Lexicon

PowerWalker Knowledge-Database

PowerWalker Lexicon

The following Lexicon is intended to help newcomers to the UPS-World better understand the whys and hows of UPS. Please be aware that this lexicon does not replace the official user manual and should be used as a companion guide and reference work. This page is sorted alphabetically.

A|B|C|D|E|F|G|H| I |J|K|L|M|N|O|P|Q|R|S|T|U|V|W|Y|X|Z

A

Active Power

A measure of actual power (Watts) drawn by an electrical load that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction. Also known as real power. 

AGM Batteries (Absorbent Glass Mat)

These batteries are a type of VRLA batteries that dont require constant maintenance. They feature fiberglass mesh between the battery plates which serves to contain the electrolyte and separate the plates.

Alternating Current (AC)

An electrical current whose electrons flow briefly in one direction to a peak before dropping back to zero and then, flowing in an alternative direction before repeating itself. The waveform created is a sine-wave.

Amp/ Amperes [A]

A measure of the flow of electrical current.

Ampere-hour [Ah]

A measure of the number of amps/ energy that a battery set can provide per hour within a 20 hour timelapse. This will also define the battery capacity.

APFC (Active Power Factor Correction)

Almost all modern PC and IT equipment are equipped with APFC power supplies (According to CE regulations, all power supplies over 80W must have an APFC function). The purpose of the APFC is to reduce reactive power, which is wasted energy. This makes the equipment more energy-efficient.

The drawback is that the APFC power supply requires higher energy at start-up. UPS without compatibility with APFC loads must be oversized. If not, they will certainly go in overload. 

Apparent Power

The total power drawn by a load at a given supply voltage measured in VA.

Automatic Bypass

An electrical circuit incorporated within a UPS (On-Line UPS) creating a power supply path which can be relay or static switch-based. It is used by the UPS to switch its load to the mains if it experiences an overload or internal failure.

ATS (Automatic Transfer Switch)

The ATS is designed with two independent power inlets to supply power to the load from primary power source. In the event of a significant loss of mains power, an automatic transfer switch will detect the power loss and transfer the load to the secondary supply line with a low transfer time.

AVR (Automatic Voltage Regulator)

A mains power supply voltage stabilisation mechanism. It regulates the voltage of the source (mains) before sending it to the load connected onto the UPS. The UPS switchs automatically to « AVR Mode » when sensing irregularities in the voltage range at the source. After a “Boost” (when the voltage is too low) or a “Buck” (when the voltage is too high), the regulated voltage will be sent to the load. This mechanism is part of a Line-Interactive UPS.

The AVR is designed to prevent damage to electrical equipment sensitive to voltage variations, such as domestic electrical equipment (TV, monitors, game consoles, audio/video equipment, telephony, etc.), prolonging their life.

Autonomy (Backup Time or Runtime)

Also known as back up or discharge time, battery autonomy is a measure of the time (minutes or hours) for which the battery will support the critical load during a mains failure. Autonomy is a function of battery charge state, capacity and load size.

Availability [%]

A ratio of system up-time compared to its downtime expressed as a percentage. It provides the probability of a system being operational at any given time during its working life.

Formula: Availability = Uptime/(Uptime + Downtime)

B

Battery Capacity

The greater the capacity, the more energy it can store. Water vs electricity analogy: The battery capacity can be compared to the space in a water bottle. If the water bottle is « bigger », then it can store more water (energy).

Battery capacity is measured in amp-hours [Ah]. Usually, a battery rated at 100Ah can deliver 5A over a 20-hour period at room temperature. The fraction of the stored capacity that a battery can deliver depends on multiple factors.

Battery Functionality

The way a battery works and reacts over its lifespan depend on many factors such as: load cycle, charge cycle, internal chemistry, current drain, and temperature.

Battery Configuration
  • Battery Cell: A simple electrical circuit within a battery block consisting of positive and negative electrodes or plates, an electrolyte and separator.
  • Battery Block: A self-contained battery consisting of a number of individual and connected battery cells.
  • Battery String: Comprises of a number of battery blocks arranged in series to achieve a set VDC and Ah rating.
  • Battery Set: Comprises of a battery string or a number of battery strings.
Battery Mode

Battery Mode is one of the characteristics that make the UPSs so useful. In case of an anomaly or failure, depending on your UPS technology, the UPS will trigger Battery Mode. The most known example is a Blackout.

When the UPS recognizes a failure at the source (mains), depending on the technology, it will switch to the reserves stored in the battery system connected to the UPS. These can be internal or external batteries.

