The efficiency of motor is mainly determined when designing and selecting. For example, the efficiency of permanent magnet synchronous motor (PMSM) is higher than that of AC asynchronous motor, and you need to work efficiently. You need to choose servo control system instead of variable frequency speed regulation system. Of course, the cost is more expensive, so efficiency is closely related to cost.

To improve the efficiency of the motor, the essence is to reduce the loss of the motor. The loss of the motor can be divided into mechanical loss and electromagnetic loss. For AC asynchronous motor, the current will produce copper loss and conductor loss through the stator and rotor windings, while the magnetic field in the iron will cause vortex current, resulting in lag loss, the high order harmonics of the breath magnetic field will produce stray loss on the load, and there will be wear loss in the process of bearing and fan rotation.

In order to reduce the loss of rotor, the resistance of rotor winding can be reduced, the wire rod with relatively thick and low resistance can be used, or the slot cross section area of rotor can be increased. Of course, the material is very critical. The loss of copper rotor will be reduced by about 15%. At present, the induction motor is basically aluminum rotor, so the efficiency is not so high.

The same copper loss on the stator can increase the slot face of the stator, increase the full slot rate of the stator slot, and shorten the end length of the stator windings. If the permanent magnet is used to replace the stator windings, there is no need to pass through the current, of course, the efficiency can be improved obviously, which is also the fundamental reason why the synchronous motor is more efficient than the asynchronous motor.

The iron loss of the motor can use the silicon steel sheet of good quality, reduce the loss on the magnetic lag, or prolong the length of the iron core, which can reduce the flux density and increase the insulation coating, and the heat treatment process is also very important.

The ventilation performance of the motor is more important, the temperature is high, the loss will of course be very large, and the corresponding cooling structure or external cooling mode can be used to reduce the friction loss. High order harmonics will produce stray losses in windings and iron cores, which can improve stator windings and reduce the generation of high order harmonics. It can also be insulated on the surface of rotor grooves, and magnetic slot mud can be used to reduce the magnetic slot effect.