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2023

Permanent magnet synchronous motor

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The structure of a permanent magnet synchronous motor includes a stator, a rotor, a motor shaft, front and rear bearings, end covers, cooling water channels, position sensors, temperature sensors, low-voltage wiring harnesses and power wiring harnesses. The stator is composed of a stator core and a three-phase winding; the rotor is composed of permanent magnet poles and a core, and the core is laminated with silicon steel sheets. According to the arrangement of permanent magnets in the rotor, it mainly includes a surface convex permanent magnet rotor, a surface embedded permanent magnet rotor and an internal permanent magnet rotor. At present, a new energy motor commonly uses an internal permanent magnet rotor. (Figure 4)

Working principle of 2.2 permanent magnet synchronous motor

2.2.1 Driving principle of permanent magnet synchronous motor

The rotating magnetic field is provided by the stator, and the magnetic field is generated in the same way and at the same speed as the AC asynchronous motor. The magnetic poles are provided by the rotor permanent magnets. In this way, the rotating magnetic field generated by the stator forms a loop with the rotor permanent magnet poles and the rotor core. According to the principle of minimum reluctance, that is, the magnetic flux is always closed along the path with the minimum reluctance, and the electromagnetic force of the rotating magnetic field is used to pull the rotor to rotate, so the permanent magnet rotor will follow the rotating magnetic field generated by the stator to rotate synchronously, thereby driving the motor shaft to rotate.

2.2.2 Power generation principle of permanent magnet synchronous motor

According to Faraday's law of electromagnetic induction, part of the conductor of the closed circuit is provided by the three-phase stator winding, and the magnetic field is provided by the permanent magnet on the rotor. When the external torque drives the rotor to rotate, a rotating magnetic field is generated, cutting part of the three-phase stator winding Conductors generate induced three-phase symmetrical current. At this time, the kinetic energy of the rotor is converted into electrical energy, and the permanent magnet synchronous motor works as a generator.

Advantages and disadvantages and application range of 2.3 permanent magnet synchronous motor

The advantages of permanent magnet synchronous motors are small size, light weight, and high power density. Compared with asynchronous motors, they have low energy consumption, low temperature rise and high efficiency. It can be designed as a structural motor with high starting torque and high overload capacity according to demand. The permanent magnet synchronous motor is strictly synchronized and has good dynamic response performance. It is suitable for frequency conversion control. The torque and speed of the motor can be adjusted in a wide range by adjusting the current and frequency. However, the permanent magnet material in the permanent magnet synchronous motor is usually made of neodymium iron boron strong magnetic material, which is relatively brittle and hard, and may be broken by strong vibration; and the rotor is made of permanent magnet material, which will occur when the motor is used and over-temperature. Magnetic decay occurs, resulting in a drop in power. At present, permanent magnet synchronous motors are widely used in new energy vehicle motors. The new energy markets in Asia and Europe mainly use permanent magnet synchronous motors as new energy motors.