Battery Pack

All external batteries that are not integrated into the UPS are called external battery modules (EBM) or battery packs. A battery pack is a compatible accessory to the UPS and they provide further Backup time if required. Contrary to external battery banks, battery packs are user-friendly to connect.

It is not allowed to connect too many in parallel. The internal charger of the UPS must be able to properly charge the connected battery packs. If you plan to connect more than two of them, please consult our support team in advance.

Please note that batteries used in the UPS and all battery packs should consist of the same quantity, type, and condition of batteries. Therefore it is not recommended to connect new battery pack to a UPS with old internal batteries (we recommend to replace internal batteries at the time when connecting a new battery pack). The recommendation is a best practice and not an obligatory action.

Battery Power

A battery with high-power can deliver its energy very quickly. Water vs electricity analogy: The battery power can be compared with the opening of a water bottle. If the opening is « bigger », then the water can flow out faster.

Blackouts

A total loss of electrical power (power supply failure), also referred to as an outage.

Bundle (Rack)

A bundle is made of these two products (example: UPS engine + EBM). A bundle is the engine and the EBM together. Please be aware that the packaging remains separated.

Bypass Mode

A secondary power path providing a power supply in case the primary one fails. In general, a current that goes from source directly to the load is called Bypass. All impurities from the source are not removed.

C

CE « European Conformity »

The CE or European conformity mark on a product indicates that the manufacturer or importer of that product affirms its compliance with the relevant EU legislation and the product may be sold anywhere in the European Economic Area (EEA). The CE mark affirms the goods conformity with European health, safety, and environmental protection standards.

Centralized Solution

The UPS becomes a demanding element of the electrical installation of a building, a project, or a plant. The final solution will certainly have sufficient backup time, will be a stable power source and will be part of the power network of a building or project. This solution protects entire building-complexes or parts of them.

Circuit Breaker

A protective component of the UPS that interrupts the flow of current when it exceeds a specific value. In the event of a high surge, the breaker will trip.

Charger

Component used to supply the battery with the electrical power (DC) required to recharge and/or float charge the battery. After the rectification (rectifier) of the AC to DC, the charger will turn the electrical energy into chemical energy in the Battery.

Crest Factor

Some loads, such as switching power supplies or lamp ballasts, have current waveforms that are not sinusoidal. They draw a high current (AKA In-rush currents) for a short period of time, and their crest factors, therefore, can be quite a bit higher (all electrical equipments should have a defined crest factor).

The graphical example shows current waveforms for two different loads, one sinusoidal (the blue wave) and one non-sinusoidal (the pink wave). Both have the same rms current, but as you can see, the crest factor is quite different. Depending on how high the crest factor is, the higher the peak.

Both loads draw the same amount of true power.

However, a UPS may not be able to provide the required peak currents that the non-sinusoidal load demands. When selecting the UPS to power a load, you would need to choose a UPS possible of supplying more than the peak current of the load. In order to determine whether or not the UPS can handle high crest factor peak currents, you can find the “crest factor” specifications in the datasheet. They refer to the crest factor that the UPS can work with (normally 3:1).

Current [A]

The ‘volume’ of electricity flowing in a circuit and expressed as Amps.

Current Limiting

The configuration of a circuit or system that maintains a current within its prescribed limits. UPS systems have an electrical current limiting that regulates the output current to a value within the UPS limits. Current limiting may occur when a load demanding high inrush current is turned on.

CVCF Mode (Converter Mode)

Only On-Line products have this mode. The UPS can set a specific desired frequency value for the connected Loads (the % of max. connected load will be derated). Be aware that if the UPS has a failure, it won’t transfer to Bypass mode, instead it will just shutdown.

D

DC UPS

This type of solution provides an efficient and energy-saving power protection. It has a one-time power consumption during the AC-DC conversion. The DC UPS are designed for widely-accepted commercial inputs and outputs standards, usually 12VDC or 5VDC. Typical applications is in telecommunication devices like routers, phones or alarm systems.

Decentralized Solution

The UPS ensures the availability of your mission-critical equipment and provides clean output power to your sensitive devices. They are used in targeted protection of selected loads and are within a household budget. The focus of this consideration is maximum flexibility and very good cost controlling by targeted protection of critical systems.

Deep Discharge

A battery charge state whereby the battery voltage (VDC), has dropped below a safe operating level from which it cannot recover. In a battery set of 12V (six battery cells with 2V each), the battery voltage should not go lower then 9,6V (1,6V per battery cell).

Deep Discharge Protection

A feature in the UPS that protects the batteries from deep discharging. Depending on the firmware and the load level on the UPS, if the UPS goes into Battery Mode and a defined voltage level is achieved (normally higher than the deep discharge level as precaution), the UPS will shutdown to protect the battery from deep discharging.

