The DC (brush) motor can adjust speed by adjusting voltage, connecting resistance in series and changing excitation, but it is more convenient and more commonly used to adjust voltage

At present, DC motors mainly use PWM for speed regulation. PWM actually realizes DC voltage regulation through high-speed switch. Within a cycle, the average voltage will be high if the switch is turned on for a long time, and the average voltage will be low if the switch is turned off for a long time. It is very convenient to adjust. As long as the switch speed is fast enough, there will be less harmonic in the grid and the current will be more continuous. But the brush and commutator are worn for a long time, and there is a huge current change during commutation, which is very easy to produce sparks. The commutator and brush limit the capacity and speed of the DC motor, making the speed regulation of the DC motor encounter a bottleneck. For the brushless DC motor, only the input voltage is controlled on the surface when the speed is adjusted, but the automatic variable frequency speed control system of the motor (the brushless DC motor itself is equipped with a rotor position signal acquisition device such as a rotor position detector, and the rotor position signal of this device is used to control the commutation time of the variable voltage variable frequency speed control device) automatically controls the frequency according to the variable voltage, which is almost the same as that of the DC (brushless) motor, and is very convenient to use. Because the rotor adopts permanent magnet, without special excitation winding, under the same capacity, the motor has smaller volume, lighter weight, higher efficiency, more compact structure, more reliable operation and better dynamic performance, and has been widely used in the drive of electric vehicles.

Hangzhou Jizhi has developed a number of motor rotor dynamic balancing machines. The following brushless motor rotor balancing machine is applicable to the dynamic balancing correction of brushless motor rotor with an outer diameter of less than 40mm. It can automatically measure, automatically correct, and automatically optimize the dynamic balancing parameters, with high accuracy and effectively improve the production efficiency.