How electric car motors work

Neelesh Vasistha Jun 25, 2021 · 3 min read

We’ve spoken at length about car batteries: how they work, their materials and recyclability. But while batteries steal much of the discussion around EVs, they just store energy, not turn wheels. This article prises the lid on what literally drives electric cars: the motor.

Engine vs motor

First, a quick semantic check. While ‘engine’ and ‘motor’ are used interchangeably — (across languages too; der Motor is the German word for engine) — they’re technically different. Engines convert heat, like combustion, to movement. BEVs don’t use combustion and thus have motors, not engines. This might sound trivial — but can you imagine a ‘jet motor’, instead of jet engine, or ‘engine generator’, instead of motor generator?

Parts of a motor

An electric motor contains only a skeleton crew of parts. The torque that turns a car’s wheels originates in the rotor; a spinning shaft attached to a stator, which remains static. Bearings help the rotor spin on its axis, and windings provide a path for electric current to flow. The commutator ensures that this current flows in the right direction through the windings.

Finally, with so few parts, the space between them also becomes operative. The air gap refers to the distance between stator and rotor. It needs to be large enough to prevent them touching, while staying small enough to remain efficient

How electric motors work

Electric motors can be synchronous or asynchronous, each offering their own benefits. Both operate using magnets. Most of us have a high school understanding of how magnets can repel or attract. It’s this force of physics that, on a mechanical scale, ultimately drives an EV.

The asynchronous, or induction motor, was invented by Nikola Tesla. Here, the battery supplies electrical energy to the stator, whose coils are arranged to create a rotating magnetic field. This excites the rotor into an endless chase, which spins the gears of the cars, and in turn, the wheels. The industry considers induction motors cost-effective and reliable. They’re apt for EVs that drive fast for long periods.

In a synchronous motor, the rotor itself is an electromagnet. And because it helps create the magnetic field, it rotates at a speed relative to the current. Such a system is ideal for urban driving, which involves regular stopping and starting.

Traditional cars also have batteries, recharged by an alternator. But EVs are unique in this sense—despite using regenerative technology, there is no separate alternator; the motor covers this too. When decelerating, the motor reverses the principle employed to generate torque. Using electromagnetic resistance, it captures the kinetic energy of the rolling car, translates it back to electricity, and sweeps it into the battery.

How is this different from ICE?

Electric motors also present some ownership benefits. If you’ve had a traditional car, you’ll know the regular and often painful maintenance needed. An ICE houses a lot of moving, mechanical parts. These are sensitive to wear and tear, meaning an unserviced car will break down sooner or later. Compared to the 2000 moving parts in an ICE, an electric motor has 20. So there’s simply less to go wrong—and when it does, it’s easier to identify and replace. This reflects in maintenance schedules. Depending on manufacturer, most EVs are sent for servicing every couple of years, compared to once a year for ICE cars. This leads to heavy savings for EV drivers, especially as cars age.

Driving forward

Electric motors are the rhythm guitarist of an EV —cool, understated, and smirking with a quiet confidence. Flashier technologies like batteries and connectors may soak up attention, but a car would sit dead in the parking bay without its motor. And while EVs provide benefits for cities and planet, drivers can thank the elegance of their electric motor for saving them tangible money over time.