2017 Tesla Model 3 Has Unexpected Electric Motor Design

Among all the normal stuff you were reading last week, here's something you might have missed: the little slice of the internet devoted to Tesla forums went crazy. Someone uncovered the 2017 Tesla Model 3's certification papers on a public corner of the Environmental Protection Agency website. And there's good reason these papers caused a stir: the filing documents revealed things that Tesla wouldn't talk about during the car's initial debut handover event in July.

The papers show that the long-range Model 3's rated battery capacity is 80.5 kilowatt-hours (the actual usable capacity that Tesla historically uses to badge its models, which is always lower, never appears on such documents). They also state that its electric motor produces 258 horsepower. But these facts were arguably not the most important bits of information contained within the EPA documents.

The big news is this: the Model 3 uses a permanent magnet (PM) electric motor instead of the AC induction motors used in all Tesla products to date.

It may sound like a nerdy difference, but this is a huge deal on many levels. Tesla's entire identity is tied up with the AC induction motor, a type that Nikola Tesla himself patented in the late 1880s. Not only that, the Tesla logo is said to be a cross-section of one lobe of one of its own AC induction motors. Tesla is the only production electric carmaker with this type of motor, so it has historically bad-mouthed the PM motors used by everyone else. Tesla liked pointing out that PM motors tend to be less efficient when operated at higher speeds. Also, such motors are made from rare earth elements, which are mostly mined in China and are thus subject to trade politics. No wonder Tesla didn't feel like revealing this nugget at the Model 3's coming-out party, which was well-attended by Tesla fans who are invested in the Tesla story.

But none of this is bad news for consumers or deposit-holders waiting in line to buy a Model 3. In fact, it's a good thing. For one, PM motors are more efficient, so long as you're not intent on building a hyperperformance machine. This makes them a better choice for daily-driven commuter vehicles. Not to oversimplify it too much, but AC induction motors have to use some of the electricity stored in the car's battery to generate the necessary magnetism within the motor. Permanent magnet motors have no need for this because they are made using, as the name suggests, permanently magnetic materials.

This change has many cascading benefits, especially if you are trying to build a smaller, less-expensive electric car. A more efficient electric motor means you can use a smaller battery to achieve a given range, which not only lowers the price, but also reduces the battery's weight and footprint. A smaller and lighter battery in turn allows for a smaller and lighter car, which increases efficiency and range and reduces the need for a big motor even more. It's a self-reinforcing change that makes the Model 3 possible, as well as affordable.

And there are other important details that went unnoticed by those who first uncovered the EPA documents: Namely, a summary of the test results that will underpin the official range and "fuel economy" ratings that will eventually appear on the Model 3's window sticker.

From these we can see that the Model 3 will be the first Tesla that's rated higher in the city than it is on the highway. That's not because freeway efficiency is substandard (that, too, is better than any other Tesla) but because around-town efficiency is vastly improved. Our analysis of the raw numbers suggests it's entirely possible we'll see Model 3 efficiency ratings that exceed those of the Chevrolet Bolt, which is good for 119 miles per gallon equivalent and 28 kWh per 100 miles in a mix of city and highway driving. For comparison, the thriftiest Tesla Model sold to date is the Model S 60D, which is rated at 104 mpge and a somewhat unimpressive 32 kWh per 100 miles. Furthermore, we would not be surprised if Elon Musk announces that the long-range Model 3's range will climb above the 310-mile preliminary estimate Tesla shared at the handoff party by as much as 20 miles, possibly more.

The final bit of interesting information comes from what the 2017 EPA filing documents don't say. There's no mention of a 2017 standard-range Model 3. That seems to clinch the idea that we won't see any of those vehicles until 2018. And with no filing from Tesla on the base car, there's no range and consumption data we can analyze. Not yet, anyway.

All of this bodes well for the range and efficiency of the Model 3. The numbers that Tesla shared at the handover event look that much more believable, now that we know more about the motor, the battery and the raw numbers the company has submitted to the EPA.