What are the differences between brushless motor and brush motor - News & Events - Maxin Toos

Brushless motor: Brushless DC motor is composed of motor body and driver, and is a typical electromechanical integration product. Because the brushless DC motor operates in automatic control mode, it will not add additional starting winding on the rotor like the synchronous motor with heavy load starting under variable frequency speed regulation, nor will it generate oscillation and out-of-step when the load suddenly changes. The permanent magnets of small and medium capacity brushless DC motors now mostly use Nd-Fe-B materials with high magnetic energy level. Therefore, the volume of the rare earth permanent magnet brushless motor is reduced by one frame number compared with the three-phase asynchronous motor of the same capacity.

Brushless motor: A brush motor is a rotating motor that converts electrical energy into mechanical energy (motor) or mechanical energy into electrical energy (generator) with a brush device. Unlike brushless motors, brush devices are used to introduce or draw in voltage and current. Brushless motor is the foundation of all motors. It has the characteristics of fast starting, timely braking, smooth speed regulation in a large range, and relatively simple control circuit.

Brushless motor is the first type of motor that we are exposed to. It is also used as a model to show the motor introduced in physics class in middle school. The main structure of the brush motor is stator+rotor+brush. The rotating torque is obtained by rotating the magnetic field, thus outputting kinetic energy. The brush and the commutator are in constant contact and friction, and play the role of conducting electricity and commutation in rotation.

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, while the magnetic steel and carbon brush do not rotate. The alternating change of the coil current direction is completed with the motor's rotating commutator and brush.

In the brushless motor, this process is to arrange the two power input ends of each group of coils into a ring in turn, and separate them with insulating materials to form a cylinder-like thing, which is connected with the motor shaft. The power supply passes through two small columns (carbon brushes) made of carbon elements, and under the action of spring pressure, from two specific fixed positions, press two points on the upper coil power input ring cylinder, Energize a group of coils.

As the motor rotates, different coils or different poles of the same coil are energized at different times, so that the N-S pole of the magnetic field generated by the coil has a suitable angle difference from the N-S pole of the nearest permanent magnet stator. The magnetic field opposites attract and repel each other, generating force to drive the motor to rotate. The carbon electrode slides on the coil terminal like a brush on the surface of an object, so it is called a carbon "brush".

Sliding against each other will rub the carbon brush, causing loss, and the carbon brush needs to be replaced regularly; Alternating on and off between the carbon brush and the coil terminal will cause electric spark, electromagnetic damage and interference with electronic equipment.

In the brushless motor, the commutation is completed by the control circuit in the controller (generally Hall sensor+controller, the more advanced technology is magnetic encoder).

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 the brush motor are eliminated.

These circuits are motor controllers. The controller of the brushless motor can also achieve some functions that the brushless motor cannot achieve, such as adjusting the power switch angle, braking the motor, making the motor reverse, locking the motor, and stopping the power supply to the motor by using the brake signal. Now the electronic alarm lock of the battery car makes full use of these functions.

Brushless DC motor is composed of motor body and driver, which is a typical electromechanical integration product. Because the brushless DC motor operates in automatic control mode, it will not add additional starting winding on the rotor like the synchronous motor with heavy load starting under variable frequency speed regulation, nor will it generate oscillation and out-of-step when the load suddenly changes.

As early as the 19th century, when the motor was born, the practical motor was brushless, that is, AC squirrel-cage asynchronous motor, which was widely used after the generation of AC. However, the asynchronous motor has many insurmountable defects, resulting in the slow development of motor technology. In particular, the DC brushless motor has been unable to put into commercial operation. With the rapid development of electronic technology, it has not been put into commercial operation until recent years. In essence, it still belongs to the category of AC motor.

Brushless motor was invented shortly after its birth. Because of the simple structure of the DC brush motor, the production and processing are easy, the maintenance is convenient, and the control is easy; The DC motor also has fast response, large starting torque, and the performance of providing rated torque from zero speed to rated speed, so it has been widely used since it came out.

The DC brushless motor has fast starting response speed, large starting torque, stable speed change, almost no vibration from zero to the maximum speed, and can drive a larger load when starting. 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, accompanied by strong vibration, and the driving load is small when starting.

The speed of the brush motor is regulated by voltage, so the starting and braking are stable, and the operation at constant speed is also stable. Brushless motors are usually controlled by digital frequency conversion. First, AC is converted into DC, then DC is converted into AC, and the speed is controlled by frequency change. Therefore, brushless motors operate unevenly during starting and braking, with large vibration. Only when the speed is constant can they be stable.

The DC brushless motor is usually used together with the reducer and decoder to make the output power of the motor higher and the control accuracy higher. The control accuracy can reach 0.01 mm, which can make the moving parts stop at almost any desired place. All precision machine tools are controlled by DC motor. Brushless motor is unstable during starting and braking, so moving parts will stop at different positions every time. Only through locating pins or limiters can it stop at the desired position.

Due to the simple structure, low production cost, many manufacturers, and mature technology of DC brush motor, it is also widely used, such as factories, processing machines, precision instruments, etc. If the motor fails, it is only necessary to replace the carbon brush, and each carbon brush only costs a few yuan, which is very cheap. Brushless motor technology is not mature, its price is high, and its application range is limited. It should mainly be used in constant speed equipment, such as frequency conversion air conditioner, refrigerator, etc. Brushless motor damage can only be replaced.

Brushless motor removes the brush, and the most direct change is that there is no electric spark generated when the brush motor operates, which greatly reduces the interference of electric spark to remote control radio equipment.

Without the brush, the brushless motor will greatly reduce the friction during operation, run smoothly, and have much lower noise. This advantage is a huge support for the stability of the model operation.

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

In fact, the control of both types of motors is voltage regulation, but because brushless DC adopts electronic commutation, it can be realized only by digital control. Brushless DC is commutation 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 the brush motor is to adjust the power supply voltage of the motor. The adjusted voltage and current are converted through the commutator and brush to change the magnetic field generated by the electrode, so as to achieve the purpose of changing the speed. This process is called variable voltage speed regulation.

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