UNINTERRUPTIABLE POWER SUPPLY(UPS) Working principle
WHY DO WE NEED UPS It provides protection against power outages(failures). In medical equipments such as E C G, Pace maker, in operation theatre which saves human life. Increase the reliability of the machine. It can save the required work and saves time.
Points to Remember The electricity used in home applicants is AC current. The storage form of current is DC. An alternating current is represented as sin waves An direct current is represented as +ve half cycle
Rectifiers: Its nothing but the diodes . It is a device that converts AC to DC current . The rectifiers are divided into two: Half-Wave Rectifiers. Here AC current is been allow to pass through half of the AC cycle and blocked in other half cycle. Such circuits are known as half-wave rectifiers
Full-Wave Rectifiers. Here AC current is been allowed to pass during the +ve half cycle diode d1 conducts. During the –ve half cycle diode d2 conducts and form complete DC current , they are known as full-wave rectifiers.
Battery: UPS battery is used as a storage energy device, Its main function is: When the electricity is normal, the energy is converted into chemical energy and stored in the battery. when the electricity fails, the chemical energy is changed back into electrical energy provided to the inverter or the load. Inverters: A power supply which produces an AC output, usually from a DC input. Filters: A filter is a frequency selective circuit or device that is designed to pass frequencies within a specific range, while rejecting all other frequencies that fall out of its range. Spikes: Its a sort of sudden voltage that would damage your equipment. Spike Buster: is used to protect electronic devices from spikes in the AC voltage.
Working principle of UPS Basically a UPS works in two conditions 1) Off line UPS 2) On line UPS Off line UPS: when there is normal presence of power the current passes through spike busters and filters which removes the abnormal changes of voltage and passes through the load. Thus acts as a stabilizer. On line UPS :In the absence of power the stored DC current in the battery gets discharged and passed to the inverters, where DC current is been converted to AC. And given to the load. In this condition current is free from all power problems like fluctuations, spikes, frequency drifts etc.
Demerits of UPS AC-DC-AC conversion process in 25% to 30% power loss. The heat generated due to power lose reduces the life of the battery. Because of the technology used, online UPS is more expensive.