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Mechanism and principle of rare earth permanent magnet motor
- Dec 06, 2018 -

Mechanism and principle of rare earth permanent magnet motor

The rare earth permanent magnet synchronous motor is mainly composed of a rotor, an end cover, and a stator.

In general, the stator structure of a permanent magnet synchronous motor is very similar to that of a conventional induction motor, and the unique structure different from the rotor is different from other motors.

The biggest difference from the AC induction asynchronous motor used by Tesla is the high quality permanent magnet pole (rare earth) placed on the rotor.

Since there are many options for placing permanent magnets on the rotor, permanent magnet synchronous motors are usually divided into three categories: in-line, surface-mount, and plug-in.

And their working principle is about the same. Three-phase current is applied to the stator winding of the fixed motor. After the current is applied, a rotating magnetic field is formed in the stator winding of the motor. Since the permanent magnet is mounted on the rotor, the magnetic pole of the permanent magnet It is fixed. According to the principle that the magnetic pole's isotropic absorption is repelled, the rotating magnetic field generated in the stator will drive the rotor to rotate.

Technical bottleneck of rare earth permanent magnet motor

1, control problems

A permanent magnet motor can maintain its magnetic field without external energy, but it also makes it difficult to adjust and control its magnetic field from the outside. It is difficult for a permanent magnet generator to adjust its output voltage and power factor from the outside. The permanent magnet DC motor can no longer adjust its speed by changing the excitation.

2, the cost problem

Since rare earth permanent magnets are currently relatively expensive, the cost of rare earth permanent magnet motors is generally higher than that of electric excitation motors, which needs to be compensated for by its high performance and operating cost savings. Therefore, the permanent magnet motor is suitable for applications with low power.

3, demagnetization problem

Rare earth permanent magnet motors are more demanding in the working environment. Rare earth permanent magnet materials exceeding 180 °C will have irreversible demagnetization and failure conditions; they will be easily broken under severe vibration or temperature difference; materials are easily oxidized and corroded, and surfaces must be surfaced. The coating can be used; the rare earth permanent magnet motor is very sensitive to overload, and once it is overloaded, it will cause demagnetization of the permanent magnet material.

At the same time, the electromagnetic load of the rare earth permanent magnet motor is very high, and the magnetic field is difficult to adjust after the manufacture, and the power control system is much more complicated than the induction motor. Traditional motor design theory, calculation methods, and motor control systems cannot meet the development requirements of high-performance motors.

All in all, on the road to the development of rare earth permanent magnet motors, there are many difficulties. But how to see the rainbow without going through the storm, and in the face of air disasters, the tireless efforts of the car engineers will eventually break through the bottleneck, and the public can also benefit from the convenience brought by technology.

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