A Tour of your EV “Engine” | VinFast

[VF Staff 7]

A Tour of Your EV “Engine”

A few articles back, we gave readers a tour of their gas-powered combustion engine. But, combustion engines are (hopefully) soon to be a product of a bygone age. Out with fossil fuels—and in with electric vehicles (EVs).

As such, we thought it would be appropriate to give you a second tour. This time, of an EV “engine” (and, yes, there’s a reason for the quotation marks). Before we start, we’d like to make a disclaimer: This article is specifically about all-EVs. This isn’t an article about the engines of plug-in hybrids.

So, with that stated… let’s get started.

Electric Car “Engines”

First things first: astute readers may already know that all-EVs don’t have “engines.” Rather, they’re powered by electric “motors.” Motors have fewer moving parts, but due to their lack of distinguishable physical features, can be difficult to grasp. Gas engines essentially run on miniature explosions: we understand, intuitively, where the power turning our wheels comes from. That’s less true of electric motors.

Likewise, there are several kinds of electric motors. We’ll give a brief overview of the two most common ones, but we’ll stick to focusing on general trends within EVs.

Luckily for you (and for me, as a writer), the ins and outs of an electric motor are, overall, easier to explain than that of a gas engine. We’ll start with the charger, then follow the electric and kinetic energies through to their end-points, in hopes of giving you a better understanding of how your EV works.

The Charger

As mentioned, our journey begins with the charging port. It may look like a simple device: plug the cord from the charging box into your car and wait. Right?

Wrong. See, electricity comes in two types: alternating current (AC) and direct current (DC). Yes, like the band. They are exactly as described: alternating current constantly changes direction and voltage (from positive to negative), while direct current goes in one direction and remains stable. Most EV batteries hold DC energy… but the grid is powered by AC.

So, before the electricity goes anywhere, it must pass through the onboard charger, which converts it from AC to DC. It does more, too: it monitors battery status (including current, temperature, charge, and voltage), and communicates with charging equipment. In fact, if you hook up to a “DC Rapid Charger” (sometimes called a “Level 3 Charger”) this is all it does, as the need to convert between AC and DC is rendered moot.

The Traction Battery Pack: The Big Boy

From there, the electricity—now in the form of DC—flows to the biggest, most expensive part of any EV: the Traction Battery Pack. This isn’t your average car battery. It may be as big as the entire underside of your vehicle. The traction battery pack holds electricity that will be used by the electric traction motor that makes the car run. But it also is the first stop for electricity heading elsewhere. Now, we must go in two different directions: first, towards auxiliary systems, then towards the motor itself.

The DC/DC Converter: Not as Redundant as It Sounds

The DC power used by the traction battery pack is high-voltage. High enough that it may well fry simple devices like your speakers and lights. As such, the power used to supply auxiliary systems like your stereo is transferred from the traction battery pack to the DC/DC Converter, where it’s converted to lower-voltage DC energy that won’t fry other systems.

The Auxiliary Battery

In many EVs, the DC/DC Converter then sends the newly-low-voltage DC energy to an auxiliary battery reminiscent of the one you’d find in a gasoline vehicle. As such, it’s simple to understand: it powers things other than the motor. Lights, stereo, your horn, you name it. If it needs power but doesn’t make the car move, it’s probably powered by the auxiliary battery.

Now, back to the motor…

Backing Up: The Power Electronics Controller

Electricity from the traction battery goes to two places. We’ve already explored the first. Here, we’re going to explore path two, which leads to the motor.

The first stop is the Power Electronics Controller. This device manages the amount of electricity sent from the traction battery to the motor and is usually controlled by your acceleration pedal. Press harder, and it sends more power to the electric motor to increase speed and torque. Simple, right?

Well, not always. Not all motors use the same kind of electricity. Some use AC, some use DC. As such, this is also where there might be another converter that changes the DC power used by the battery to the AC power the motor might need.

