1、 The principle of brushed motor

Brushed motors use mechanical commutation, with magnetic poles stationary and coils rotating. When the motor is working, the coil and commutator rotate, while the magnet and carbon brush do not rotate. The alternating change in the direction of the coil current is completed by the inverter and brush that rotate with the motor.

In a brushed motor, this process involves arranging the two power input terminals of each group of coils in a ring, separating them with insulating material to form a cylindrical object that is connected to the motor shaft. The power supply is powered by two small carbon pillars (carbon brushes) made of carbon elements, which are pressed from two specific fixed positions on the circular cylinder of the coil power input under the action of spring pressure, to energize a group of coils.

As the motor rotates, different coils or different poles of the same coil are energized at different times, creating a suitable angle difference between the N-S pole of the magnetic field generated by the coil and the N-S pole of the nearby permanent magnet stator. The magnetic fields attract each other and repel each other, generating force that drives the motor to rotate. The carbon electrode slides on the coil connector, like a brush brushing on the surface of an object, hence it is called a carbon "brush".

Sliding against each other will cause friction on the carbon brush, resulting in wear and tear, requiring regular replacement of the carbon brush; Alternating on-off connections between carbon brushes and coil terminals can generate electrical sparks, electromagnetic waves, and interfere with electronic devices.

2、 Working principle of brushless motor

The brushless motor adopts electronic commutation, with the coil stationary and the magnetic poles rotating. Brushless motor is a set of electronic devices that use Hall elements to sense the position of permanent magnet poles. Based on this perception, electronic circuits are used to timely switch the direction of current in the coil, ensuring the generation of magnetic force in the correct direction to drive the motor. Eliminating the drawbacks of brushed motors.

These circuits are motor controllers. The controller of a brushless motor can also achieve some functions that cannot be achieved by a brushed motor, such as adjusting the power switching angle, braking the motor, reversing the motor, locking the motor, and using the brake signal to stop supplying power to the motor. The electronic alarm lock of electric bicycles now fully utilizes these functions.

Brushless DC motor consists of a motor body and a driver, and is a typical electromechanical integrated product. Due to the self controlled operation of brushless DC motors, they do not require additional starting windings on the rotor like synchronous motors that start under heavy loads under variable frequency speed regulation, nor do they produce oscillations and loss of step during sudden load changes.

3、 Differences in speed regulation methods

In fact, the control of both types of motors is voltage regulation, but due to the electronic commutation used in brushless DC, digital control is required to achieve it, while brushed DC is controlled through carbon brush commutation using traditional analog circuits such as thyristors, which is relatively simple.

1. The speed regulation process of a brushed motor is to adjust the voltage of the motor power supply. The adjusted voltage and current are converted through rectifiers and brushes to change the strength of the magnetic field generated by the electrodes, achieving the goal of changing the rotational speed. This process is called variable voltage speed regulation.

2. The speed regulation process of a brushless motor involves keeping the voltage of the motor's power supply constant, changing the control signal of the electric regulator, and then adjusting the switching rate of the high-power MOS transistor through a microprocessor to achieve a change in speed. This process is called variable frequency speed regulation.

4、 Performance differences

1. Brushed motors have a simple structure, long development time, and mature technology

As early as the 19th century, when the electric motor was born, the practical motor produced was the brushless form, namely the AC squirrel cage asynchronous motor. This type of motor has been widely used after the generation of AC power. However, asynchronous motors have many insurmountable defects, resulting in slow development of motor technology. Especially, brushless DC motors have been unable to be put into commercial operation. With the rapid development of electronic technology, DC motors have only gradually been put into commercial operation in recent years, and in essence, they still belong to the category of AC motors.

Not long after the birth of brushless motors, people invented DC brushed motors. Due to the simple mechanism, easy production and processing, convenient maintenance, and easy control of DC brushed motors; DC motors also have fast response, large starting torque, and the ability to provide rated torque from zero speed to rated speed, so they have been widely used since their inception.

2. DC brushed motor has fast response speed and high starting torque

DC brushed motors have fast starting response speed, high starting torque, smooth speed change, and almost no vibration when the speed ranges from zero to * * *. They can drive larger loads during starting. Brushless motors have high starting resistance (inductance), so the power factor is small, the starting torque is relatively small, there is a buzzing sound and strong vibration during starting, and the load driven during starting is small.

3. DC brushed motor runs smoothly and has good starting and braking effects

Brushed motors are regulated by voltage and speed, so they start and brake smoothly, and also run smoothly at constant speed. Brushless motors are usually controlled by digital frequency conversion, which first converts AC to DC and then DC to AC, and controls the speed through frequency changes. Therefore, brushless motors operate unstably and vibrate greatly during starting and braking, and only stabilize when the speed is constant.

4. DC brushed motor has high control accuracy

DC brushed motors are usually used together with gearboxes and decoders to increase the output power of the motor and improve control accuracy. The control accuracy can reach 0.01 millimeters, allowing moving parts to stop almost anywhere they want. All precision machine tools use DC motors to control accuracy. Due to the instability during start-up and braking, the moving parts of a brushless motor will stop at different positions every time, and must be stopped at the desired position through positioning pins or limiters.

5. DC brushed motors have low operating costs and are easy to maintain. Due to the simple structure, low production cost, multiple manufacturers, and mature technology of DC brushed motors, they are widely used in factories, machining machines, precision instruments, etc. If the motor fails, only the carbon brush needs to be replaced, and each carbon brush only costs a few yuan, which is very cheap. Brushless motor technology is immature, expensive, and has limited application scope. It should mainly be used in constant speed equipment, such as variable frequency air conditioners, refrigerators, etc. If the brushless motor is damaged, it can only be replaced.

6. Brushless, low interference

The brushless motor removes the electric brush, and the direct change is that there is no electric spark generated during the operation of the brushed motor, which greatly reduces the interference of electric sparks on remote control radio equipment.

7. Low noise, smooth operation

Brushless motors without electric brushes greatly reduce friction during operation, resulting in smooth operation and much lower noise. This advantage is a huge support for the stability of model operation.

8. Long lifespan, low maintenance cost

Without electric brushes, the wear of brushless motors is mainly on the bearings. From a mechanical perspective, brushless motors are almost maintenance free motors, and when necessary, only some dust removal maintenance is needed.