T&L Publications

Hello all,

I am in the process of making a Bar Stool Racer (BSR)

I'm looking at motors and finding there are a lot of 3 phase motors with the HP that I want.

My BSR will be electric and I wanted to know if there was a circuit or device out there that
can take 24V DC and convert it to 120V to 230V AC 3 phase and be able to switch on/off

Thanks in advance!

Tony

UPDATE
I'm reading this right now
http://www.instructables.com/id/250-to- ... -Inverter/

Are you sure you want to go that 3-phase route? Adds complexity to a........bar stool?
DC motors and controllers would be way simpler, and commonly available.
You should compare overall losses of DC vs. conversion to 3 phase too.

Sambuchi,

24 VDC? Sounds like a starter for diesel. They would have more than enough torque and HP to rip that stool
out from under you. You'd just have to figure out a way to keep it cool enough to run for extended periods,
long enough for a race. I would think that would be more efficient than upconverting.

YouTube has a bunch of BS races available. They look like a blast.

Good luck with whatever method you choose.

CeaSaR

jwax wrote:Are you sure you want to go that 3-phase route? .

I know! I just caved and bought a 6hp go cart for 100.00 I will use the parts for my BSR.

Its amazing how cheap a gas motor is to an equivalent electric motor.

I would have love to get my "EV project" out of the way here, but it will have to wait. Maybe some other day!

Here is a link i was quite envious of...
http://www.engineeringhobbyist.com/proj ... ool_racer/

But you can pretty much build a BSR for the price of that motor!

DC motors are torquey things! 15 HP on that machine without outriggers would be nuts!
I had put a 1 HP DC motor in a gokart, with a Curtis controller and 4 12 volt deep cycle batteries to tool around the neighborhood at a rather quiet 45 mph!

Certainly you could build a 3 phase inverter (might even find one out there) but the current needed from the DC source will be very high.

How much current does a 3 phase 240V ??HP motor use. Take that and multiply it by 10 for a ballpark. (not sure how 3 phase alters the conversion right now and frankly don't care). I'm thinking you might need 30-60A just to get moving. The higher current will add considerable extra cost in the form of high power FETs for the inverter and heavy gauge wire all around. You will probably need a bank of batteries to get a decent ride.

Before you go all off on solutions to convert power for a given motor, you should run the numbers of current, power and battery capacity to learn how much battery you will need to carry for a given range and curb weight. Lots of physics formulas here. Those calculations should be at the heart of every EV project. When you're done, write an article for N&V. A tutorial on energy use for EV would be useful to many.

Hi,


Just to note, you'll be needing about 31 amps for every horsepower your motor is,
from a 24v source. Thus, if your motor is 2 hp you'll be drawing 62 amps from a
24v source.

This is all great info.

I was about to hit the buy button on gas go cart till I read this thread last night.

I found some reasonable 1HP 1000W motors on the net. I dont know the RPM yet or the torque
on them . I guess on thing to consider is a clutch to get it going. I still have a lot to think
about before I dive in... giving myself the week to study.

Clutch? We don't need no stinking clutch! You only need a gear (or chain) reduction to convert 2 or 3 thousand motor RPM's to a few hundred RPM's at the drive axle.
An electric treadmill usually has a several HP motor, and control circuitry. Sometimes found for cheap, or free!

For 3 phase from 24V d.c.
Look into brushless D.C. motor controls used in hobby applications.
They are available in many sizes.
Usually only fractional H.P. at 24 volts but are 3phase.
Hope this helps.
Bygar