The DYQ3 series is used a special liquid resistor to be connected in series to the rotor circuit of large and medium slip ring motor, the liquid resistor get to work when the motor starting and it can automatic, stepless and continuous removal during the preset time, then the motor can start smoothly under ideal starting current condition. Eventually the motor can accelerate balanced. This plays an important role in protection of motor, electric equipment，power system and saving electricity. As well as the well-designed of system starting, stop, error protection, liaison and display, making the liquid resistor starter have high degree of automation, small starting current (less than 1.3 times for rated current in general), can start successfully when power system have low voltage, and reducing the capacity of transformer remarkably. So DYQ3 series liquid resistor starter is the most ideal starting equipment for heavy load device such as: ball crusher, hoister, compressor, blower and water pump etc.