Power electronics reliability in rail traction

Power electronics, as applied to the traction package, has thus grown from (usually a pair of) straightforward bridge rectifiers with no controls, through thyristor bridges and choppers controlled with analogue electronics, to microprocessor controlled, GTO based variable voltage-variable frequency inverters fed from (microprocessor controlled, GTO based) 4-quadrant power converters and incorporating a (microprocessor controlled, GTO based) rheostatic braking chopper. This represents a significant increase in the number of power semiconductors used in traction control, along with a huge increase in the complexity of the controlling circuitry, admittedly against a desire for improved performance both in terms of function and cost of ownership. In considering the rate of failures and their effects on service, this substantial increase in the number of devices and associated control electronics should be taken into account