The refiner control system using D71 inverter has been put into operation for more than three years, and has achieved good economic and social benefits:

• The control device operates reliably, has good environmental adaptability, can resist harsh environments such as oil pollution, dust and damp heat, and has a low failure rate;

• Excellent current limiting characteristics, strong overload capacity, can effectively reduce frequency conversion overload, overcurrent protection, and maximize production continuity;

• The feeding amount is controlled by the actual running current of the motor, and it has overload pre-alarm function and trip-free function, which can ensure the safety of the motor and the continuity of production;

• The economic benefits are remarkable, the power saving effect is more than 20%, and the entire investment increased by the frequency conversion control system can be recovered in more than one year.