The soft starter is suitable for coal mines containing explosive gas (methane) and coal dust.In an AC 50Hz, voltage 1140V or 660V, neutral ungrounded power supply system, various forms of soft start (such as current clipping, voltage ramp and power torque ramp) are performed on three-phase squirrel-cage motors with currents up to 200A and 400A.The controller also has the perfect protection function and the fault display function, greatly reduces the time of troubleshooting.