Dip

It is a reduction of AC voltage at a given frequency. Dips are usually caused by system faults, and are also often the result of switching on loads with heavy startup currents – also called sag.

Direct Current (DC)

Electric current, the electrons of which are flowing in one direction only. For example, stored power in a battery is DC.

Double-Conversion

A function employed by an On-Line UPS which feeds mains electricity into a rectifier/ charger, and converts AC to DC. The DC then charges the batteries and also feeds the DC into an inverter which then converts the DC back to AC. This clean power then feeds the electrical equipment. In the event of mains overvoltage or failure the UPS continues to supply the load from its battery with no transfer delay.

Dry Contact

Also known as volt-free contacts or potential-free contacts. It refers to a secondary set of contacts of a relay circuit which does not make or break the primary current being controlled by the relay. Usually, with a Dry-Out Contact, you can get a signal out off the UPS and automate external devices. A Dry-In Contact on the other hand, can send a signal in the UPS. For example, the possibility of turning the UPS on and off remotely.

The AS400 Cards (PowerWalker Management Cards) offer multiple Dry-Contacts to enhance the usability and the functionality of the UPS.

E

EAN & GTIN

The European Article Number (EAN) is a standard describing a barcode symbology and numbering system used in global trade to identify a specific retail product, in a specific packaging configuration, from a specific manufacturer.

The standard has been absorbed in the Global Trade Item Number (GTIN).

Earthing System

An earthing system connects the electric power system with the ground for safety and functional purposes. It may also play a role in the protection against fault currents.

ECO Mode

On-Line UPSs offer ECO mode, which significantly reduces their own power consumption. Naturally it comes at a cost. When running in ECO Mode, the UPS will in-fact run in Bypass Mode with adjustable limits. This means if the input voltage and frequency are within set limits (i.e., 49-51Hz and 220-250V), it will pass through the input voltage directly to the output. Once the voltage or frequency goes off the limit, it will switch to On-Line Mode. The drawback to consider in this setup is the transfer time between ECO Mode and On-Line Mode.

EBM (External Battery Module)

All external batteries that are not integrated into the UPS are called external battery modules (EBM) or battery packs. An EBM is a compatible accessory to the UPS and they provide further Backup time if required. Contrary to external battery banks, EBM are user-friendly to connect.

EBM-Auto Detection

The automatic detection of external battery modules allows you to plug & play battery packs without having to manually configure the UPS settings.

EPO (Emergency Power Off)

A signal contact on a UPS which will initiate a total UPS shutdown. Please be aware that it works like an emergency stop switch, to turn the UPS on again, you have to manually turn the device on.

External Battery Banks

Usually UPS higher than 3kVa can be connected with non-series batteries, also called external battery banks. These batteries have to be installed and connected by an electrician.

F

Fan Logic

The fan logic of the UPS is always managed by the firmware and cannot be changed. When the UPS is first-time plugged-in, it is charging batteries (not 100% full) or it is in any other mode, the fans will usually be on. All On-Line UPS have constant operating fans in any type of operation.

Floating Mode or Float Charging

Part of the Optimized Battery Management (OBM). A battery charging state used on UPS batteries, designed to maximise battery life. The voltage is maintaned constant and the battery will charge slower until the battery is full.

Flywheel

A device used to convert kinetic energy into a standby supply of DC power for the UPS either in place of a battery set or to reduce the initial discharge during momentary interruptions.

Form Factor

UPSs come in different forms (casing/ presentation). The most known are “Tower” and “Rack”.

  • Tower: are the most common type of UPS, known be every UPS user. They are mostly used when space is not a concern. All accessories are also, space needful.
  • Rack: this kind of UPS is best-used in a Rack-System. They come in a standard 19” width for every 19” racking system. The accessories for this kind of UPS are also formatted to work in a Rack-System.
  • Multi-Socket or Brick: many products in our household come in this format. That is why UPS products were also made in this format, to replace simpler products with the same shape or function, and give them a small edge over them with basic UPS functions.
  • Wall-Mountable: This type of UPS can also be wall-mounted or it can only be used as a wall-mounted solution.
  • Portable Device: This type of UPS is suitable for outdoor use.
  • Socket-Plug In: Small UPS devices that can be easily plugged in a compatible socket and are ready to use after the internal battery has charged.
Frequency

The frequency is defined by the number of complete cycles of a waveform or alternating current which repeats per unit of time, in this case measured in Hertz. In Europe, Africa, Australia, southern South America, most of Asia, and Russia, the frequency of the alternating current in household electrical outlets is 50 Hz, whereas in North America and northern South America, the frequency of the alternating current in household electrical outlets is 60 Hz.

