In general, the rotor pole of BLDCM is made of tile type magnetic steel. After the magnetic circuit design, the air gap magnetic density of trapezoidal wave can be obtained. The stator winding mostly adopts concentrated whole pitch winding, so the induced back EMF is trapezoidal wave. The control of BLDCM needs the feedback of position information. It must have position sensor adopt the estimation technology of position sensor to form the automatic speed regulation system. During the control, the current of each phase is also controlled into square wave as far as possible. The output voltage of the inverter can be controlled according to the PWM method of the brush DC motor.
In essence, BLDCM is also a kind of permanent magnet synchronous motor, speed regulation actually belongs to the category of variable voltage variable frequency speed regulation.
Generally speaking, the permanent magnet synchronous motor has three-phase distributed stator winding permanent magnet rotor. In the magnetic circuit structure winding distribution, the induction electromotive force waveform is sinusoidal, the additional stator voltage current should also be sinusoidal, which is generally provided by the AC variable voltage converter. Permanent magnet synchronous motor control system usually adopts automatic control position feedback information. Advanced control strategies of vector control (field oriented control) direct torque control can be adopted.
The difference between them can be considered as the difference of design concept caused by square wave sine wave control.