The system efficiency is equal to the product of frequency converter efficiency and motor efficiency, and the system efficiency is higher only when both work at higher efficiency. From the perspective of efficiency, the following points should be noted when selecting converter power.

1) It is most appropriate when the power value of the converter is equivalent to the power value of the motor, so as to facilitate the converter to operate under the high efficiency value.

2) At the same time that the power grading of the converter is different from that of the motor, and the power of the converter should be as close as possible to that of the motor but slightly larger than that of the motor.

3) When the motor is in frequent starting, braking or starting with heavy load and working frequently, a large-scale frequency converter can be selected to make use of the frequency converter for long-term and safe operation.

4) According to the test, the actual power of the motor have a surplus. You can consider using a frequency converter whose power is less than the motor power, but you should pay attention to whether the instantaneous peak current will cause the over-current protection action.

5) When frequency converter and motor power are not the same, the setting of energy saving program must be adjusted according to achieving higher energy saving effect.