The Science of the Electric Motor

Motors are at the heart of any electric vehicle. They are also, as you might expect given their name, the source of much confusion among new EV drivers. What exactly is an electric motor? How do they work? And why do they put out so much torque? A motor is a mechanical device that converts one type of energy into another. In the case of an EV motor, that conversion takes place through spinning magnetic fields. Understanding how those fields spin in an electric car motor will help you better understand why your EV has such impressive acceleration and why regenerative braking helps you get more range from every charge.

How Electric Motors Work

Most of us are familiar with the workings of a gas-powered car engine, but how exactly does an electric motor work? Surprisingly, it’s less complicated than the combustion engine. First, you have to understand how current flows. Electricity travels through conductors like wires by moving electrons. Electrons can either flow freely or be bound to atoms by some form of electromagnetism. When the electrons move freely, we call this Direct Current (DC). This can be converted to the Alternating Current (AC) that we use for power transmission and distribution. In an electric motor, AC is converted to DC, sent through the motor’s spinning electromagnetism, and then converted back to AC as it leaves the motor as a form of propulsion. The electromagnets in an electric motor are made up of a series of coils of wire around a core of ferromagnetic material. When you energize these coils with DC, a force is created between the north and the south poles of the core, causing the core to turn. The more current you put through the coils and the more wraps of wire you have around the core, the stronger the force between the poles and the greater the torque of the motor.

Understanding Torque in an Electric Motor

Torque is the rotational force that causes a motor to turn. It’s also a measure of how hard a motor has to work for a specific load. The higher the torque, the more work the motor has to do and the more power it consumes. In an efficient combustion engine, the combustion of fuel and air creates torque, which turns the crankshaft. In an EV motor, the current running through the electromagnetism produces the force that causes the core to turn, generating torque. That motor torque is the main thing that differentiates electric motors from engines. The amount of torque your motor can generate is related to its size, the strength of its electromagnets, and the amount of current running through it. The higher the torque, the faster your car can accelerate and the more torque it can handle while driving up a steep hill.

Regenerative Braking and Efficiency

The use of regenerative braking is the most important feature of electric vehicles. It enables the car to feed the energy normally lost in the braking process back into the battery. It’s like charging your car while driving. For a conventional car, the energy lost in the braking process is wasted. The energy that was used to drive the wheels is turned into heat by the friction of the brakes. Because an EV has two sources of current that can be converted into electricity, it can capture the energy from both braking and driving and use it to charge the battery. So when you press the pedal, the current from the battery flows to one set of electromagnets. When you press the brakes, the current from the battery flows to electromagnets that are connected to the other set of magnets. The resulting electromagnetic force creates the torque needed to slow the car and the car’s kinetic energy is converted into electricity that charges the battery.

How Electric Motors Produce Instantaneous torque

The current in an electric motor creates a magnetic field that constantly changes in strength. The core of electromagnetism is constantly trying to align itself with the field of the core. When it does, it spins in one direction. When it can’t align, it stops spinning. The more current you have running through the electromagnets, the stronger the electromagnetic field and the more frequently the core is stopped and started spinning. It’s this stopping and starting of the core that causes the instantaneous torque of an electric motor. If a core was able to spin at a constant rate, it would produce power at a constant rate. But the core in an electric motor is constantly slowing and speeding up. This generates sudden bursts of power as it accelerates and decelerates. The more current running through the electromagnets, the more frequently the core stops and starts spinning, producing more torque.

Final thoughts

In summary, the Science of the Electric Motor comes down to this; A DC is converted to AC as it is sent through the motor’s spinning electromagnetism and then converted back to DC as it leaves the motor as a form of propulsion. Because an electric motor produces an instantaneous amount of torque, it has a much more responsive driving experience than a combustion engine. This can be a lot of fun when you’re driving, but it’s important to remember that the car isn’t built for sudden acceleration. You’ll get better fuel economy if you use the accelerator more gradually. If you remember these basics of what is going on inside an electric motor, you can drive with more confidence and efficiency.