According to the topology of conventional chopper cascade speed system, this paper analyzes the transient process of main loop of contactor protection when device failure. Because the contactor action requires a longer time, equipment is vulnerable to the impact of high voltage, high current during the contactor action, and cause damage to power electronic devices. For contactors and fast-cut protection drawbacks, the main circuit topology with electronic protection circuit is 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 are analyzed, and theoretics is detailedly deduced. The basis of theoretical analysis under high-voltage power failure condition is got. Finally, the conventional chopper cascade speed control system and with electronic protection circuits for high-voltage power failure conditions are tested on the simulated load test platforms. Experimental results show that the theoretical calculation is consistent with the actual measured values, and verify that electronic protection circuits effectively solve the problem of high-voltage power failure and inverter subversion under active inverter structure.