GM Reveals Details Of Its Ultium Electric Motors

In the old days of cars, cubic inches were the first thing on everyone’s mind. In the new world of electric cars, efficiency is the key parameter. More efficient cars go further on a single charge and may need smaller (and less expensive) batteries to meet the needs of the […]

In the old days of cars, cubic inches were the first thing on everyone’s mind. In the new world of electric cars, efficiency is the key parameter. More efficient cars go further on a single charge and may need smaller (and less expensive) batteries to meet the needs of the motoring public.

We have heard a lot about the Ultium batteries GM is manufacturing with its partner, LG Energy Solution, at a new factory in Lordstown, Ohio. In fact, the two companies have agreed to build a second battery factory near the Spring Hill, Tennessee, facility where the Cadillac Lyriq will be produced.

Ultium Is More Than Batteries

Ultium is actually GM’s name for its entire electric vehicle platform that will be the basis for all of its electric cars going forward. Like the MEB platform Volkswagen is using for most of its new electric car offerings, the Ultium chassis can be lengthened or shortened to fit a variety of vehicles. It can be make wider or narrower, as the needs of the company require. It can add more battery modules or use fewer of them.

In a recent interview with Green Car Reports, Tim Grewe, GM’s head of global electrification strategy, talked about the electric motors and software controls that will be part of the Ultium platform.

The company has designed three electric motors in-house — a 180 kW (240 hp) permanent magnet motor for front-wheel-drive applications, a 255 kW (315 hp) permanent magnet motor that can be used in front or in back, and a 62 kW (83 hp) all-wheel-drive assist induction motor that can be used in front or in back. (I suggested doing something like this to Saturn back in 1996. They laughed at me. Fools!)

The motors will be packaged with an inverter and gearset in various combinations to go into a generation of fully electric vehicles ranging from the GMC Hummer to family sized crossovers like the Chevrolet Equinox. They may be used in the next-generation Chevy Bolt or in high-performance cars like the Chevy Camaro. EVs from every GM brand — Buick, Cadillac, Chevrolet, and GMC — will utilize the components as well as future Honda and Acura models. The ability to manufacture them from a few basic components will help achieve economies of scale that will translate into lower prices for the vehicles they are installed in.

Hummer Ultium platform. Credit: GM

The Hummer EV, for instance, uses three of the 255 kW motors — two in back and one in front — for a total of 945 horsepower. Grewe also hinted at a future mainstream Chevy crossover that will have the 180 kW motor in front, together with an on-demand 62 kW traction motor in back. Given the 5 possible motor layouts and the flexibility of the Ultium battery pack, GM says it has as many as 19 different battery and drive unit combinations on the shelf and ready to go into its electric cars of the future.

Customization & Commonality

Even though the new motors include both permanent magnet and induction designs, they were designed to be built as a scalable family that uses similar tooling and manufacturing. They share a common stator and are designed to use common winding tools, common magnets, and common hairpins.

It’s similar to how batteries are combined in parallel or series with combinations of hairpins and conductors plus a turn count tweaked to match the voltage, Grewe said. The motors will be cooled by a type of transmission fluid that has been specially designed to prevent foaming. GM won’t actually manufacture the motors itself but will use an as yet unidentified production partner.

GM has also developed its own software in-house to control these systems with what Grewe calls “some novel techniques.” One of those techniques is overmodulation of the systems, with the power level potentially updated every 10 microseconds, which Green Car Reports calls a smart tradeoff between switching loss and conduction loss.

It allows the software to fine tune the behavior of the motors for very low load conditions that might be a drain on efficiency for other units and to expand the sweet spot in which the motors can achieve their maximum efficiency of around 97 percent. Grewe adds that it’s also the key to natural-feeling one-pedal driving.

Crate Motor Option

Ultium 255 kW motor. Credit: GM

The Chevy small block V-8 engine first appeared in 1955. Since then, it has powered a dizzying variety of cars, boats, off-road vehicles, and backyard specials. Grewe suggests GM’s new suite of electric motors could become the electric crate motors for a new generation of performance enthusiasts. “Some of the creativity that you have with those crate engines and great motors that comes out of this is just going to be natural in the industry,” he says.

Ultium may be a silly name made up of GM’s marketing gurus, but the actual motors are proof that The General is taking the EV revolution seriously.


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Shaqil Heaton

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