Frequency Range

These ranges are the values in which the UPS can work with.

Frequency (Synchronized Range)

An On-Line UPS is designed to work in a double conversion technology. This means output frequency and voltage are isolated from input and generated by internal electronics from DC voltage. Nevertheless, you might notice that frequency (not the voltage) is changing within a small range. This effect is caused by intentional synchronizing of the output voltage to the input voltage.

As a benefit, whenever you switch between bypass and line mode, the synchronized will minimize transfer effect from one frequency level to another. As a drawback, the frequency is not fully stable, and follows the input frequency, which is not always is a desired outcome. In normal circumstances small changes within a narrow limit are causing no negative effect to the load. If you want to disable synchronization of the frequency, please turn on the CVCF Mode.

G

Generator

An equipment that uses combustion to generate mechanical energy, to provide an AC or DC power source.

Generator Compatible

UPS Models with this feature will not shutdown unexpectedly because of the frequency fluctuaction created by the connected generator (this happens when the load is changing drastically).

H

Hertz [Hz]

A measurement of the number of complete cycles per second of a waveform. Normal mains frequency is either 50 or 60 Hz.

HID (Human Interface Device)

The HID standard was adopted primarily to enable innovation in PC input devices and to simplify the process of installing such devices. HID class is over 20 years old and it is now implemented in all operating systems – Windows, Linux, Mac, Android, dedicated systems for NAS, kiosks etc. Although it has limited functionality comparing to the native software it is sufficient to control the connected device.

UPS with HID support will be natively detected by any operating system. It will be available for management just as the battery setup in any laptop.

There are multiple benefits coming from this solution:

  • reduced time for configuration for IT administration (i.e. if multiple units need to be setup)
  • compatibility with dedicated systems like NAS (Network Attached Storage), kiosks, ATMs
  • no security concerns for external software (i.e. in governmental or financial institutions it might be forbidden to install external software)
Hot-Swap

within a UPS system, the term ‘hot swap’ applies to any UPS module, equipment or accessorie that can be added to or removed from the UPS system with no interruption of the conditioned power directed to the critical loads.

I

IEC (International Electrotechnical Commission)

Is an international standards organization that prepares and publishes international standards for all electrical, electronic and related technologies. IEC standards cover a vast range of technologies from power generation, transmission and distribution to home appliances and office equipment, semiconductors, fibre optics, batteries, solar energy as well as many others.

IEC 62040-3 Classification

As technical development progressed, the classification VFD, VI and VFI proved to be no longer differentiated and precise enough for the UPS Market. The IEC put a stop to the proliferation of terms with the IEC 62040-3 standard and created a classification in which future UPS technologies will also find their clear place.

IEC Connectors

IEC connectors are electrical power connectors specified by IEC standards. IEC 60320 appliance couplers for household and similar general purposes is a set of standards from the IEC specifying non-locking connectors for connecting power supply cords to electrical appliances of voltage not exceeding 250 V and rated current not exceeding 16 A.

Different types of connector (distinguished by shape and size) are specified for different combinations of current, temperature and earthing requirements. The standard uses the term coupler to encompass connectors on power cords and power inlets and outlets built into appliances.

Incomer

The bus carrying the power into an electrical-substation from the nearest generating station.

Ingress Protection (IP Rating)

An IP number is often specified when referring to protection against both solids and liquids offered by enclosures around electronic equipment. The first number refers to solid objects, one being the lowest and six the highest. The second refers to liquids, eight being the highest protection.

Input Connector

Is defined as the connector type required to supply power to the UPS.

Input Voltage Range

Is defined as the range in which the UPS can work properly without transfering to Battery Mode or AVR Mode (VFD and VI respectively). With VFI UPS, it depends on the load level, before it changes to Battery Mode.

Inrush Current

The initial surge in current drawn loads, for example, to charge capacitive circuits, and it is the maximal instantaneous input current drawn by an electrical device when first turned on.

Typically, in-rush current is short enough to not influence electrical installations (it does not trip the breaker). A typical breaker allows overloads of 500% of the nominal current for some milliseconds. The UPS, as an advanced power converter, is has a lower limit and it is often not enough to acommodate the in-rush current.

Inverter

Part of the UPS system that converts DC power back to AC. Modern Inverters are sometimes called charger systems as they are also able to convert AC to DC power to charge batteries. In fact, an Inverter can be described as an Off-line UPS with external batteries and slightly longer transfer time.

