Analysis of Brushless DC Motor and Synchronous Motor

Update:19 Apr 2021

Comparison and Analysis of Permanent Magnet Brushless D […]

Comparison and Analysis of Permanent Magnet Brushless DC Motor and Permanent Magnet Synchronous Motor

The difference between the two can be considered to be the different design concepts caused by the square wave and sine wave control.

Finally, correct a concept, "DC frequency conversion" is actually AC frequency conversion, but the control object is usually called "brushless DC motor"

In my understanding, it should be said that the difference between BLDC and PMSM is really hard to tell, sometimes it depends on the application. The traditional saying is that their back EMF is different, BLDC is close to a square wave, PMSM is close to a sine wave. In terms of control, BLDC generally uses a 6-beat square wave drive to control the phase and reverse time of the square wave, and PMSM uses FOC. In terms of performance, the output power density of the BLDC will be larger, because the torque of the BLDC makes full use of the harmonics, and therefore the harmonics of the BLDC will be more serious

1. The motor body of the brushless DC motor:

The stator winding is a concentrated winding, and the permanent magnet rotor forms a square wave magnetic field; the motor body of a permanent magnet synchronous motor: the stator winding is a distributed winding, and the permanent magnet rotor forms a positive mysterious magnetic field;

2. Position sensor of brushless DC motor:

Low resolution, 60 degree resolution, Hall element, electromagnetic type, photoelectric type; Position sensor of permanent magnet synchronous motor: high resolution, 1/256, 1/1024, resolver, optical code disc;

3. Different control:

Brushless DC motor: 120 degree square wave current, using PWM control;

Permanent magnet synchronous motor: Sine wave current, SPWM SVPWM control.