An uninterruptible power supply (UPS) is a device connecting the power source and computer. It ensures that the electrical flow is uninterrupted. After a power failure, an uninterruptible power supply makes use of batteries to keep the computer running for some time. It is recommended as compared to standby generators, which offer no protection from momentary power interruption. The standby generators may also bring about momentary power interruption when switched on whether automatically or manually. The uninterruptible power supply devices provide protection from brownouts, power surges, and line noises.
The uninterruptible power supply has three components. The rectifier stores line power in the battery once AC power is converted into DC power. The rectifier charges the battery so in case of power disruptions only the battery is affected and not the system. The battery stores power for use after power interruptions. Determining the length of time the uninterruptible power supply will continue supporting the computer. The inverter is used for the conversion of the battery’s DC power into AC power for the computer to utilize.
Uninterruptible power supply systems are threefold- off-line, online, and line-interactive. The offline UPS makes the AC line the primary power source. Any change in voltage or current detected by UPS will make it switch to the backup battery automatically. Restoring the AC power switches back to the UPS. Four milliseconds is the acceptable switchover time that normal computer power units can tolerate. A longer power failure will make the equipment shut down. The offline UPS is cheap and manufactured especially for home users.
Line-interactive UPS has a separate battery charger. Inverter switches off an offline UPS when charging the battery to convert its DC power into AC power from the output to protected devices. While an AC power line is the primary power source a battery is secondary. The inverter charges the battery when the line power is in operation. A power interruption triggers the transfer switch to open and operate in reverse. Compared with the UPS topology line-interactive UPS provides additional filtering for the inverter is always on and attached to the output. Being more expensive than offline UPS the line-interactive UPS is costlier and used as a backup for corporate workstations. The delta conversion UPS is modified from the line-interactive UPS. It is a configuration where the primary power source gets blended with the power from the inverter and converter.