| Abstract |
Self-turn-off devices offer great benefits for traction inverters as they can commutate high currents independently of the amplitude of the input voltage: this enlarges the field of economic operation of the inverter. Thus GTO thyristors supersede forced-commutation in traction main drives, transistors in auxiliary drives. The expense for an GTO high-power inverter is considerably determined by the snubber circuits relieving the GTOs from switching stress and the protection against the consequences of short-circuits. The low-loss asymmetric "Undeland" snubber circuit gives the best overall performance. Immersed fluid cooling systems show great advantages for high power GTO inverters. The fluorocarbone (R113) evaporation cooling is highly effective, especially when combined with a water intermediate system. This inverter design for a 1400 kVA traction inverter is applied first on the four diesel-electric locomotives DE 1003 for Ruhrkohle AG. The auxiliary drives are equipped with three-phase motors, supplied by 4 individual transistor inverters fed from the main d.c. link via a GTO half-bridge inverter. The power applied is controlled according to the actual demand and moreover, during dynamic braking the brake energy is utilized. |
