Is there a concept of energy-saving grades for variable-frequency motors?

The classification of energy efficiency grades for ordinary large and medium-sized high-voltage asynchronous motors can be based on GB 30254-2013, which specifies the energy efficiency limits and grades for high-voltage three-phase squirrel-cage asynchronous motors. As for the efficiency testing of variable-frequency motors, it is highly dependent on different frequency converters and tuning methods; therefore, there are currently no relevant standards, meaning that variable-frequency motors do not have defined energy efficiency grades. Difference between high-efficiency energy-saving motors and variable-frequency energy-saving motors: High-efficiency energy-saving motors improve the operating efficiency of the motor itself through manufacturing processes. Variable-frequency energy saving refers to conserving electricity by adjusting the motor speed; however, the energy conversion efficiency does not increase but rather decreases due to the losses incurred by the inverter. Variable frequency speed control is mainly used in situations where the load varies, and it offers a significant energy-saving effect. In simple terms, its energy-saving principle involves changing the frequency as needed, thereby altering the output power. In situations where the load is stable, that is, in cases where speed control is not required, using an inverter reduces overall efficiency and results in unnecessary power consumption. In situations with large load variations, both methods can help save energy, but variable frequency speed control enables a much greater reduction in energy consumption. Compared to ordinary motors of the same power, high-efficiency energy-saving motors can only achieve a few percentage points more energy savings. Motors powered by inverters are called variable-frequency motors, and they differ from ordinary motors. Driving an ordinary motor directly with an inverter can cause damage to the motor.