Inverters are frequently used in semi-industrial environments and DIY-solutions where very long backup time for small to medium loads are required. Inverters have a very low own-power consumption and a strong charger (Inverter Charger > UPS Charger) to work with external battery banks.

Isolation

The degree to which a device like a UPS can electrically separate its input from its output.

L

LCD

A Liquid-Crystal Display is a flat-panel display that uses the light-modulating properties of liquid crystals combined with polarizers.

LCD Indicators

These indicators are displayed in the LCD of the UPS and will indicate critical information regarding the current status of the UPS itself. The indicators differ depending on the UPS model. Usual indicators can be and are not limited to: Load Level, Battery Level, operating Mode, Input Voltage, Output Voltage, and so on.

LED

A Light-Emitting Diode is a semiconductor light source that emits light when current flows through it.

LED Indicators

These indicators are usually colored LEDs, that emit a color that represent a critical status of the UPS. The indicators differ depending on the UPS model. Usual indicators can be and are not limited to: operating Mode, charging, fault alarm, and so on.

Line-Interactive (VI)

VI Products (Voltage Independent), also known as Line-Interactive UPSs, ensure uninterrupted and regulated output voltage. The build-in Automatic Voltage Regulator provides improved power output and is the main difference between Line-Interactive and Off-Line units.

Load

The electrical equipment powered by and connected to the UPS.

  • Critical Loads: Systems which directly affect the ability of an organisation to operate and which must be kept running during a mains power supply failure.

  • Non-Essential Loads: Electrical equipment that can be dropped during a mains power supply failure during load shedding.

  • Linear Loads: A load in which the relationship between voltage and current is constant, based on a relatively constant load impedance.

  • Non-Linear Loads: A load in which the relationship between voltage and current fluctuates based on alternating load impedance.

Load Shedding

Switching off non-essential equipment in order to increase the total runtime of the remaining system being powered by a finite power source.

M

Maintenance Bypass Switch

A bypass supply which is used to power the electrical equipment during maintenance, which can be either internal or external to the equipment. The UPS itself will be isolated and made safe for servicing or repair.

Make-Before-Break (MBB) Bypass

A bypass that makes contact betweeen the primary (UPS output) and secondary (bypass supply) power sources before transferring the load, to avoid any transfer-time gaps.

Mean Time Between Failure – Uptime (MTBF)

A measure of reliability and the average length of operational time between failures. This can be based on monitoring a field population, or calculated for a system based on the known MTBF values of its components to a defined process and standard. MTBF ratings are measured in hours and indicate the reliability of hardware devices such as UPS equipment.

Mean Time to Repair – Downtime (MTTR)

A measure of the average time taken to bring back a system to full operation following a failure. MTTR includes fault diagnosis time, and any time necessary to obtain replacement parts, as well as the actual repair work time.

Modular UPS

Modular UPS are Plug & Play UPS systems. They provide more flexibility and scalability than a complete cabinet containing a single pre-configured UPS. They allow the user to adjust changing capacities and let the system meet redundancy requirements of the equipment load.

Modbus Card

The Modbus Card is a communication accessory that provides a pair of RJ-45 interface for remote monitoring and controlling of the UPS. It converts standard RS232 signal to RS232 signal with specified address, which allows controlling many UPS from one computer. You can setup a desired address with jumpers (range 0-255).

Modbus TCP

Modbus is a data communications protocol. Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices.

Mode Efficiency

UPS efficiency is based on how much of the original incoming power is needed to operate the UPS. For example, an uninterruptible power supply with a 95% efficiency rating will have 95% of the original input powering the load and connected systems, with the remaining 5% energy “wasted” running the UPS.

  • Normal-Mode Efficiency: While running in Normal Mode, how much of the original incoming power is used by the UPS. The value is expressed in percentage.

  • Battery Mode Efficiency: While running in Battery Mode, how much of the original incoming power is used by the UPS. The value is expressed in percentage.

  • ECO Mode Efficiency: While running in ECO Mode, how much of the original incoming power is used by the UPS. The value is expressed in percentage.

N

N+N Redundancy

Describes the configuration and redundant capacity of a parallel redundant system. N represents the number of modules needed to meet the critical load and +N is the number of extra, redundant modules, referred to as the coefficient of redundancy. If one UPS fails the other is capable of supporting the full load.

Nominal Output Voltage

Nominal voltage is a value assigned to a circuit or system to designate its voltage class conveniently (e.g. 120/240 volts, 300 volts, 480Y/277 volts). The actual voltage at which a circuit operates can vary from the nominal voltage within a range that permits satisfactory operation of equipment.

