1. An asynchronous motor, also known as an induction motor, has an excitation current that is provided by the excitation weight of the stator (that is, the primary side of the transformer).
2. In order to reach low speed, the demand is made into a high number of poles (generally greater than 20 poles).
3. The more the number of motor poles, the greater the excitation current weight. For motors larger than 20 poles, the ratio of excitation current to active current is generally between 0.95:1 and 1.25:1, so the power factor is very low (0.62~ 0.72), and the configured drive capacity is also added. Because the stator current of the composition is added a lot, the loss of the stator copper is large, which greatly reduces the power of the motor.
Permanent magnet synchronous motors do not require stator ratings to provide excitation current because their excitation is done by permanent magnets. Therefore, the power factor of the motor can be made appropriately high (in theory, it can reach 1). Since the stator current is extremely low in reactive power, the stator current is also significantly lower than that of the same-number, same-capacity asynchronous motor, especially in the case of high-pole motors, which can be 25% to 40% smaller, thus reducing the copper loss of the stator by 30%. ~50%. Because the rotor has no current, so unlike the asynchronous motor, the rotor has current, resulting in loss, which is generally 30% of the total loss in the asynchronous motor. Therefore, the total loss of the permanent magnet synchronous motor is generally 40% to 60% lower than that of the asynchronous motor. Because the permanent magnet motor for elevators is now fully selected with high remanence magnetic induction and high coercivity NdFeB data with high energy density, the air gap magnetic density generally reaches above 0.75T (Tesla), making the volume of the motor and The weight can be 30% to 40% smaller than the asynchronous motor.