Thyristor circuit breaker devices for energy recovery applications

An auxiliary switched thyristor circuit breaker (TCB) with a switching free-wheel diode was developed to overcome some special problems when protecting an AC line commutated thyristor inverter fed from a large `lumped´ inductive DC supply. The particular application to which an 1800 A/750 V TCB has been applied, was to provide fast acting overcurrent protection on the DC side of a regenerative test circuit for continuous load testing of diesel-electric shunting locomotive engines, rated up to 600 kW. The inverter was used to recover 70-80% of the energy normally dissipated during the tests. The power delivered in the inverter mode typically being 200-500 kW, could be used locally to reduce the peak power demand on the local AC system. The energy saving was estimated to be 450000 kWh/year