Frequently used UPS terminology and corresponding definitions.

AC – ALTERNATING CURRENT POWER

AC is the type of power that comes from the grid supply. It is the most widely used type of supply to feed almost every type of load. The output of a UPS is AC power either 220 volts 1 phase or 400 volts 3 phase.

DC – DIRECT CURRENT POWER

DC is the type of power that comes from a battery or rectifier. It is the most widely used type of supply to feed a backup UPS system inverter.

RECTIFIER

A UPS rectifier changes the AC mains power into battery power (DC) which is used to charge the inline battery and feed the UPS inverter.

INVERTER

A UPS inverter changes the DC power from the battery and rectifier into AC mains power.

STATIC BYPASS SWITCH (SBS)

The static bypass switch is the third major component of a UPS backup system. It allows the load to either be fed from the UPS inverter (normal operation) or in an overload situation it will transfer the load power supply from inverter to mains until the overload ends. It is a very high-speed electronic switch that does these transfers without a break in power supply to the critical UPS load.

MANUAL BYPASS SWITCH

The manual bypass switch allows the UPS user to manually close a switch, which will connect the UPS input mains supply to the load. It is generally used only during maintenance and when the UPS has a fault and is off.

RUN TIME

A UPS run time is the backup battery time you will get from the UPS battery when the power goes off. Generally, a UPS run time is 5 to 20 minutes depending on the connected battery. The run time is load-dependent and the smaller the load on the same size UPS the longer the run time.

BLACKOUT

A blackout is the term used when the power supply from the power grid goes off completely or when its voltage gets so low that no equipment will switch on. A UPS in between the load and the mains power supply will prevent the load from being affected.

BROWNOUT/DIP/SAG

A brownout also called a power dip or sag, is the term used when the power supply from the power grid goes off for very short periods, un-planned. These often occur when the supply grid is heavily loaded, such as in peak periods when demand exceeds supply, and the voltage starts to drop. It usually causes loads that are running to reset and can cause data loss in a computer or even complete failure. A UPS in between the load and the mains power supply will prevent the load from being affected.

SURGES/SPIKES

A power surge or spike is when the supply grid voltage goes extremely high due to lightning, switching of big supply grid circuit protection, or even when manufacturing and mining loads like ARC furnaces turn on and off. A UPS in between the load and the mains power supply will prevent the load from being affected.

MOVs

An MOV is a Metal Oxide Varistor, which is a device that is used to prevent spikes and power surges from damaging the load. It is the basic starting point for surge and lightning protection. No matter how good your surge/lightning protection is, there are no guarantees that lightning will not damage the load. A common myth is that a UPS protects the load from lightning. A UPS is not a lightning suppression device. Lightning will often go through the UPS and still damage the load.

AUTOMATIC VOLTAGE REGULATOR or AVR, ALSO CALLED CVT

A voltage regulator regulates the voltage to the connected output if it should vary by up to 20%. It is also known as a CVT or constant voltage transformer. It can NOT be used as a backup power source instead of a UPS, as it does not create any power; it simply adjusts the voltage by means of regulation.

POWER FACTOR

Power is measured in VA (Volt amperes – Active power) or W (Watts – True power). The VA value will either be equal to or bigger than watts but never less in value. The power factor determines the watt rating of a UPS. If a UPS is say 1000 VA with a rating of 0,8 power factor (PF), then it can only deliver 800 watts true power. If it is rated at 0,6 PF, then it can only deliver 600 watts power. So the same VA UPS system is not necessarily the same power rating. The cost per Watt is, therefore, what you need to compare. The cheapest is not necessarily the most cost-effective when the cost per Watt is considered.

OFFLINE UPS

An off line UPS uses the mains supply for the load. When the power fails it switches on its inverter and powers the UPS load from the backup battery. Because the inverter is normally of there is a switch on time with a break in power to the load. It will work of for a PC but not all types of loads.

LINE INTERACTIVE UPS

A line interactive UPS uses the mains supply for the load. It is similar to an offline UPS but does have limited power filtering of the mains and it has a quicker switch on time.

ONLINE UPS

An on line UPS more commonly called an online double conversion UPS is on all the time and ensures the inverter load gets clean filtered pure AC power.

RECYCLABLE BATTERY

A recyclable battery in Africa, is considered a battery from a UPS that is 100% green and every component is reused to make a new battery. This would mean the battery must be a lead acid.

VRLA BATTERIES

A VRLA battery stands for Valve Regulated Lead Acid battery and is designed for use in UPS systems

SINEWAVE INVERTER

A Sinewave is the purest form of power that can be derived form an inverter.

GENERATOR

A generator is an electro-mechanical device using an Engine and fuel source to drive and Alternator which then generates power.