With the progress and development of industry in modern times, there is a need for energy conservation and emission reduction. Nowadays, frequency conversion technology is increasingly widely used in various mechanical equipment. As a leader in the refrigeration industry, Davos is the first to introduce variable frequency chillers. In line with the current trend of technological development. Make our contribution to energy conservation and emission reduction in society. The energy-saving of frequency converters is mainly reflected in the application of fans and water pumps. In order to ensure the reliability of production, various production machinery has a certain margin when designing and using power drives. When the motor cannot be at full load