takes place, for example, via magnetic coupling in transformers or via optocouplers.
Noise level
See sound pressure level.
Rectifier
Power converter that generates direct current from alternating current. In UPS systems, it supplies the intermediate circuit, the inverter and the battery charge.
Rectifier 6-pulse
Rectifier circuit with typical harmonic content, which must be evaluated depending on the system and network conditions.
Rectifier 12-pulse
Rectifier circuit with reduced harmonic content compared to 6-pulse rectifiers.
Smoothing choke
Choke to reduce ripple in the DC circuit.
H
Half-load parallel operation
Parallel operation of two UPS blocks with the same power, in which each block carries part of the load during normal operation. If one block fails, the other takes over supply.
Semiconductor fuse
Very fast acting fuse to protect power semiconductors.
Hold time
See backup time.
Manual workaround
See maintenance bypass.
HE fashion
High Efficiency Mode: selectable energy saving circuit to improve the efficiency of UPS systems.
Boost converter / boost converter
Boost converter or DC/DC step-up circuit that boosts an output voltage above the input voltage.
Hot swap
Replacement of components, such as batteries, without interrupting the supply of connected consumers.
Height unit (U)
Unit of measurement for 19-inch devices. 1 U corresponds to 44.45 mm.
I
IEC 62040-3
Standard for classifying and evaluating the operational behavior of UPS systems.
IGBT
Insulated Gate Bipolar Transistor: modern power transistor that combines low drive power with favorable forward and switching properties.
induction
Transmission of electrical energy or signals via a magnetic field, for example in transformers.
Internal shutdown
Shutdown of the UPS when the deep discharge limit is reached. IT systems should be shut down in an orderly manner beforehand, usually via UPS software and interfaces.
Inverter
inverters; converts direct current into alternating current.
I²t value
Joule integral: Integral of the square of the current over a time interval. Relevant for thermal stress and fuse design.
J
Java
Programming language and runtime platform. Historically, Java was often used for operating system-independent management and service software.
K
capacity
See battery capacity.
Total harmonic distortion
Ratio of the rms value of all harmonics to the total rms value of the alternating voltage. Measure for the deviation from the ideal sine curve.
commutation
Transfer of current from one branch of a power converter to another. During the overlap time, both branches can carry current at the same time.
Contacts, potential-free
Configurable auxiliary contacts for user functions, electrically isolated from the monitored circuit.
Short circuit current
See output short circuit current.
L
Load factor
Ratio of the amount of electrical charge required for a full charge to the amount of charge previously removed. It describes the reciprocal charging efficiency.
UPS performance
See output power.
Load power factor
Ratio of active to apparent power at sinusoidal voltage.
Line conditioner
Device or function for compensating voltage fluctuations.
Line Interactive
UPS technology in which an inverter works in parallel with the supply network and charges the battery. New classification: VI.
Line-interactive UPS
Fuzzy older term for UPS systems with interactive mains operation. For precise classification, the IEC classification, for example VI, is more meaningful.
Load
Load or load resistance.
Load Power Factor
Power factor of the connected consumers or the load.
M
MDT
Mean Down Time. See Downtime, Medium.
Multi-block system
UPS system consisting of several blocks connected in parallel. A distinction is made between power parallel operation to increase the output power and redundancy parallel operation to increase operational reliability.
Follow-up operation
See Off-line UPS.
Modular structure
Modular design in which the power and runtime of a UPS can be expanded or adjusted.
Monitoring
Monitoring of a UPS system through integrated electronics, interfaces, event memory, remote monitoring or management software.
MTBF
Mean Time Between Failures: statistically determined mean time between two failures.
MTTR
Mean Time To Repair: average repair time.
N
NEA
Emergency power system. See emergency generator.
Rated power
Apparent power delivered by a UPS system under nominal conditions, usually in kVA.
Mains switch-back device (NRE)
See switching device.
Mains feedback
Unfavorable influences on alternating or three-phase networks due to non-sinusoidal or out-of-phase currents, for example harmonics of the rectifier.
Mains power
Power consumption of the UPS from the network. The shape of the curve depends, among other things, on the rectifier circuit and modulation.
