Tesla made a significant change to its electric motor strategy with the introduction of the Model 3, switching from an AC induction motor to a permanent magnet motor.
Now, Tesla’s principal motor designer, Konstantinos Laskaris, explains the logic behind the move.
We recently reported on Laskaris because he went to school at the National Technical University of Athens in Greece, like several other top motor designers at Tesla. The automaker recently confirmed that they are building an electric motor R&D group in Greece to tap into strong local electrical engineering talent.
At the Coil Winding, Insulation & Electrical Manufacturing Exhibition (CWIEME) in Chicago, Laskaris made a rare comment about Tesla’s decision to use a permanent magnet motor in the Model 3 instead ofan AC induction motor, like in Model S and Model X.
He said (via Charged):
“It’s well known that permanent magnet machines have the benefit of pre-excitation from the magnets, and therefore you have some efficiency benefit for that. Induction machines have perfect flux regulation and therefore you can optimize your efficiency. Both make sense for variable-speed drive single-gear transmission as the drive units of the cars.
So, as you know, our Model 3 has a permanent magnet machine now. This is because for the specification of the performance and efficiency, the permanent magnet machine better solved our cost minimization function, and it was optimal for the range and performance target.
Quantitatively, the difference is what drives the future of the machine, and it’s a tradeoff between motor cost, range and battery cost that is determining which technology will be used in the future.”
It sounds like the decision was driven by efficiency and costs. Tesla is still far from reaching its cost target for the Model 3, but they can say ‘mission accomplished’ for efficiency since the Model 3 is one of the most efficient vehicles on the market, according to the EPA.
One of the main concerns with permanent magnet motors is that they often use rare-earth materials, which are controversial because of health risks and geopolitical issues. But not much is known about the design of the Model 3 motor at the moment.
A recent look at the motor (linked below) suggests that Tesla refers to it as ‘PMSRM’, which could mean ‘Permanent Magnet Switched Reluctance Motor’, a new type of motor with thin permanent magnets, but it’s unclear at this point: