Abstract: According to the topology of conventional chopper cascade speed system, the transient process of main loop during of contactor operation was analyzed when device failed. Because the contactor action required a longer time, equipment was vulnerable to the impact of high voltage, high current during the contactor action, which caused damage to power electronic devices. For contactors' drawbacks, the main circuit topology with electronic protection circuit was designed. Then transient process of conventional chopper cascade speed system and chopper cascade speed system with electronic protection circuit under high voltage power failure conditions was analyzed, and theoretics was detailedly deduced. The basis of theoretical analysis under high-voltage power failure condition was obtained. Simulation model of conventional chopper cascade speed system and with electronic protection circuit was built respectively in Matlab. Simulation results show that electronic protection circuits effectively solve the problem of high-voltage power failure under active inverter structure and inverter subversion.

Key words: electronic-protection circuit, high-voltage power failure, active inverter, inverter subversion