Motor soft starter and protection method executed by same

The invention provides a motor soft starter and a protection method executed by the motor soft starter. The motor soft starter is connected between a three-phase power supply and a motor load. The circuit comprises first, second and third phase bridge arm circuits and a control unit. Each phase bridge arm circuit comprises a first power semiconductor switch, a second power semiconductor switch and a driving protection unit. The driving protection unit collects first voltage between the first end and the second end of the first power semiconductor switch and second voltage between the first end and the second end of the second power semiconductor switch, judges whether the first voltage and the second voltage are larger than threshold voltage or not, and responds to the situation that the first voltage and/or the second voltage are/is larger than the threshold voltage. And a control unit which controls to turn off the first and second power semiconductor switches and outputs a turn-off signal to the control un