UPS (UNINTERRUPTED POWER SUPPLY)
UPS means Uninterrupted Power Supply. It is used for electronic instruments where continuous (or uninterrupted) power supply is required. It consists of one rectifier, battery &an inverter. Inverters are of various types – On Line, Off Line etc.
Rectifier– The function of Rectifier is to convert AC into DC & provides battery charging voltage. Its output is connected with battery.
Battery – The function of battery is to store DC energy in it. Its output is connected with the inverter through a static switch which operates when power goes off.
Inverter – It converts DC into AC when AC power goes off. It is connected with load.
Working principle – When normal AC supply is available, load is connected with normal AC supply. AC supply is also connected with rectifier & rectifier converts AC into DC & provides charging voltage for battery. And battery gets charged & DC energy is stored in it. When power goes off, battery is connected with inverter through a static switch (which is off when normal AC power is available) & DC is converted into AC & immediately load gets alternate AC supply. When normal AC supply resumes, the static switch gets open & battery is disconnected with inverter & load is again connected with normal AC supply. Also discharged battery is charged again through rectifier.
There are two types of UPSs – 1) Off Line UPS 2) On Line UPS
OFF LINE UPS – When normal AC supply is available, load is connected with AC mains & batteries are charged (throgh battery charger) from AC mains to maintain a rated volage. But when power fails, battery is connected with inverter & inverter converts DC inro AC & which is fed to load. When AC supply is restored, battery is disconnected from inverter & load is again connected with normal AC supply. And this procedure is repeated.
ON LINE UPS – In this case, load is always fed from AC which is coming from inverter. Normal AC suppply is connected with charger, charger charges the battery & battery is directly connected with inverter & inverter converts DC into AC. And load is connected with inverter.