The difference in principle: the brush motor adopts mechanical commutation, the magnetic pole does not move, and the coil rotates. When the motor is working, the coil and commutator rotate, but the magnetic steel and carbon brushes do not rotate. The alternating current direction of the coil is changed by the commutator and brushes that rotate with the motor. The brushless motor adopts electronic commutation, the coil does not move, and the magnetic pole rotates.
Second, the difference in speed regulation methods: in fact, the control of the two motors is voltage regulation, but because the brushless DC uses electronic commutation, it can only be realized with digital control, while the brushless DC is replaced by carbon brushes. It can be controlled by traditional analog circuits such as thyristor, which is relatively simple.
Three, the difference in performance difference:
1. The brush motor has simple structure, long development time and mature technology:
As early as when the motor was born in the 19th century, the practical motor produced was a brushless form, that is, an AC squirrel cage asynchronous motor. This kind of motor has been widely used after the generation of AC. However, asynchronous motors have many insurmountable shortcomings, so that the development of motor technology is slow.
2. The DC brushed motor has fast response speed and large starting torque:
The DC brushed motor has a fast starting response speed, large starting torque, stable speed change, and almost no vibration is felt from zero to maximum speed, which can drive a larger load when starting. 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 buzzing sound when starting, and accompanied by strong vibration, the load is small when starting.
3. The DC brushed motor runs smoothly, with good starting and braking effects:
The brush motor is speed-regulated by voltage regulation, so the starting and braking are stable, and it is also stable when running at a constant speed. Brushless motors are usually controlled by digital frequency conversion. First, the AC becomes DC, then DC becomes AC, and the speed is controlled by frequency change. Therefore, the brushless motor does not run smoothly when starting and braking, and the vibration is large, only when the speed is constant. Will be stable.
4. High control precision of DC brushed motor:
Brushed DC motors are usually used together with gearboxes and encoders to make the motor output more power and control accuracy. The control accuracy can reach 0.01 mm, and the moving parts can be stopped almost wherever they want. All precision machine tools adopt DC motors to control precision.
5. The use cost of the DC brush motor is low, and the maintenance is convenient:
Due to the simple structure of the DC brush motor, the low production cost, the large number of manufacturers and the more mature technology, the application is also relatively wide and very cheap. The brushless motor technology is immature, the price is high, and the application range is limited. It is mainly used in constant speed equipment, such as inverter air conditioners and refrigerators. The brushless motor can only be replaced if it is damaged.
6. No brush, low interference:
The brushless motor removes the brush, and the most direct change is that there is no electric spark generated when the brush motor is running, which greatly reduces the interference of the electric spark to the remote control radio equipment.
