Adjustable speed motor is a kind of motor which can change the speed of motor by changing the series, voltage, current frequency of motor, so that the motor can achieve high performance.
There are many kinds of adjustable speed motors, among which asynchronous frequency conversion synchronous frequency conversion are two concepts that we often confuse. Today, I will tell you the differences similarities between them.
Asynchronous variable frequency motor is derived ordinary asynchronous motor. Because it needs to adapt to the characteristics of inverter output power, the motor has made great changes in rotor slot type, insulation technology, electromagnetic design verification, etc. Because the slip rate of asynchronous motor is determined by the manufacturing process of the motor, its discreteness is very large, the change of load directly affects the speed of the motor. To accurately control the speed of the motor, only the photoelectric encoder can be used for closed-loop control. When the single machine is controlled, the speed accuracy is determined by the number of pulses of the encoder. When the multi machine is controlled, the speed of multiple motors cannot be strictly synchronized 。
The rotor of synchronous variable frequency motor is inlaid with permanent magnet. When the motor is started in an instant, the motor turns into normal operation. The stator rotating magnetic field drives the rotor inlaid with permanent magnet for synchronous operation. At this time, the speed of the motor forms a strict corresponding relationship according to the sum of the motor the frequency of the motor input power supply. The speed is affected by the load other factors.
Due to the strict correspondence between the speed of the speed regulating motor the power frequency, the speed accuracy of the motor mainly depends on the accuracy of the output power frequency of the frequency converter. The control system is simple. The speed of multiple motors controlled by one frequency converter is the same, the optical encoder is needed for closed-loop control. The common point between them is that an independent forced cooling fan is added to adapt to the efficient heat dissipation of the motor at low speed reduce the wind friction of the motor at high speed.