The structure of hub motor can be divided into brushless motor and brushless motor. At first, the hub motor used brush motor, but later, because of the low efficiency of brush motor, most of the hub motor on the market use brushless motor. You may have doubts about the difference between the two types of motors. Today's small series of global wind turbines will take you to understand the difference between brushless and brushless motors.
1、 The working principle is different
For hub motor, the output mode of motor torque is different, and whether it is decelerated by gear reducer, its mechanical structure is also different.
1. There is a rotating motor with rotating coil. When the motor works, the coil and the commutator rotate, while the magnetic steel and carbon brush do not rotate. The alternating change of coil current direction is completed by the commutation and brush rotating by the motor.
2. The working principle of brushless motor adopts electronic commutation, the coil does not move and the magnetic pole rotates. Brushless motor uses a set of electronic equipment to sense the position of permanent magnet magnetic pole through Hall element. According to this perception, electronic circuit is used to timely switch the direction of current in the coil to ensure that the magnetic force in the correct direction is generated to drive the motor. The disadvantages of brush motor are eliminated.
2、 Performance differences
1. Energy saving
Generally speaking, because there is no friction loss of mechanical commutation, gearbox consumption and speed control circuit loss of Brushless DC motor, the efficiency is usually higher than 85%. However, considering the cost performance ratio in the actual design, in order to reduce the material consumption, the general design is 76%. However, the efficiency of brush DC motor is usually about 70% due to the consumption of gearbox and overrunning clutch.
2. Starting and braking
The speed of brush motor is regulated by voltage regulation, so the starting and braking are stable, and the operation at constant speed is also stable. Brushless motor is usually controlled by digital frequency conversion, which changes AC into DC, DC and then AC. the speed is controlled by frequency change. Therefore, the brushless motor runs unsteadily and vibrates heavily when starting and braking, and it will be stable only when the speed is constant.
3. Control accuracy
DC brush motor is usually used together with reducer and decoder, so that the output power of the motor is greater and the control precision is higher. The control accuracy can reach 0.01 mm, which can make the moving parts stop at any place you want. All precision machine tools use DC motor to control precision. Because the brushless motor is not smooth when starting and braking, the moving parts will stop at different positions every time. It is necessary to stop at the desired position by positioning pin or limiter.
4. Noise
Without the brush, the friction force of brushless motor is greatly reduced, which greatly reduces the interference of electric spark on remote control radio equipment, and the noise will be much lower. This advantage is a great support for the operation stability of hub motor.
3、 The scope of application is different
Brushless motor is usually used in the equipment with high control requirements and high speed, such as aircraft model, precision instruments, etc., which have strict control on motor speed and reach high speed. The cost of motor and controller is very high, so high-end equipment is used later.
Generally, brush motors are used in power equipment, such as hair dryer, factory motor, household range hood and so on. In addition, the rotation speed of series excitation motor can reach high, but the wear rate of carbon brush is relatively high.
4、 Difference of speed regulation mode
In fact, the control of the two kinds of motors is voltage regulation. Only because the brushless DC adopts electronic commutation, it can be realized by digital control. The brushless DC is commutating through carbon brush, and can be controlled by traditional analog circuits such as silicon controlled rectifier, which is relatively simple.
1. The speed regulation process of brush motor is to adjust the voltage of motor power supply. After adjusting the voltage and current through commutator and brush to ground conversion, change the magnetic field generated by the electrode, to achieve the purpose of changing the speed. This process is called variable voltage speed regulation.
2. The speed control process of brushless motor is that the voltage of the power supply of the motor remains unchanged, the control signal of the electric regulator is changed, and the switch speed of the high-power MOS transistor is changed by the microprocessor to realize the change of the speed. This process is called frequency control.
5、 Different service life
The service life of brushless motor is usually in the order of tens of thousands of hours, but due to the different bearings, the service life of brushless motor is also very different. Usually, the continuous working life of brush motor is in hundreds to 1000 hours. When the service limit is reached, it is necessary to replace the carbon brush, otherwise it is easy to cause bearing wear.
6、 Maintenance
The carbon brush motor needs to be replaced. If the carbon brush is not replaced in time, the motor will be damaged. However, the service life of the brushless motor is very long, which is usually more than 10 times of that of the brush motor. It is almost a maintenance free motor. If necessary, just do some dust removal maintenance. But it's broken and needs to be replaced.
Through the above analysis, we can clearly see the difference between the brushless motor and the brushless motor in the structure of the hub motor. Generally speaking, the brushless motor is better than the brush motor in all aspects, so it gradually becomes the mainstream of the hub motor structure.
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