Induction vs Permanent Magnet Synchronous Motor

Modern electric vehicles mostly use Permanent Magnet Synchronous Motor (PMSM) and Induction Motor to operate.

This article dives deep into the details of the pros and cons of Induction Motor vs Permanent Magnet Synchronous Motor. Among the top carmakers, only Tesla primarily uses Induction Motors in its EVs. Almost all other EV makers equip their electric cars with PMSM. There are distinct advantages and disadvantages of using either of these. Before studying that, it is also critical to understand the fundamental working principle of these.

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Induction Motor vs Permanent Magnet Synchronous Motor – Working Principle

Induction Motor

Tesla uses AC Induction Motor in Model S but uses PMSM in Model 3. It is one of the few automakers which uses both. In the case of Induction Motors, there is a stator and a rotor. The stator consists of motor windings which induce an opposing magnetic field in the motor. As a result, rotational torque is generated which rotates the rotor.

Since there is always a slip between the rotor and stator, these motors operate with an average efficiency of around 90-91%. In other words, there is always a lag between the applied stator current and the resulting rotor opposing field. That is also the reason why these are called Asynchronous Motors.

Permanent Magnet Synchronous Motor

On the other hand, most carmakers use PMSM in their EVs. As the name indicates, these motors use permanent magnets to generate a field, allowing the rotor to rotate. It also has a stator, just like the Induction Motor. The materials used for the permanent magnet can vary from expensive Iron Neodymium Boron to sintered powder metal.

The main principle of PMSM is that it runs synchronously with the applied frequency. In essence, there is no lag between the applied and induced field. That is why these cars have efficiencies of upto around 97-98%. While the difference in efficiencies might not seem all that much, but over a long period of operation, a lot of energy, and in turn money, can be saved using PMSM.

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Induction Motor vs Permanent Magnet Synchronous Motor – Pros and Cons

Induction Motor

These can be used without VFD (Variable Frequency Drive).
These are relatively cheaper.
These have a simple and rugged construction.
These require minimal maintenance.

Permanent Magnet Synchronous Motor

These have high energy density.
These have higher efficiency.
These are compact in dimensions.
These weigh less.
These generate constant torque.

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Learn Electric Cars Says

Both these types of motors find the maximum application in modern EVs, PMSM more so than Induction Motors. Still, there are other electric motors available even though these are not as widely used. We would like to mention a few of these: