The difference between brush motor and brushless motor

Brushed motors are the first type of motor that everyone comes into contact with, such as many electric small toys or many household hair dryers. The main structure of a brush motor is the stator, rotor, and brush. The rotating torque is obtained through the rotating magnetic field to output kinetic energy. The brush and commutator constantly come into contact and friction, playing a conductive and commutative role in rotation.

In a brushless motor, this process involves arranging the two power input terminals of each group of coils into a ring, separated by insulating materials, to form a cylindrical object that is connected to the motor shaft. The power is supplied through two small pillars (carbon brushes) made of carbon elements, and under the action of spring pressure, it is pressed onto the two points on the circular cylinder of the coil power input from two specific fixed positions, Energize a set of coils.

As the motor rotates, different coils or different poles of the same coil are energized at different times, resulting in a suitable angle difference between the N-S pole of the coil that generates the magnetic field and the N-S pole of the nearest permanent magnet stator. The magnetic field attracts and repels each other, generating force and driving the motor to rotate. The carbon electrode slides on the wire terminal of the coil, like a brush brushing on the surface of an object, so it is called a carbon "brush". Sliding against each other can cause friction and wear on the carbon brushes, requiring regular replacement of the brushes; Alternating on and off between the carbon brush and the coil terminal can cause electric sparks, electromagnetic damage, and interference with electronic devices.

Brushless DC motor is a typical mechatronics product composed of the motor body and driver. The rotor of a brushless motor is made of permanent magnet steel, which is connected to the output shaft along with the casing. The stator is a winding coil, which removes the commutating brush used by the brush motor to alternately transform the electromagnetic field. Therefore, it is called a brushless motor. By changing the alternating frequency and waveform of the current wave input to the stator coil of the brushless motor, a magnetic field rotating around the geometric axis of the motor is formed around the winding coil, This magnetic field drives the permanent magnet steel on the rotor to rotate, and the motor starts to rotate. The performance of the motor is related to factors such as the number of magnetic steel, magnetic flux strength, and input voltage of the motor. It is also closely related to the control performance of the brushless motor, as the input is direct current, which needs to be converted into 3 alternating currents by an electronic governor. It also needs to receive control signals from the remote control receiver to control the motor speed, To meet the needs of model usage.

Brushless motors adopt electronic commutation, with the coil stationary and the magnetic poles rotating. The position of the rotor of a brushless motor can be determined through Hall elements, encoders, or other means to sense the position of the permanent magnet poles. Based on this perception, the direction of the current in the coil can be timely switched to ensure the generation of the correct magnetic force to drive the motor. These circuits are motor controllers. The controller of a brushless motor can also achieve some functions that cannot be achieved by a brushless motor, such as adjusting the power switching angle, braking the motor, reversing the motor, locking the motor, and using the braking signal to stop power supply to the motor. The electronic alarm lock of electric vehicles now fully utilizes these functions.

Due to the self controlled operation of brushless DC motors, they do not add additional starting windings to the rotor like synchronous motors that start with heavy loads under variable frequency speed regulation, nor do they generate oscillations and out of step during sudden load changes.

Brushed motors: Usually, power equipment uses brushed motors, such as hair dryers, factory motors, household range hoods, etc. However, due to the wear and tear of carbon brushes, regular replacement of brushes is required, resulting in the lifespan of brushed motors.

Brushless motor: Usually used on equipment with high control requirements and high speed, such as aircraft models, precision instruments, etc., which strictly control the motor speed and achieve high speed.

Brushed motor: The carbon electrode slides on the coil terminal, and the N-S pole of the coil that generates the magnetic field has a suitable angle difference from the N-S pole of the nearest permanent magnet stator. The magnetic field attracts and repels each other, generating force to drive the motor to rotate. It is relatively simple to directly control the speed by adjusting the size of the power supply voltage.

Brushless motor: Brushless motor senses the position of the permanent magnet poles through Hall elements, encoders, or other means. Based on this perception, it timely switches the direction of the current in the coil to ensure the correct direction of magnetic force is generated to drive the motor. Generally, the voltage of the power supply remains unchanged, and the control signal of the electrical regulator is changed. The microprocessor then changes the switching speed of the high-power MOS transistor to achieve a change in speed.

Brushed motor: The motor has fast response speed, high starting torque, and almost no vibration can be felt from zero to maximum speed. It can drive a larger load during starting.

Brushless motor: Due to high starting resistance (impedance), the power factor is low. Digital frequency conversion control is used to convert DC into AC, and the speed is controlled through frequency changes. Therefore, the brushless motor runs unevenly during starting and braking, with relatively small starting torque and buzzing noise accompanied by strong vibration. The load is small during starting, and the vibration is large. It only stabilizes when the speed is constant.

DC brushless motors are usually used together with gearboxes and decoders, resulting in higher output power and 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. Brushless motors are unstable during startup and braking, so the moving parts always stop at different positions. They must be stopped at the desired position through positioning pins or limiters.

Brushless motors can timely switch the direction of current in the coil based on the actual rotor position, ensuring maximum torque generation at all times even under different loads. However, the commutation of brushless motors can only be determined by the brushes and there is friction loss. Therefore, relatively speaking, brushless motors controlled by variable frequency technology will save much more energy than brushless motors, the most typical of which are variable frequency air conditioners and refrigerators.

The carbon brush motor needs to be replaced, and if not replaced in a timely manner, it can cause damage to the motor. Brushless motors have a long service life, usually more than 10 times that of brush motors. However, if the motor is damaged, it needs to be replaced, but daily maintenance is basically unnecessary.

Brushless motors remove the brushes, and the most direct change is the absence of electric sparks generated during the operation of brush motors, which greatly reduces the interference of electric sparks on remote control radio equipment.

Brushless motors without brushes greatly reduce friction during operation, operate smoothly, and have much lower noise. This advantage provides a huge support for the stability of model operation.