Energy saving of frequency converter is mainly reflected in the application of fans and water pumps. After variable frequency speed regulation is adopted for fan and pump loads, the power saving rate is 20% - 60%, because the actual power consumption of fan and pump loads is basically proportional to the third power of speed. When the average flow required by users is small, fans and pumps adopt variable frequency speed regulation to reduce their speed, and the energy-saving effect is very obvious. The traditional fans and pumps use baffles and valves for flow regulation, the motor speed is basically unchanged, and the power consumption changes little. According to statistics, the power consumption of fan and pump motors accounts for 31% of the national power consumption and 50% of the industrial power consumption. It is of great significance to use variable frequency speed regulation devices on such loads. At present, the more successful applications are constant pressure water supply, various fans, central air conditioning and variable frequency speed regulation of hydraulic pumps.