Efficiency is a key performance indicator of motors, especially in the current energy-saving and low-carbon environment, where users attach great importance to the compliance of motor efficiency indicators.

From the concept of motor efficiency, it can be understood that the output power is less than the input power, which means that the conversion and transmission process of motor power is a process of attenuation.

But according to the law of conservation of energy, the energy that is “thrown away” is only converted or consumed in different forms. Starting from the working principle of the motor, we divide the process of motor input and output into several segments, and briefly analyze and understand the process of energy attenuation.

The first process: The electrical power input to the stator (P1) will generate copper loss (Pcu1) and iron loss (PFe) due to the current in the stator. Theoretically, the iron loss of the motor is composed of stator iron loss and rotor iron loss, but due to the particularly small rotor frequency, the rotor iron loss can be omitted, that is, the iron loss of the motor is mainly generated by the stator part. From the analysis of the process of energy conversion and transmission, the electromagnetic power (Pme) that can be transmitted to the rotor is less than its input power P1.

The second process: The electromagnetic power (Pme) received by the rotor from the stator is reduced again to the total mechanical power (Pmec) that can be converted due to the copper loss (pcu2) present in the rotor.

The third process: The rotor part is converted to the total mechanical power (Pmec). Due to the mechanical loss (pmec) caused by the movement of the rotor, as well as the additional torque loss (pad) caused by tooth harmonics, the output power (P2) of the motor is attenuated again on the basis of the total mechanical power (Pmec) of the rotor.