The Electric Traction Motor: Magnets are Magic

While much of the machinery behind an EV may be simple, the electric traction motor isn’t, and it doesn’t help that there are multiple motors in use, depending upon the manufacturer. So, we’re going to start with the core concept, then go from there. We’re going to try and eschew deep science (those who know all the terminology: I apologize in advance), so you’ll understand the core mechanisms that underlie it.

Magnets are Magic

At the core of every electric motor is magnetism. Specifically, magnets that are being turned off and on again, in rotation. While the details are much more complicated, it works like this:

On the outside is a “stator:. It’s like a big, hollow, metal tube. Placed in the middle of the stator is a rotor. The rotor needs to move to provide the kinetic energy that makes the wheels spin. So, how do you do this with electricity?

You arrange magnets and loops of copper windings of various kinds to create an array of magnetic devices that can be turned on and off, have their polarity suddenly reversed, or use an alternating current that sort of “flows” through the windings, causing the same effect. Then, what you do is set them to turn on and off in rotation or flip polarity. This creates a “rotating magnetic field,” which is exactly what it sounds like.

Think of it like this: you drive a stake into the ground and tie a rope to it, with a metal ball at the end of the rope. Then you take a strong magnet and spin it around the stake just outside the metal ball’s range. The smaller magnet will be pulled along by the stronger one, spinning faster and faster around the stake.

The rotor does the same thing: the rotating magnetic field causes it to spin, and that spin provides the underlying kinetic force that, eventually, turns the wheels.

The Different Kinds of Motors

There are several different kinds of electric motors, some of which have been in use since the 1900s. MotorTrend does a great analysis of them, which you should read. But, not all are regularly used in EVs. We’ll avoid discussing those that are only used in a minority of vehicles, and try to avoid the more technical terms where we can.

The first and most common is the “Permanent Magnet Motor.” In these, magnets are attached to the rotor and always “on,” but send the “alternating current” we described before to the stator. These are often called “synchronous” motors, as the fact that the magnets are always active means they follow along at the speed of the current.

There is a big problem with these motors, though: the magnets require rare earth materials that are increasingly difficult and environmentally devastating to find.

The second most common is also the most difficult to understand. It’s called “AC Induction.” In this, we remove the rare earth magnets, while maintaining the alternating current running through the stator. That current produces a magnetic field that interacts with materials in the rotor, creating another magnetic force that pushes the rotor along.

Motor Feedback

The motor is rarely just a one-way device. Rather, the rotation of the wheels can move the rotor, creating a magnetic field going in the other direction and powering the battery. This creates drag, too, which slows the vehicle’s movement.

Transmission, Wheels, and Cooling: End of the Line

From there, the rotating force of the rotor reaches the transmission, which—through an arrangement of cogs and gears not dissimilar to what you’d find in traditional engines—transfers that kinetic rotation down to the wheels, moving your vehicle forward.

But, all of this is a very heat-intensive process. As such, a substantial cooling system is usually attached to these various electronics to vent heat and keep the vehicle in working order.

The Devil is in the Details

That’s a rundown of how EVs work! But, there is something else to consider: this is a heavily simplified article aimed at those new to electric “engines.” Likewise, EVs are an incredibly innovative space full of all sorts of changes. As such, there’s bound to be a huge variety of engine types, motors, and other details we couldn’t cover here without losing the focus of this article. It could even become outdated in short order, and we likely sacrificed some detail accuracy in the interest of making it easy to understand.

If it’s a topic that interests you, we recommend using this article as a springboard. Feel free to follow any of the links to our sources above, which dive into different parts of the process in more detail, and see what you learn.

Until then, we hope you’ve enjoyed the read!

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[Martin Cochet]

Thanks for all the explanations, are the VF motors “permanent magnet” or “AC induction” type? And do they need less maintenance than ICE engines?

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[VF Staff 7]

Hello Martin, thank you for being a Community Member! VinFast vehicles have Permanent Magnet electric motors. Electric motors have fewer moving parts compared to ICE engines which results in less maintenance over the lifetime of the vehicle

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