Auxiliary inverters for traction

Auxiliary power supplies are required for operating air conditioning units, ventilation fans, lighting and battery charging. Traditionally this function has been fulfilled by motor-alternator sets. In recent years, however, GTO development, availability and price have made 3 phase GTO auxiliary inverters an attractive alternative to MA sets. GEC Traction have recently supplied a prototype 3 phase static auxiliary inverter to Hong Kong MTRC, which has been in passenger service since May 1987. Successful trials led to an order for 41, 65kVA naturally cooled static auxiliary inverters. The first of these has been in passenger service since February 1988. The authors discuss the advantages of static auxiliary supplies and examine the design features of naturally ventilated GTO auxiliary inverters. System control and performance is also described