When the motor is working, the coil and the commutator rotate, the magnetic steel and the carbon brush do not rotate, and the alternating change of the coil current direction is completed by the commutator and the brush that rotate with the motor. The brushless motor adopts electronic commutation, the coil does not move, and the magnetic pole rotates.
The difference between the speed control modes: In fact, the control of the two motors is voltage regulation, but since the brushless DC adopts electronic commutation, digital control can be realized, and the brush DC is commutated by the carbon brush. It can be controlled by traditional analog circuits such as thyristors, which is relatively simple.
Differences in performance differences:
1. The brush motor has a simple structure, long development time and mature technology
2. The DC brush motor has a fast response speed and a large starting torque: The DC brush motor has a fast starting response speed, a large starting torque, a stable shifting speed, almost no vibration from zero to maximum, and a larger load at the start. The brushless motor has a large starting resistance (inductive reactance), so the power factor is small, the starting torque is relatively small, there is a click when starting, and accompanied by strong vibration, the load is small when starting.
3. The DC brush motor runs smoothly, and the starting and braking effects are good: The brush motor is regulated by voltage regulation, so the starting and braking are stable, and it is stable even at a constant speed. The brushless motor is usually digital frequency conversion control. It first turns the alternating current into direct current, the direct current becomes alternating current, and the speed is controlled by the frequency change. Therefore, the brushless motor runs unevenly during starting and braking, and the vibration is large, only when the speed is constant. Will be smooth.
4. DC brush motor control accuracy: The DC brush motor is usually used together with the reduction gearbox and the decoder to make the motor have higher output power, higher control precision, and the control precision can reach 0.01 mm, which can almost move the moving parts to any desired place. All precision machine tools use DC motor control accuracy.