Many friends like to compare brushless motors with brushed motors. For example, in terms of speed, people often ask: Is the speed of brushed motors higher than that of brushless motors? How to explain? I have to analyze it in detail:

If you only compare it in terms of speed, there is no comparison. Brushless motors are developed on the basis of brushed motors with the help of power electronics technology; brushless motors are divided into permanent magnet types and brushless excitation types. Brushless motors generally refer to permanent magnet types, called permanent magnet DC brushless motors. If it is used as a generator, it generally refers to the excitation type and is called a brushless generator. The brushed motor is electric excitation, which is divided into series excitation and other excitation.

Motor speed is determined by motor voltage and air gap flux linkage. The air-gap flux linkage is the product of the air-gap flux and the number of turns in the coil. Theoretically, if the voltage is the same, as long as the air gap flux linkage adjustment is the same, the speed of the two will be the same. But in fact, since the permanent magnet brushless DC motor is made of permanent magnets, the magnetic steel is on the surface of the rotor, and the magnetic flux cannot be changed, so the maximum speed of a motor is fixed after forming, and the air gap magnetic The chain cannot be changed by the controller, or the change is small.

Therefore, once the voltage and maximum torque of the brushless DC motor are determined, the designed motor speed is fixed and cannot be increased (unless the controller has a boost function), which is why the application of the brushless DC motor is limited. The brushed motor is different, because it is electric excitation, the excitation current can be reduced through the controller, thereby reducing the air gap flux linkage and increasing the speed. In this sense, the rotational speed of a brushed motor is higher than that of a brushless motor. Brushless motors and brushed motors have their own advantages, depending on the application.

If the permanent magnet motor has magnetic steel embedded in the rotor core, the controller can realize the function of weakening the magnetic field, adjust the positive gap flux linkage, increase the speed, and reach the same speed as the brushed motor. It is not said that the speed is lower than that of a brushed motor, but this kind of motor is generally not called a brushless motor, but a permanent magnet synchronous motor, or more accurately, a permanent magnet synchronous reluctance motor.

The above is the knowledge of the speed of brushless motors and brushed motors. Which one is faster depends on the specific situation.