Nonlinear load
Consumers whose impedance is dependent on current or voltage. They absorb non-sinusoidal currents, generate harmonics and can influence the shape of the voltage curve.
Emergency generator
System consisting of a motor and generator, often a diesel generator, to supply critical loads in the event of a prolonged power failure.
nnn / 111 to 333
IEC classification numeric code for UPS systems. It describes the dynamic output behavior when changing operating modes as well as during linear and non-linear load jumps. Code 111 is the cheapest class.
O
Harmonic
Sinusoidal component of a non-sinusoidal alternating variable with a frequency that is a multiple of the fundamental frequency. See also distortion factor.
Harmonic content
See harmonic distortion.
Offline UPS
UPS, in which consumers are supplied directly from the mains during undisturbed operation. In the event of a fault, the inverter takes over the supply from the battery. New classification: VFD.
Online UPS
UPS, in which consumers are already supplied during normal operation via rectifiers and inverters. In the event of a power failure, the supply comes from the battery without interruption. New classification: VFI.
Online permanent converter
UPS concept in which the mains voltage is permanently rectified and then converted back into a clean alternating voltage. New classification: VFI.
optocoupler
Component for galvanically isolated signal transmission via light.
P
Parallel systems
See multi-block system.
Phase control
Keeps the output voltage of a UPS in phase synchronization with the mains voltage. Important for low-interruption or uninterruptible switching to the bypass.
Pulse width modulation (PWM)
Method for generating a desired output voltage using switching pulses of different widths over time.
Pulse frequency
Frequency at which circuit breakers are switched in a power converter.
Pulse inverter
Inverter that converts direct voltage into alternating voltage through high-frequency switching. Filters reduce the switching frequency components and generate a sine-like output voltage.
PWM
Pulse Width Modulation. See pulse width modulation.
Q
Quality assurance
Organizational and technical measures with which a defined quality standard is achieved and maintained.
R
Rackmount
UPS system for installation in 19-inch racks.
Redundancy
Presence of more than one way to fulfill a required function.
Level of redundancy
Description of how many elements of a system are present redundantly and how many are required to fulfill the function.
Relay contacts
Switching contacts that can also switch higher voltages or currents. See also potential-free contacts.
Repair rate
Inverse value of the average downtime or repair time, depending on the model under consideration.
Rotating UPS
See dynamic UPS.
RPA - Redundant Parallel Architecture
Concept for fault-tolerant parallel connection of UPS systems, in which critical elements and functions are available redundantly.
RS232
Serial interface for data exchange between UPS and PC or server.
Feedback
See network feedback.
S
S
IEC classification abbreviation for sinusoidal output voltage with distortion less than 0.08. Other waveform abbreviations are X and Y.
Sound pressure level
Measure of the noise level of a UPS system, usually given in dB(A).
Phase imbalance capability
Ability of a three-phase system to supply phases with different loads.
Interfaces
Communication interfaces of a UPS, for example potential-free contacts, RS232, SNMP or RJ45.
Self-commutated converter
Power converter that does not require an external AC voltage source for commutation. Inverters in UPS systems are examples of self-commutated power converters.
SNMP
Simple Network Management Protocol. Protocol for monitoring and managing network devices, including UPS systems.
Voltage spikes
See transients.
UPS output voltage tolerance
Permissible deviation of the output voltage in static and dynamic operation. An important quality feature is the time in which a deviation caused by load surges is corrected.
spikes
Short-term voltage peaks. See transients.
Standby
Operating form of an off-line UPS.
Static UPS
UPS consisting of power converters, switches and batteries without a rotating machine. It is intended to ensure a constant supply in the event of a power failure and, if necessary, improve energy quality.
Static bypass
Electronic switching device, usually with thyristors, for the bypass branch.
Stress factor
Factors influencing the reliability of components, for example temperature, environment or electrical load.
Current limiting
Control technology limiting excessive currents to protect semiconductor components.
Power conditioner
Device or function for compensating voltage fluctuations. Also called line conditioner.
Converter
Device that converts direct current into alternating current or alternating current into direct current.
Crest factor
See crest factor.
