Uninterrupted Power Supply (UPS)
The device that maintains continuous power supply even on the absence of mains power supply is called UPS or Uninterrupted power supply. This is usually connected between the main source and the working system. It switches from the mains power supply to the battery power instantaneously whenever there is a fault in the mains power supply or the power supply is not there at all. It is generally used to protect typically computers, telecommunications equipment, and other electrical equipment where there is a chance of power failure. UPS are available from 200VA onwards to large systems which can support the power supply of multistoried buildings. It is typically the need of all data centers, and computer network systems. Sometimes in large systems it is used in conjunction with generators but it is not to be confused with standby generators. UPS are used for short and instantaneous power supply needs though for longer terms it may be used with a generator.
Some common problems for which UPS are required are
- power failure
- voltage sag
- voltage spike
- under voltage or brown out
- over voltage
- line noise
- harmonic distortion
There are different types of UPS in the market they are on-line and off-line. The off-line variety is also sometimes known as standby UPS. The on-line UPS is continuously provides power supply from its internal source and drains the battery and the battery gets charged continuously. On the other hand the off-line or stand by system connects the power supply to the load only through its stabilizer circuit and switches to the battery only when there is a problem with the power supply.
Other online UPS systems are
- line interactive
- online single conversion system
- delta conversion online
- dual conversion online
- Ferro-resonant
- DC systems
- outdoor UPS
- fuel cell UPS
Now when you go for buying a UPS what are the features we see:
- First is the determining of a required volt ampere or power rating of the system. This is the maximum power load UPS can handle and typically it should not exceed 80% of the connected load. For connecting some of the motorized loads more power rating is required as motors while taking initial torque require more power.
- The second is the amount of backup time given by the UPS. The more the backup time is given the better is the UPS.
- The usage of the UPS is also to be taken in consideration. If the system is to be shut down by the UPS a proper UPS with software and communication port for the computer is to be chosen. But if the UPS is to be only used momentary before the generator starts then consideration should be taken so that the generator output matches with the input of the UPS.
- Care should be taken that the UPS does not make harmonic distortions or it is to be within specified limits which does not affect other systems.