1. The motor body of the medium-sized DC permanent magnet 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 disk;
3. Different control:
Medium-sized DC permanent magnet motor: 120 degree square wave current, using PWM control;
Permanent magnet synchronous motor: Sine wave current, SPWM SVPWM control.
Medium-sized DC permanent magnet motor: The magnet is magnetized by a square wave, the control voltage PWM is also a square wave, and the current is also a square wave. There are 6 space vectors in one electrical cycle. The control is simple, the cost is low, and the general MCU can be realized.
Permanent magnet synchronous motor: The magnet is magnetized by a sine wave, the back electromotive force is also a sine wave, and the current is also a sine wave. Vector control technology is generally used, and there are generally at least 18 vectors in an electrical cycle (of course, the more the better), which can be realized by a high-performance MCU or DSP.
DC Servo: This range is very wide. DC servo refers to the control of the DC motor and then the control system, according to the control instructions (speed, position, angle, etc.) to act, generally used for actuators.
1. The difference of sensors:
Medium-sized DC permanent magnet motor (BLDC): position sensor, such as Hall, etc.;
Permanent magnet synchronous motor (PMSM): speed and position sensors, such as resolvers, photoelectric encoders, etc.;
2. The back EMF waveform is different:
BLDC: approximate trapezoidal wave (ideal state);
PMSM: Sine wave (ideal state
Three, the phase current waveform is different:
BLDC: approximate square wave or trapezoidal wave (ideal state);
PMSM: Sine wave (ideal state
Fourth, the difference between the control system:
BLDC: usually includes position controller, speed controller and current (torque) controller;
PMSM: Different control strategies will have different control systems;
5. The difference between design principles and methods:
BLDC: widen the width of the back-EMF waveform as much as possible (make it approximate to a ladder wave);
PMSM: Make the back EMF close to the sine wave;
Reflected in the design is mainly the difference in stator winding and rotor structure (such as pole arc coefficient).
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Post time: Aug-20-2021