The liquid rheostat is used to adjust the rotor current of the slip ring motor. It can adjust the current of the motor immediately in the crushing process and the impact current, so that the current is maintained at the rated current value. Siemens 1200 PLC controller, Ethernet network and high voltage switchgear for communication; AB/SIEMENS servo driver is used to adjust the electrode position, and the response to overload regulation is fast. At the same time installed integral temperature, conductivity measuring device, on-line monitoring and through the LED screen in the electrical cabinet door display parameters.