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Speaking of motors, we must first let everyone know what an induction motor is and what a permanent magnet motor is.

Let me take a look at popular science. Many of my friends may not know the specific principles of the two.

An Induction Motor is what we call an AC asynchronous motor. Its excitation, that is, the generation of a magnetic field, relies on current . That is to say, part of the current is used to generate a magnetic field. Why this magnetic field can be generated can refer to how the generator generates electricity. These two processes are exactly the opposite. Then the speed of the rotor is not synchronized with the speed of the rotating magnetic field, so it is called an asynchronous motor. It is because of the asynchronous, so it produces slip. The slip causes the conductors on the rotor to generate current and rotate in the magnetic field. It is also because of this asynchronous, it is a little more complicated to control than synchronous. Induction motors are coils and rotor cores, so they are cheap, low cost, strong overload capacity, strong performance, and durable.

Permanent magnet motors mainly refer to permanent magnet synchronous motors, and permanent magnet refers to the use of permanent magnets for excitation, that is, magnets. The performance of magnets was not good before, but the stable performance and wide application of the “magnet king” Ru FeB make the reliability and stability of permanent magnets better and better, and the phenomenon of demagnetization also occurs less frequently. Synchronization means that the speed of the rotating magnetic field is consistent with the speed of the rotor. To control the speed of the rotor, you only need to control the speed of the magnetic field, that is, the frequency of the alternating current. Synchronization is naturally more convenient to control.

Knowing this principle, it is actually very easy to analyze the performance.

First of all, the permanent magnet motor does not have the current component of the excitation, and the efficiency is higher, especially in the high-speed area, the same battery pack can bring longer battery life. The cost of a permanent magnet synchronous motor is higher than that of an induction motor, but this cost is negligible compared to the cost of the battery.

Secondly, the induction motor has strong overload capability and more robust performance, so the acceleration capability is stronger than that of the permanent magnet synchronous motor.

Thirdly, the induction motor has a wide speed adjustment range, but the control is slightly troublesome. Although the permanent magnet synchronous motor has a narrow speed adjustment range, the control system is simple.

Thirdly, the induction motor is durable, and the permanent magnet synchronous motor may demagnetize under high temperature and strong vibration.

Finally, NdFeB materials were not available in the United States before, and they were all imported. It is estimated that Musk is very worried, afraid that it will get his neck when it is used. Now it seems okay. Tesla will also build a factory in China, so use permanent magnets.

Therefore, these two motors have their own characteristics in terms of performance, and there is no strict distinction between good and bad. Tesla can use which motor, but it is a comprehensive consideration of performance, cost, supply chain and many other factors. It happens to be on model 3. I chose a permanent magnet synchronous machine.

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