Noise (Electrical)

Any undesirable electrical signal. A high frequency disturbance which can disrupt electrical circuits.

Noise Level [dB]

Measured in decibels. Normally measured at 1m away from the UPS.

Normal Mode

Normal Mode is only possible in Line-Interactive UPSs. The UPS takes the source as the power supply for the Load. If the source shows deviance in the voltage measurements, then the UPS will regulate the Voltage with the AVR.

O

Off-Line (VFD)

VFD Products (Voltage and Frequency Dependent), also known as Off-Line or Standy-by UPS, are the basic idea of an uninterrupted power supply system. They can mainly protect your load against power interruptions.

Off-Line Mode

In general, all current that goes from source directly to the load is called Bypass Mode. All impurities from the source are not removed. In general, Bypass Mode is used when the equipment itself is in Maintenance. It is also called Off-Line Mode, because of the VFD products. VFD product only have two possible ways of supplying power to the equipment; in Bypass Mode or in Battery Mode.

On-Line (VFI)

VFI Products (Voltage and Frequency Independent), also known as On-Line UPSs, always provide clean power. They have protection against all standard power problems in a network and they are built with a double-conversion technology which pre-converts all incoming AC, cleans it, and then supplies the Load with a new AC generated by the UPS.

On-Line Mode

On-Line Mode feeds mains electricity into a rectifier/ charger, and converts AC to DC. The DC then charges the batteries and also feeds the DC into an inverter which then converts the DC back to AC. This clean power then feeds the electrical equipment. In the event of mains overvoltage or failure the UPS continues to supply the load from its battery with no transfer delay.

Optimized Battery Management (OBM)

When the battery reaches a specific voltage threshold while being charged, it will go into floating mode (the battery is charged with a constant voltage and will charge slower). When the battery is full, the charger will go into rest mode and will not charge until the battery reaches a specific low-voltage threshold, the UPS shifts to battery mode or a self-test takes place, then the resting period will stop and the battery will start charging with a constant current again. This whole process is called optimized battery management and it will extend the battery life for up to 50%.

Opto-Isolator

Also known as optocoupler. Is an electronic component that transfers electrical signals between two electrically isolated circuits by using a short optical transmission path (by using light).

Output Connector

Is defined as the connector type available to supply power to the loads from the UPS.

Output Power Factor

Power Factor is defined as the ratio of the real power absorbed by the load to the apparent power flowing into the circuit. When VA and W are the same, we talk about power factor 1.0.

Overcharge Protection

The purpose of the overcharge protection is to avoid severe events caused by an overcharge current. It will for example interrupt the current or voltage or limits it to an acceptable value.

Overload

Overloads happen when you demand more electricity from a circuit than that particular circuit is designed to handle. That being said, circuits themselves may have different sizes or types of breakers, fuses, wires and outlets or connections. Remember wiring in a circuit is only as good as its weakest point.

Overload Capacity

The maximum level of current, voltage or power that a device can withstand before it is damaged.

Oversizing

It is recommended to use a higher power capacity UPS when the loads have an APFC function (as an example). The oversizing factor should be x2.5 of the nominal power supply that the device requires. Oversizing is just taking in consideration that maximum power consumption, peaks, in-rush currents and even harmonic distortions may occur.

Overvoltage

An abnormally higher voltage than specified in a circuit sustained for an extended period.

Own Power Consumption

Wasted energy used by the UPS to operate.

P

Parallel Operating UPS

A parallel UPS system where the total electrical requirements are met by operating a number of UPS in parallel.

Phase
  • Single-Phase: The UPS ensures the availability of your mission-critical equipment and provides clean output power to your sensitive devices. They are used in targeted protection of selected loads and are within a household budget. Designed to be user-installed, and they do not require a service contract or technician. Within Europe, single-phase consists of an AC sine-wave of 50Hz – 230V.

Decentralized Solution: The focus of this consideration is maximum flexibility and very good cost controlling by targeted protection of critical systems.

User & Maintenance Friendly: Single phase UPSs can be operated and maintained by the user itself.

  • Three-Phase: The UPS is the core of a reliable protection architecture. Usually, solutions over 10kVA supply entire installations and therefore require a three-phase connection. The UPS becomes a demanding element of the electrical installation of a building, a project, or a plant. In the end, the final solution will certainly have sufficient bridging time, will be a stable power source and will be part of the power network of a building or project. Three-phase is divided into three equal sine-waves with a phase to phase voltage of 415V.

Centralized Solution: To protect entire building complexes or parts of them.

Parallel Operation: Reduce the probabilities of a failure with a N+X Parallel Redundancy setup.

