Using IGBT in Quench Protection of a 2 MJ SMES Magnet

In order to increase energy dumping speed, IGBT (insulated gate bipolar transistor) is used in quench protection of a 2 MJ superconducting magnet. 88 resistors, each connects in series with an IGBT, are connected in series-parallel connection to form a controllable varistor. On/off of the IGBTs are controlled by two single chip processors. Energy dumping with nearly constant magnet terminal voltage is realized in training quenches of the magnet. The necessary breaking capacity of the circuit breaker is also lowered. Details of quench protection electric circuit design and experimental results are presented.