[major]

I have an opportunity to acquire a Baldor industrial motor, model CP3773T. This has the following specs:

15HP, 480V, 18 AMPS, 3450RPM, 60HZ, shipping weight 226 Lbs.

The seller is asking a very, very low price. I am curious as to whether or not I could apply this to an EV conversion.

Assuming that I can acquire or invent a controller (which I can), can a motor like this be run at, say, 120-180 Hz for extra power and top speed? Would modifications would be necessary and, if so, what are they?

Hi mr,

For a 480 VAC motor you'll need like a 650 VDC battery. Possible for an EV, but using a 230 VAC requiring a 320 V battery is easier.

Also, I recommend using a 4 pole motor, so look for 60 Hz speed around 1750 RPM.

It is possible to run induction motors at higher speed with higher frequency. But if you are unable to proportionally increase voltage with frequency, you'll lose torque above base frequency and therefore not get increased power due to increased RPM.

Modifications to the motor? Rewind and cooling system. Maybe balance and bearings.

You seem to treat the inverter lightly. This can be a challenging task even for those skilled at it. See if you can find etischer's build thread and search this site for other ACIM discussions.

Regards,

major

 

[few2many]

Hey mr, I have a baldor 30hp, 1760rpm motor that is 230 or 460 volts. All the searching I have done has lead me to consider an industrial inverter. There are also threads about lowering the voltage, but that doubles the amps. Rewinds are expensive and the amount of battery needed is crazy.
Have you considered an ac kit like from hpgc, ev components or thunderstruck? Although I have a motor, I'm considering one of these kits.

 

[mriches]

Hmm this is all good food for thought. Some re's:

Battery size

I'm thinking of replacing the entire gas tank with one huge battery. I'd like to see how much kWh I can store in my car without going over $5k at the very most. So a really cheap motor that takes lots of volts sounds like it might be OK - but at the same time, if there are far more efficient motors out there, then I suppose it wouldn't be very smart for me to choose this Baldor. How does the Baldor compare in efficiency to some other AC motors people are using?
​

4 pole motor

Why exactly do you recommend a 4 pole motor? What are the advantages?
​

Invertor

I'm not trying to treat it lightly, but I do want the focus of this thread to be on the motor choice. Certainly the invertor can affect that but I see a few other threads on here where the invertor discussion has hijacked the entire thread, I don't really want that.
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AC kits

I've considered them, but I think I can put together something as good or better than a kit using basic components and my own brain power. Plus, where's the real challenge in assembling a kit? I might as well build another robot out of Legos at that point. I'd rather make something that's truly my own. More work, but more reward, as well.

FWIW, if I can't find an AC motor that I can afford, I plan to use something similar to the TransWarp 9 DC motor. I'd really hate to have to do that though because I have some really good ideas I'd like to use to make a vectored drive controller.
​

 

[mriches]

P.S. the "m" in my alias is short for Mike.

 

[samborambo]

You may not need to completely rewind the stator to lower the voltage. I many instances you can halve the voltage, etc by reconnecting the stator pole pairs in parallel instead of series. There was a good discussion on the AEVA (IIRC) about this including diagrams for reconnecting a typical 2 pole motor.

Simply reconnecting the terminal box for delta is probably not an option for you. Typically with motors over about 5kW the "normal" phase connection is delta to allow delta-wye switching for starting the motor direct on line (DOL). Switching it to wye reduces the inrush current when the rotor is at stall. Below 5kW, soft starting a motor isn't needed and the motors are normally connected in delta. When reconnected in wye, they can run at full rating on a single to 3 phase inverter due to the matched input voltage.

Lastly, if you have to have a full rewind done, it's not astronomical. A local motor rewinder here last week quoted be around US$650 to rewind a 15hp motor for a custom voltage.

Sam.

 

[major]

4 pole motor

Why exactly do you recommend a 4 pole motor? What are the advantages?
​

Hi Mike,

How many 2 pole motors do you see used in EVs? 4 pole motors have better torque density. Advantages are primarily thinner yoke and shorter end-turns. You can carry this further and look at 6 or 8 poles. But frequency starts getting to you with high pole counts. 6 isn't bad, nor 8. I think the Toyota hybrid motors are 8 pole. But by and large, EV motors are 4 pole.

And Baldor? Maybe not the most efficient motor, but decent. I'd have no problem with Baldor efficiency. Not sure they make motors using aluminum housings, so may weigh in on the heavy side.

Regards,

major

 

[mriches]

samborambo and major: Excellent info, thanks!

 

[few2many]

Hey Mike

Plus, where's the real challenge in assembling a kit? I might as well build another robot out of Legos at that point.

Darn right!
Heres a link to someone who successfully halved the voltage of a 3 phase indutrial motor from 230 to 115. Mine is a dual volt motor I want to drop to 115v.

http://www.aeva.asn.au/forums/forum_posts.asp?TID=1237
lots of luck to ya and let us know what you have in mind.
We seem to have similar tasks at hand.