At the start of the compressor, the current of the motor will be 5-6 times higher than the rated current, which will not only affect the service life of the motor but also consume more power. The system will have a certain margin on the motor selection at the time of design. The speed of the motor is fixed, but in the actual use process, sometimes it is necessary to run at a lower or higher speed, so it is very necessary to carry out frequency conversion. The frequency converter can realize the soft start of the motor, achieve the purpose of energy-saving speed adjustment by changing the input voltage frequency of the equipment, and provide the equipment with Overflow, overpressure, overload and other protection functions. The domestic frequency converter is better made by manufacturers such as Sanjing and Yingweiteng.