Published by Emily Ruck Keene on 02.23.2021 - 4 min
Even if you’re familiar with the inner workings of a diesel- or gasoline-powered vehicle, this doesn’t mean you also know exactly what happens inside the motor of an electric car. Read on for all the important information when it comes to electric car motors, but with as little jargon as possible.
How does an electric car motor work? In an electric vehicle, when the driver applies the accelerator, the battery in the car supplies electricity to the stator, causing the rotor to turn, and subsequently provide mechanical energy to turn the car’s gears. Once the gears are rotating, the wheels turn too. All this happens in the blink of an eye, and without fossil fuel combustion!
What are the types of electric car motors and how do they run?
Alternating current (AC) and direct current (DC) are two different types of electric flow. As their names would suggest, direct current is when the electric charge flows in only one direction, while alternating current periodically reverses direction.
Motors powered by direct current can be found in an electric vehicle, but only as small, mini motors used, for the windshield wipers and electric windows, for example, but not to drive the vehicle itself. For the traction of an electric vehicle, an alternative current motor is used.
There are two types of AC electric motor used to create traction for an electric vehicle: asynchronous (aka induction) and synchronous.
In an asynchronous, or induction, motor, the rotor is pulled into a spin, constantly trying to “catch up” with the rotating magnetic field created by the stator. This type of electric car motor is known for its high power output and is a common motor in vehicles.
In a synchronous motor, on the other hand, the rotor turns at the same speed as the magnetic field. This provides high torque at low speed, making it ideal for urban driving. Another advantage is its size: a synchronous electric car motor can be compact and low weight.
Before your asynchronous or synchronous electric car motor can turn, the electricity it needs has to go through several steps before it reaches its final destination as traction.
Don’t get confused between the alternating current electric car motor and the types of electric ; which can use either alternating or direct current depending on whether you are plugging directly into the grid, or using a specific type of charging station. While your electric car motor uses AC, the battery needs to receive its electricity in DC. A conversion from alternative to direct current, either onboard or outside the vehicle, is therefore required.
Power from the grid is always AC. This then passes through your electric vehicle’s onboard charger (imagine it as an AC to DC converter), which then sends the power to the battery. But the rapid charging stations you can find on the highway, parking lots and on city streets carry out the AC to DC conversion process themselves, meaning the energy for the battery arrives straight into the car as direct current. They are faster than AC electricity outlets, but take up much more space.
How does the car then turn DC into AC for its motor? Using an inverter, a device in the powertrain…
In an electric car, the electric motor is just one part of a larger unit called the powertrain. Here we also find the Power Electronic Controller (PEC), in charge of the electronics that control the motor’s power supply and battery charging, and the gear motor which adjusts the torque (turning force) and speed of rotation.
Constructing the different elements of an EV motor requires real expertise. At Renault, supervisor Tatiana Sueur explains that “To build a stator, for example, we had to find how to wind 2 kilometers of copper wire into little notches in sheet metal without damaging the insulating ceramic that covers them.”
Powertrain efficiency is constantly being improved, as we have seen at Renault with the technical innovations within ZOE’s powertrain unit, which leads to better all-round vehicle performance and the introduction of more features.
The life expectancy of an electric car motor depends on so many variables that it is difficult to estimate. In ideal conditions, it has been suggested that the optimal lifespan is between 15-20 years. Compared to a combustion engine, an electric car motor has fewer parts, meaning reduced and easier maintenance.
When it comes to an electric vehicle, power output involves the difference between the electricity delivered (input) and the “useful” mechanical energy that drives the motor (output), a ratio known as energy conversion efficiency. Heat and friction can cause some of this power to be lost along the way, meaning the motor doesn’t benefit from all of the electricity coming from the battery of the electric car.
The power output of an electric car depends on the volume of its motor and the wattage of the incoming current. ZOE, for example, generates an output of 100 kW with an improved torque of 245 Nm. With a WLTP* range of 395 kilometers thanks to a 52 kWh battery, New ZOE performs especially well when it comes to energy efficiency.
A hybrid electric vehicle uses both an internal combustion engine and an AC motor powered by a battery. Traditionally, batteries on hybrid vehicles could only be recharged through regenerative braking or slowing, meaning that most of the work was carried out by the combustion engine.
Today, however, a new breed of hybrid model is available: the Plug-in Hybrid Electric. These vehicles, such as the Renault Captur E-TECH Plug-in, are equipped with a dedicated charging socket, two electric motors and a combustion-powered engine for the best of both worlds.
*WLTP: Worldwide Harmonised Light Vehicle Test Procedure. The standard WLTP cycle corresponds to 57% of city journeys, 25% of suburban journeys and 18% of motorway journeys.
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