Compared with DC motors and asynchronous motors, the key technical features of brushless DC motors are:
1. Obtained similar operating characteristics of DC motor by electronic control, with good controllability and wide speed regulation range.
2. Rotor position feedback information and electronic multi-phase inverter drive are required.
3, in essence, the AC motor, because there is no spark and wear problems of the brush and the commutator, can work at high speed, can get higher reliability, long working life, no need for frequent maintenance.
4. The brushless DC motor has high power factor, no loss and heat generation of the rotor, and has high efficiency: compared with data, the efficiency of the 7.5kw asynchronous motor is 86.4%, and the efficiency of the same capacity brushless DC motor is 92.4%.
5, must have electronic control part, the total cost is higher than DC motor.
The electric motors used in the AC system mainly include two kinds of induction motors and permanent magnet synchronous motors. Among them, permanent magnet synchronous motors can be divided into sinusoidal back EMF permanent magnet synchronous motors (PMSM) and square waves according to different working principles. Back EMF Brushless DC Motors (BLDCM) have different drive currents and control methods due to different operating principles.
The back electromotive force of a sinusoidal permanent magnet synchronous motor is sinusoidal. To make the motor produce smooth torque, the current flowing in the motor winding must also be sinusoidal. It is necessary to know the continuous rotor position signal, and the inverter can This provides a sinusoidal voltage or current to the motor. Therefore, PMSM requires a high resolution position encoder or resolver, and the control algorithm is more complicated.
The back electromotive force of the brushless DC motor is trapezoidal. The motor winding only needs to input the square wave current, and the torque is straight. Therefore, the BLDCM does not need a high-resolution position sensor, the feedback device is simple, and the control algorithm is relatively simple. In addition, the air gap magnetic field of the BLDCM trapezoidal wave is higher than the air gap magnetic field of the PMSM sine wave, and the BLDCM has higher power density than the PMSM, and the output torque per unit volume is larger. Therefore, the application and research of permanent magnet brushless DC motors have received more extensive attention.
