# Electric Motor Question

Discussion in 'Sensors and Actuators' started by Yoa01, Jul 13, 2013.

1. ### Yoa01

214
0
Jun 18, 2012
Hi all,

I had this possibly stupid idea to figure out how to make an electric car. This isn't to say I will make one, but hey, everyone needs that one neat idea, right? Just for fun, I was thinking a 400-hp sports car.

I know that one could get a 100-hp motor for like \$4000 or so, and I figure if you have 4 of them you then have a 400-hp car (because simple math is always right, right?). Only problem I see with this is that most motors tend to be rated at a certain RPM, and cars tend to need variable RPM. How would one go about doing that? Could just a high-power potentiometer used as an attenuator on the power input on a pedal act as an accelerator? Then of course turns would be an issue given that wheels have to rotate at different rates. That could be made easier by using only 2 powered wheels, I suppose.

If you can't tell, I've never used an electric motor, so I have nearly no idea how they work. And yes, I do know that electric motors and required battery and possible other electronics (like a reverse switch or whatever) can weigh too much to make a viable car, but it's just an idea at the moment. I mean the braking system so far is just to let off the accelerator!

But seriously, if you know how motors work, know what kind would work best, and how to vary their speed, that would be useful, even for smaller motor projects. I build synthesizers, audio gear, and voltage processors; I have no experience doing this kind of work! Thanks in advance.

Edit: YAY 200th post!

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,496
2,837
Jan 21, 2010
Electric motors give high torque at low speed, so 4 100HP motors connected directly the the wheels would give you a lot of "get up and go".

The problem will be the batteries (weight and size) and the control.

No you can't use a large potentiometer.

There are a number of electric vehicle web sites and I'd suggest you peruse some of these.

Perhaps consider designs for electric bicycles first as they have many of the same elements, but at more manageable power levels.

3. ### Y2KEDDIE

259
15
Sep 23, 2012
Electric motor, Electric car

I would suggest using polyphase AC motors. They are smaller than single phase motors. Operate polyphase motors with a variable frequency drive, Speed and torque are a function of voltage X frequency. The motors should be inverter duty which means they are designed to run at higher temperatures and different voltages which stress the windings. The temperature increase in part is caused by running the motor at a lower speed thus reduced air flow (cooling).

4. ### Yoa01

214
0
Jun 18, 2012
I am totally cool with get up and go The batteries I know will be an issue, that's why I was thinking either Lithium Sulfide of Lithium Ion batteries, as they seem to have the best weight-to-energy ratio. I will look into such web sites, thank you.

Wouldn't higher temperatures and winding stress cause issues in the long run?