Permanent magnet synchronous motors consist of a stator, rotor, and permanent magnets. The stator windings generate a rotating magnetic field, and the rotor's permanent magnet magnetic field rotates synchronously with it. Its working principle is based on electromagnetic induction and the Lorentz force, achieving speed regulation through precise control of the stator current. Compared to traditional asynchronous motors, it eliminates the rotor coil structure, reducing excitation losses.
Classification by Excitation Current Supply Method
Permanent magnet synchronous motors utilize permanent magnets to establish an excitation magnetic field. The stator generates a rotating magnetic field, and the rotor is made of permanent magnet material. Synchronous motors require a DC magnetic field to achieve energy conversion; the DC current that generates this magnetic field is called the motor's excitation current.
Separately Excited Motors: Motors that obtain their excitation current from other power sources.
Self-Excited Motors: Motors that obtain their excitation current from within the motor itself.
Classification by Power Supply Frequency
Permanent magnet brushless motors include two types: permanent magnet brushless DC motors and permanent magnet brushless AC motors. Both require frequency converters for operation. The former only requires a square-wave inverter for power supply, while the latter requires a sinusoidal-wave inverter.
Classification by Air Gap Magnetic Field Distribution:
Sinusoidal Permanent Magnet Synchronous Motor: The magnetic poles use permanent magnet materials. When a three-phase sinusoidal current is input, the air gap magnetic field is distributed according to a sinusoidal law. This is simply called a permanent magnet synchronous motor.
Trapezoidal Permanent Magnet Synchronous Motor: The magnetic poles are still made of permanent magnet materials, but when a square wave current is input, the air gap magnetic field exhibits a trapezoidal wave distribution. Its performance is closer to that of a DC motor. Self-controlled variable frequency synchronous motors constructed using trapezoidal wave permanent magnet synchronous motors are also known as brushless DC motors.