Electric vehicle motor weight

Barbqranch

Senior Member
Location
Arcata, CA
Occupation
Plant maintenance electrician
I see that an ordinary 3 phase 500 hp motor weighs over a ton. I understand Tesla and perhaps some other electric vehicles claim to produce more than 500 hp. How do they get the weight down? Is it simply that they overload the motor, knowing that once it gets to speed, it will use low 2 digit power (like my Karman Ghia w/ a 35 hp engine)?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
"HP" is a function of torque at a given speed. A 500HP AC induction motor is giving out xxx torque at 1800 RPM CONTINUOUSLY. For things like EVs, the motors cannot deliver the peak torque at a speed that equates to 500HP for an unlimited amount of time, just like an IC engine cannot. It will over heat. But in a car, you don't NEED all 500HP continuously, you only need it to accelerate, regardless of how you attain it. In an AC motor, PEAK torque is actually around 200-250% of the rated CONTINUOUS torque, and because the EVs use the equivalent of a Vector Drive to run the motors, they can deliver that torque almost instantaneously. So if you wanted to equate a Tesla motor to a standard AC induction motor, its more like a 150-200HP motor. Then add to that the design has liquid cooling going to an external heat sink system, and the physical size comes down even more.
 

GoldDigger

Moderator
Staff member
Add to that that an AC motor directly across the line has a large magnetizing current even at zero load, and although that does not require much power it still causes resistive heating in the motor windings and
magnetic losses in the rotor.
 
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