Explain the difference between brushed motors and brushless motors

Brief introduction of brush motor and brushless motor

　　1, brush motor

　　 It uses carbon brushes as the two contacts of the motor power supply, and is controlled by the speed control knob and the controller. The electric bicycle can achieve 0-20 km/h stepless speed regulation through the secondary gear reduction and overrunning clutch. The brushed high-speed motor currently used has high gold content, strong reduction gear strength, good wear resistance and reasonable design, so the repair rate is low; and the cost of repairing and replacing gears and motors is less, which effectively reduces the electric bicycle The maintenance cost; and the brush motor can realize easy manual riding through the overrunning clutch and flywheel. Brushed motors use brush mechanical commutation!

　　2, brushless motor

　　The cost of its speed control system is higher than that of a brushed high-speed motor, and the controller is prone to failure during use. Electric bicycles equipped with brushless motors must run at a speed of 35 km/h or more to give full play to their best work efficiency. However, we know that electric bicycles are managed as non-motorized vehicles and the speed must be below 20 km/h. The selection of brushless motors by electric bicycles reduces work efficiency and is not highly desirable. The main point it is used now is low noise. The brushless motor uses electronic circuit commutation! There is a detection element to detect polarity!

Detailed explanation of the difference between brush motor and brushless motor

　　 1. The difference of speed regulation

In fact, the control of the two motors is voltage regulation, but because the brushless DC adopts electronic commutation, it can only be realized by digital control, while the brushless DC is commutated by carbon brushes, using thyristors, etc. Traditional analog circuits can be controlled and are relatively simple.

　　 1. The process of brush motor speed adjustment is to adjust the voltage of the motor power supply. The adjusted voltage and current are converted by the commutator and the brush to change the strength of the magnetic field generated by the electrode to achieve the purpose of changing the speed. This process is called variable voltage speed regulation.

　　2. In the process of brushless motor speed regulation, the voltage of the power supply of the motor is unchanged, the control signal of the ESC is changed, and the switching rate of the high-power MOS tube is changed through the microprocessor to realize the change of the speed. This process is called variable frequency speed regulation.

　　 2. Performance difference

　　 1. The brush motor has simple structure, long development time and mature technology

　　 When the motor was born as early as the 19th century, the practical motor produced was a brushless form, that is, an AC squirrel cage asynchronous motor. This motor has been widely used after the generation of AC power. However, asynchronous motors have many insurmountable shortcomings, resulting in slow motor technology development. In particular, brushless DC motors have not been able to be put into commercial operation. With the rapid development of electronic technology, they have not been put into commercial operation until recent years. In essence, they still belong to the category of AC motors.

　　 Shortly after the birth of the brushless motor, people invented the DC brushed motor. Because the DC brush motor has simple mechanism, easy production and processing, convenient maintenance and easy control; DC motor also has fast response, large starting torque, and can provide rated torque performance from zero speed to rated speed, so once it came out It has been widely used.

　　2, DC brushed motor has fast response speed and large starting torque

　　 The DC brushed motor has fast starting response speed, large starting torque, stable speed change, almost no vibration from zero to maximum speed, and 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, 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, DC brush motor control accuracy is high

　　 DC brushed 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, which can almost stop moving parts wherever you want. All precision machine tools adopt DC motors to control precision. Because the brushless motor is not stable when starting and braking, the moving parts will stop at a different position each time, and the positioning pin or stopper must be used to stop at the desired position.

　　5. The DC brush motor has low cost and easy maintenance. Because of the simple structure of the DC brush motor, the low production cost, the large number of manufacturers and the mature technology, it is also widely used, such as factories, processing machine tools, precision instruments, etc. If the motor fails, only the carbon brushes need to be replaced. Carbon brushes only cost a few yuan, which is very cheap. The brushless motor technology is immature, the price is high, and the application range is limited. It should be 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. 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.

　　7, low noise, smooth operation

　　 The brushless motor has no brushes, the friction is greatly reduced during operation, the operation is smooth, and the noise is much lower. This advantage is a huge support for the stability of the model.

　　 8. Long life, low maintenance cost

　　 Without the brush, the wear of the brushless motor is mainly on the bearing. From a mechanical point of view, the brushless motor is almost a maintenance-free motor. When necessary, only need to do some dust removal maintenance.