The grinder and grinding wheel motor used in the standard machining are all operated according to the traditional starting circuit. After the motor is started, it operates according to the rated speed. Due to the fluctuation of the grid voltage and the constant change of the friction load of the grinding wheel workpiece, the speed error of the motor will be affected. Generally, the starting circuit of the standard grinding wheel motor has only one processing speed, which is difficult to adapt to different workpiece sizes and require different processing relative linear speeds, so that the processing precision of the processed workpiece is difficult to guarantee. Therefore, in order to improve the efficiency of machining quality and save energy, the application of frequency control technology to grinder can achieve satisfactory results. There are many kinds of products processed in the machining industry, the size and size of workpieces are different, and the machining accuracy is different. It is difficult to adjust the spindle speed to meet the workpiece processing line speed. Because of the stress bending process during the machining process of the shaft, grinding wheel will produce different feed torque, which will bring different changes in the wheel speed and torque, and produce vibration knife / burn pattern. The grinding accuracy is awesome, resulting in low productivity and low quality. With the development of power electronic technology, the technology of frequency conversion and speed regulation is more and more popular. Among them, stepless speed regulation by frequency converter, soft start and constant torque output greatly meet the requirements of machining equipment for constant speed / constant torque