Comparison of rare earth permanent magnet motors and asynchronous motors

<p>Synchronous motors, also called induction motors, whose excitation current is provided by the excitation weight of the stator (that is, the primary side of the transformer).</p><p><br></p><p>&nbsp;In order to achieve low speed, the number of poles needs to be set to the pole (usually greater than 20 poles).</p><p><br></p><p>The greater the number of motor poles, the greater the weight of the excitation current. For motors with more than 20 poles, the ratio of excitation current to active current is usually between 0.95:1 and 1.25:1, so the power factor is very low (0.62~0.72), and the drive capacity of the configuration is increased. As the current of the stator is increased a lot, the loss of the stator copper is very large, which greatly reduces the power of the motor.</p><p><br></p><p>Permanent magnet <a href="https://www.pm-motor.com/products" rel="noopener noreferrer" target="_blank"><a href="https://www.pm-motor.com/products" target="_blank">synchronous motor</a>s</a> 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 appropriately high (in theory, it can reach 1). Due to the extremely low reactive power of the stator current, the stator current is also significantly lower than the current of an asynchronous motor of the same amount and capacity. Especially in the case of a high-pole motor, the stator current may be 25% to 40%. Therefore, the copper loss of the stator is reduced by 30%. ~50%. Because the rotor has no current, it is different from the asynchronous motor. The rotor has current, causing loss, which usually accounts for 30% of the total loss of the asynchronous motor. Therefore, the total loss of permanent magnet synchronous motors is generally 40% to 60% lower than that of asynchronous motors. Because the elevator<a href="https://www.pm-motor.com/products" rel="noopener noreferrer" target="_blank"> <a href="https://www.pm-motor.com/products" target="_blank">permanent magnet motor</a></a> with high remanence magnetic induction and high coercivity NdFeB data and high energy density has been completely selected, the air gap magnetic density will usually reach 0.75T (Tesla) or more, which makes the volume and The weight is 30% to 40% smaller than asynchronous motors.</p>