Power Conditioning

The cleaning of mains, removing sags, spikes and smoothing the suppply before redirecting to the electrical equipment.

Power Density [W/m²]

The power density of a UPS system is found by dividing its power output in Watts by the floor area it covers, in square metres. A high power density figure is an important feature for UPS systems.

Pulse Width Modulation (PWM)

A sine-wave created in an inverter by a switching action which varies with time.

Pure Sine Wave

This is the definition given to a UPS that can reproduce a sine wave with low harmonics (low distortions in the peaks). « Pure » sine wave or sine wave is important when sensitive equipment is connected to the UPS. They can improve the performance and efficiency of the connected equipment, or it will let it work properly (simulated sine wave, in the other hand, can cause irregular operation of sensitive devices).

R

Rack

see Form Factor

Rack-Mount-Kit (19″)

It is a set of rails installed in a 19 inch rack cabinet. These rails carry the weight of the UPS inside the cabinet. In every case, the rack-mount-kit is an additional accessory (not included in the UPS content-package).

Additionally you will use « rack ears » to fix the UPS inside the rack cabinet to prevent it from sliding back and forth, this item is included in the content-package of the UPS.

Rack Units [U]

Rack Units [U] is the measuring unit for the all RACK-UPSs. 1U = 44 cm height. This way the User can plan his Rack-System in an ideal way.

Raw Current

Mains which has not been cleaned or converted.

Reactive Power

Wasted energy (var) returned back to the incoming AC power supply. The portion of instantaneous power that results in no net transfer of energy but instead oscillates between the source and load in each cycle due to stored energy. Reactive power exists in an AC circuit when the current and voltage are not in phase.

Real Power

A measure of the actual power drawn by the electrical equipment. Also know as active power.

Recharge Time

Normally the recharge time is in hours and the percentage achieved should be 90% of the battery level (after 90%, batteries usually go into floating mode, and charge with decreasing current).

Rectifier

Component of the UPS that converts an AC supply into a DC supply (this process is called rectification). Many applications of rectifiers, such as power supplies for radio, television and computer equipment, require a steady constant DC voltage (as would be produced by a battery).

Rest Mode

Part of the Optimized Battery Management (OBM). A battery charging state used on UPS batteries, designed to maximise battery life. In this state their is no current flowing into the battery. Only if the internal battery voltage level reaches a specific lower level the charger will start charging again with a constant current, and the resting period will stop.

RMS (Root Mean Square)

This is the mean value calculated as the square root of the quotient of the sum of the squares of the observed numbers and their number. For alternating electric current, RMS is equal to the value of the constant direct current that would produce the same power dissipation in a resistive load.

RoHS (Restriction of Hazardous Substances)

This directive restricts (with exceptions) the use of ten hazardous materials in the manufacture of various types of electronic and electrical equipment.

RS-232

A serial communications protocol. It may be used between a UPS and a computer to communicate alarm, status or control signals and instructions.

S

Sag

It is a reduction of AC voltage at a given frequency. Sags are usually caused by system faults, and are also often the result of switching on loads with heavy startup currents – also called dip.

Sine Wave

The power supplied through the incoming AC line is a sine wave and is the optimal waveform for electrical equipment.

Single-Phase

see Phase.

SNMP (Simple Network Management Protocol)

Communication protocol that allows hardware with a TCP/IP connection within a network to be monitored and controlled.

SKU

Stock Keeping Unit, similar to article number.

Solar Inverter

A solar inverter will function as a centralized power solution to combine and coordinate: (1) the incoming power from the grid, (2) the energy production of the solar panels, and (3) the stored energy in the battery system. There are 2 main types:

  • Off-Grid: off-grid solar inverters are multi-functional inverters, with a solar charger, ups functions, and battery management connectivity to offer an uninterruptable power supply. They are mainly used in « island » solutions, where the produced solar energy will not (cannot) be fed back into the power grid.
  • On-Grid: just like the above mentioned. Additionally they can feed the solar energy back to the power grid. Depending on the country of residence. Many countries support this and will reimburse part of the energy costs.
Spike

Large voltage disturbances superimposed onto the normal ac supply with a short duration. These spikes are usually the result of nearby lightning strikes, but there can be other causes as well. The effects on vulnerable electronic systems can include loss of data and burned circuit boards. Also see, transients.

Standby Mode

The UPS has a Mode in which the device is not operating and not delivering energy to the loads. In Standby Mode the UPS will still have its own power consumption, just like a TV, that has the LED on, but not delivering any image on the screen. After turning the UPS on, the UPS will go in standard operation mode.

