# 3 Phase Induction Motors in Cars.



## Dallus (Dec 7, 2011)

Hi, I've started researching electric cars more for my future project so by the time lithium-sulfur batteries are viable and my funds are plenty I'll have a good knowledge of everything.

So I've noticed most EV cars use DC motors, and I was wondering why 3 phase aren't used more, With a VFD and 2 or even 4 3-phase motors powering the car straight direct to wheel reducing the need for difs using the motors themselves increasing efficiency and reducing maintenance.

Just wondering, I've got more on the idea but yea would like some peer feedback on the idea.

Thanks.


----------



## Jan (Oct 5, 2009)

Hi Dallus, all your questions are discussed here on this website in great detail. From ac vs. dc, pro's and cons of direct drive, in wheel hubmotors (and why they never work), single speed gearing, efficiency at low RPM, unsprung weight, pro's and cons of keeping a clutch. Even how to use an automatic gearbox. Etc. It's all there. 

Some of these are discussed in the current page view, others can be found with the search engine.


----------



## major (Apr 4, 2008)

Dallus said:


> So I've noticed most EV cars use DC motors, and I was wondering why 3 phase aren't used more,.......


Hi Dall,

That would be most "DIY" EV cars. Because most (maybe all) production EV cars use 3 phase motors. Three phase drives (both induction and PM) require a bit more, hmmm, let's call it sophistication than DC drives. The controller is more complex and needs to be compatible with the particular motor. DC drives are less sensitive in this regard. There are also availability and cost issues which are big factors for the DIYer. In the past few years several companies have brought 3 phase controllers to market which are paired with motors by suppliers willing to sell to DIYers. These get up into the low to moderate power range for EV cars and aren't too cost prohibitive. A number of members here are using them.

Regards,

major


----------



## Coulomb (Apr 22, 2009)

Dallus said:


> I was wondering why 3 phase aren't used more ...


To cut a long story short, the main problem is the high voltage required for cheap industrial motors (around 400 VAC, so a battery pack of some 550 VDC at least), the desirability of "overvoltaging" a motor (hence even higher voltage again), and the lack of suitable controller/motor combinations for lower voltage. The Curtis 1238 controller with AC50/AC30 motor is the one exception, but it's arguably suitable mainly for lower end conversions (lighter, or lower performance).

As others have pointed out, the detail has been discussed at length; search for them if you want to know more.


----------



## tomofreno (Mar 3, 2009)

> The Curtis 1238 controller with AC50/AC30 motor is the one exception, but it's arguably suitable mainly for lower end conversions


 Hey, watch it, watch it!


----------



## Dallus (Dec 7, 2011)

Awesome that's allot of help on clearing up a few questions. 
I've got no problem with the advanced electronics side of things, I can get my hands on good inverters and VSDs, The only problem in the mechanics for me having a family fully of sparkies and no mechanics makes EV cars sort of a new challenge for us, Thanks for all the info you may hear from me later. 
Gonna go lurk the forum abit more.


----------



## Coulomb (Apr 22, 2009)

tomofreno said:


> Hey, watch it, watch it!


Heh, sorry Tom! 

Your SwiftE is a fine example of how the 1238 and AC50 motor in a small vehicle can give quite good performance. However, I think you'd agree that especially in a larger vehicle, it would probably lack the punch that a 9" motor, 144 V pack, and 700+ amp controller would have.

If only the forthcoming 144 V nominal Curtis AC controller would have a little more peak current capability, then we'd have a comparable AC system at reasonable cost.

But let's not ignite a DC vs AC war here. Let's just say that the one reasonably priced AC system (1238 controller with AC50 or similar motor) is positioned towards the lighter vehicle end of the market.


----------



## bjfreeman (Dec 7, 2011)

It depends on the level of DIY you are talking about.
I started with a couple of good articles that detail DIY.
www.metricmind.com/ac_honda/main2.htm
is more about the mechanical
http://etischer.com/awdev/
is more technical. BTW he went to work for Tesla


You can also look at *http://www.proteanelectric.com/*


*or you can get down and build everything from scratch.*


*I am more interested in HEV 
*


----------



## tomofreno (Mar 3, 2009)

> However, I think you'd agree that especially in a larger vehicle, it would probably lack the punch that a 9" motor, 144 V pack, and 700+ amp controller would have.


 Yep. Just joking around. My focus is different than most here. I like efficiency and reducing energy use. I was disappointed that the new Curtis AC controller will only do 500A. Told HPEVS I will likely wait to see if they come out with a higher current version later - like they did with the 7501/7601 controllers.


----------



## steven4601 (Nov 11, 2010)

Hi Tom,

wouldn't you be more interested in a higher voltage version ? 
This would allow to keep the motor longer in the constant current region.


----------



## gor (Nov 25, 2009)

idea is good - but not many can build controller for such motor, spend several years on r&d, trials & errors


----------



## tomofreno (Mar 3, 2009)

> wouldn't you be more interested in a higher voltage version ?
> This would allow to keep the motor longer in the constant current region.


 Little background: My present Curtis is max 130VDC input, this new one is supposed to be 160 to 170 max, so it is higher - to me. Yes 300V would be nice, but I already have a pack of 36 180Ah cells and I have room for 12-13 more, but not 60 more - sure would have range if I did! I suppose I could add smaller cells and just use half the capacity of the existing ones, but don't like that mix too much. HPEVS has designed a new motor for the new controller which has 150 ft-lb peak torque and 100 peak HP, so the new controller works well for them. Just not very well for existing motors like the AC50. I estimate 0 to 60 mph would take about 1 second longer for me with the new controller since I would have constant current to about 5k rpm, but 10% lower torque over about 4/5 of that rpm due to the 10% lower current of the new controller (presently I have constant current to about 4k rpm). So it would have been nice if they had squeezed out at least 10% more current. Maybe they will later.


----------

