MitchJi
10 MW
I’d love to get a better understanding of the implications of this motor. Elon said that it is switched reluctance motor. There are some controversy over that statement. How important is this?
https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/
https://cleantechnica.com/2018/03/11/tesla-model-3-motor-in-depth/
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You would examine all the different electric motor architectures that exist. In doing so, you would come across a design that’s actually older than Nikola Tesla’s 1892 invention. More than 50 years earlier, the reluctance machine had been invented in 1838. And it’s a surprisingly sweet design. The reluctance machine is simple, it’s efficient, it’s compact in size. And, it’s inexpensive to produce. Yet the reluctance motor sat on the shelf for over a century, suffering from a debilitating disease called Torque Ripple (due to the reluctance machine’s propensity to incur a phenomena know as cogging). Torque ripple simply means that the power output of the reluctance motor fluctuates up and down. Certainly not good for an EV. When you put the pedal to the metal, you want a nice smooth acceleration ramp.
The reluctance machine was partially rescued by the same technology that made it possible to put the induction motor into an electric car — power electronics from Silicon Valley. The reluctance motor is notoriously difficult to control (RPM, determination of rotor position, etc.), but modern inverters and control systems helped overcome that foible. Still, the torque ripple issue remained a challenge even as the 21st century approached. But in poking around, you start to notice some research on the topic taking place in the first decade of this century. You come across a 2011 research paper claiming that the torque ripple issue has been addressed. The researcher had embedded some small rare-earth magnets in the stator of a reluctance motor right along with the existing electromagnets. In doing so, the torque curve had smoothed out. As a bonus, the paper claimed to achieve a 30% boost in power output with the inclusion of the rare-earths. Now there’s some first principles thinking. Whoever first thought of lacing the stator with rare-earths has apparently come up with the greatest marriage since someone thought to sink a chocolate bar into a jar of peanut butter, producing the Reese’s Peanut Butter Cup.
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