Stepped Sine Wave or Simulated Sine Wave

Also known as modulated sine wave. Both waveforms, stepped sine wave and pure sine wave are produced by an inverter. The most important difference is that the stepped sine wave has a significant slower pulse rate and therefore the adjustment to the electronics and load will be not be optimal.

Surge

Increases in voltage above the mains power supply nominal, which generally lasts for several cycles. The most common cause is heavy electrical equipment being turned off. Under this condition, computer systems unprotected by a UPS may experience memory loss, data errors, flickering lights and equipment shutoff.

Surge Protection

Surge protection shields electronic devices and appliances from surges in the electrical power or from transient voltages that flow from the power supply.

UPS can successfully protect against many network problems, like for example: overvoltages or power outages. Unfortunately, surge protection is not a main design feature of the UPS, but only a secondary function. The UPS is only able to reduce the impact of a surge caused by a lightning. In case of a lightning applying full energy to the UPS, there is no chance it will protect your equipment.

Furthermore, surge protection bases on absorption of the energy by a varistor. The varistor is worn out and wont work after absorbing big number of small surges or small number of big surges.

T

Topology
  • Off-Line (VFD): VFD Products (Voltage and Frequency Dependent), also known as Off-Line or Standy-by UPS, are the basic idea of an uninterrupted power supply system. They can mainly protect your load against power interruptions.

  • Line-Interactive (VI): VI Products (Voltage Independent), also known as Line-Interactive UPSs, ensure uninterrupted and regulated output voltage. The build-in Automatic Voltage Regulator provides improved power output and is the main difference between Line-Interactive and Off-Line units.

  • On-Line (VFI): VFI Products (Voltage and Frequency Independent), also known as On-Line UPSs, always provide clean power. They have protection against all standard power problems in a network and they are built with a double-conversion technology which pre-converts all incoming AC, cleans it, and then supplies the Load with a new AC generated by the UPS.

Total Harmonic Distortion

A measure of all the harmonics induced in a system compared to a normal sinewave. Lower THD implies lower peak currents, less heating, lower electromagnetic emissions, and less core loss in motors.

  • THDi: Stands for the total harmonic current distortion of the input waveform. It is generally accepted that the THDi should be kept low to avoid excessive current distortion at the point of common coupling within a building due to the cumulative effect of all connected equipment.

  • THDv: Voltage total harmonic distortion.

Three-Phase

see Phase

Tower

see Form Factor

Transfer Time

The time it takes the UPS to transfer a load between supply sources (e.g. between Normal Mode, Bypass Mode and Battery Mode). Also known as switching time. It can also refer to the time it takes for the UPS to switch the power back to the mains once the issue has been resolved. It can fall anywhere between zero and 20 milliseconds.

Transients

High energy burst voltage disturbances, with a short duration, superimposed onto the normal supply. The impulsive transient is what most people are referring to when they say they have experienced a surge or a spike.

U

Undervoltage

An abnormally lower voltage than specified in a circuit sustained for an extended period.

UPS (Uninterruptible Power Supply)

It is best defined as a backup power supply that, in case of a power failure, allows enough time for an orderly shutdown of electronic equipment. It is capable of maintaining power to a load for a defined time irrespective of the state of the mains power itself.

V

VFD (Voltage and Frequency Dependent)

see Off-Line (VFD)

VI (Voltage Independent)

see Line-Interactive (VI)

VFI (Voltage and Frequency Independent)

see On-Line (VFI)

VRLA Battery (Valve Regulated Lead-Acid)

These batteries emit virtually no gas, require no topping up and need no special ventilation and are commonly used within the UPS.

There are two primary types of VRLA batteries, absorbent glass mat (AGM) and gel cell (gel battery). Both types of VRLA batteries offer advantages and disadvantages compared to flooded vented lead–acid (VLA) batteries.

Volt [V]

A measure of electrical force or pressure, which can be expressed as VAC or VDC.

Volt-Free Contact

It refers to a secondary set of contacts of a relay circuit which does not make or break the primary current being controlled by the relay. Usually, with a Dry-Out Contact, you can get a signal out off the UPS and automate external devices. With a Dry-In Contact, you can remotely turn the UPS on and off. Also known as dry contacts.

W

Watts [W]

A measure of the real power drawn by a load.

WEEE (Waste Electrical and Electronic Equipment)

Also described as electronic waste or e-waste. Informal processing of electronic waste can lead to adverse human health effects and environmental pollution.

WEEE Directive

The WEEE Directive, or European Community Directive 2012/19/EU, set collection, recycling and recovery targets for all types of electrical goods to prevent further adverse human health effects and environmental pollution.