How do electric cars produce maximum torque instantly?


Most electric cars aren't normally associated with performance, but they are able to achieve something gasoline-powered cars can't: peak torque at zero rpm.

It's thrown around often, and many will comment on how quick an electric car feels around town thanks to maximum torque delivered instantly. If in doubt, just take a ride in a Tesla Model S and ask the driver to drop the hammer.

But how does an electric car achieve this? Jason Fenske from Engineering Explained is back to make sense of the gadgetry going on. Foremost, it's important to realize there isn't an engine under the hood of an electric car. Instead, there is a motor-generator, and a battery pack to supply power. As the electric current travels through the motor within a magnetic field, it generates a force. The more current applied, the more the motor will spin.

A generator does something similar, but the direction of the electric flow is reversed: rather than taking in current to spin the armature, the armature is spun through the field by the deceleration of the vehicle. This produces electricity, which is used to recharge the battery, and the motor can switch between powering the car and regenerating electricity as fast as the driver can accelerate and lift off.

As the motor revs increase, however, it also creates what's called "back electromotive force" or "back EMF." The faster the motor spins, the more back EMF is created, reducing the effective voltage it can deliver. 

But at zero RPM, all of the electricity the motor creates from the time electric power is applied becomes instant torque—without any back EMF to reduce its output. The higher the revs, the more back EMF, meaning that instantaneous torque effect diminishes.

It's this effect that gives, for example, the rather mundane Chevrolet Bolt EV the power to scoot away quickly from a stoplight. It's not jaw-dropping amounts of torque, but the maximum output on tap from zero rpm does create a more entertaining drive. Grab all of the knowledge surrounding electric motors in the video above.

 
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