A bypass transfer method for UPS system

This paper proposes a bypass transfer method without parallel feeding between utility power line and uninterruptible power supply (UPS). This system has ACSWs consists of a bi-directional thyristor and a magnetic contactor both utility power line and UPS line. The control board observes the condition of utility power and UPS to operate ACSWs. A proposed method has instantaneous interruptible period purposely. Therefore, it can be transferred to each line instantaneously without additional reactor or complex control system. Its effectiveness is verified through Experiment in a 4kW prototype. It can be transferred each other only 500μsec interruption without parallel feeding periods.