New GTO uninterruptible power supplies with self-diagnosis functions

There is an increasing demand on the uninterruptible power supply (UPS) equipment for reduced energy consumption and installation space and improved reliability. This paper describes the system construction of the microprocessor-based UPS system using turn-off thyristors (GTO). The constant voltage control is performed by a GTO step-up chopper, and the GTO inverter normally is run at a fixed pulsewidth of 120°. During the overcurrent limitation operation, the PWM control on the GTO inverter is done in software. New functions are incorporated into the control circuit, such as operation procedure guidance, fault recording and fault diagnostic functions, to realize easy operation and shorten MTTR.