Battery backup time
See backup time.
Surge protection
Surge protection or surge protection device.
Switching power supply
Clocked power supply with fast-switching transistors. Such consumers often absorb pulse-shaped currents.
Synchronization range
Tolerance range in which the inverter frequency can be synchronized with the grid frequency. Outside this range, the inverter operates independently and bypass operation may be restricted.
T
Switching frequency
Frequency at which a branch of a power converter circuit is periodically switched.
Partially parallel UPS
UPS with inverters working in parallel and a common battery, common rectifier or common rectifier combination.
Partially redundant UPS
UPS with redundancy for inverters or other components.
Thyristor switch
Electronic switch that is often used in the bypass branch of UPS systems and can switch loads very quickly to direct mains supply.
Total Harmonic Distortion (THD)
Total distortion caused by harmonics. See harmonic distortion.
Transients
Short-term overvoltages in the microsecond range, caused for example by short circuits, switching processes or lightning strikes.
Isolation transformer
Transformer for the galvanic isolation of two circuits.
U
Bypass
Standardized term for an alternative current path, which is now usually referred to as a bypass.
Reversible converter
Power converter concept that combines rectifier and inverter operation in one power converter. From a technical point of view, it must be carefully checked whether such a concept meets the requirements of a UPS.
Transfer switch
Device for switching consumers from the grid to the inverter or vice versa.
Transfer time
Time span between initiation and execution of a switchover.
Interruption time
Period of time during which the output voltage is below the permissible tolerance range. It is greater than the switching time and depends on the control.
UPS
Uninterruptible Power Supply, English name for UPS.
UPS
Uninterruptible power supply. Basic concepts are Off-line UPS (VFD), Line Interactive UPS (VI) and Online UPS (VFI).
UPS block
UPS unit with at least a rectifier, inverter, battery or other energy storage device that can be operated in parallel or redundantly with other blocks.
Backup time
Minimum amount of time the UPS will power the load from fully charged energy storage in the event of AC power failure.
Monitoring and diagnostic system
System for troubleshooting, event recording and monitoring of important UPS data such as voltages, currents, frequencies, powers and messages.
V
VBG 4
Historical accident prevention regulations for electrical systems and equipment. Today, current DGUV and VDE regulations must be observed.
Availability
Probability of finding a repairable system functional at any given time. Approximately: A = MTBF / (MTBF + MDT) if maintenance and logistics are not taken into account.
Power loss
Active power that is converted into heat in a component or device.
Power factor
See power factor.
Wear-out failure
Failure due to wear and tear. In practice, in static UPS systems this often affects mechanical parts such as fans.
VFD
Voltage and Frequency Dependent: IEC classification for UPS systems whose output depends on the voltage and frequency of the network.
VFI
Voltage and Frequency Independent: IEC classification for UPS systems whose output voltage and output frequency are independent of fluctuations on the input side.
VI
Voltage Independent: IEC classification for UPS systems in which the output voltage is stabilized while the output frequency follows the input frequency.
W
Maintenance bypass
Manual or mechanical bypass that allows a UPS to be removed from the load path for maintenance.
Inverter
Power converter that converts direct voltage into alternating voltage. In UPS systems, it generates the output voltage for the connected load.
Recharge time
Minimum time period required to fully charge discharged energy storage devices under specified operating conditions.
Efficiency
Ratio of output power to input power under specified operating conditions.
X
X
Abbreviation of the IEC classification for sinusoidal waveform with linear load, but with non-linear load with distortion greater than 0.08 or with restrictions to be observed by the manufacturer.
Y
Y
Abbreviation of the IEC classification for non-sinusoidal output voltage that can exceed limits according to IEC 61000-2-2.
Z
Random failure
Unforeseeable failure of a system or component without obvious prior notice. Appropriate operating conditions can reduce the likelihood.
Reliability
Quality benchmark that statistically describes the risk of failure of systems, devices or components. See MTBF.
Reliability calculation
Calculation or estimation of the service life and functional duration of electrical modules, devices or systems.
DC link
Connecting link between rectifier and inverter with smoothing and measuring device as well as battery connection.