# 11" Kostov Motor Constants?



## major (Apr 4, 2008)

Overlander23 said:


> Is it is as simple as looking at the performance graphs and dividing torque by amps?


Hi Over,

No, not quite so simple with wound field motors, especially series wound. Look at my post http://www.diyelectriccar.com/forums/showpost.php?p=140628&postcount=4 This shows the motor constant, K. Also used in the equations is Flux. The flux changes in the series motor depending on the load.

So simply dividing torque by current will yield a load dependent motor constant. Which then isn't really a constant, is it?

Regards,

major


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## Overlander23 (Jun 15, 2009)

Thanks for equations, major. So, does anyone know the construction details of the 11" Kostovs? Hehe... I've just emailed Kostov themselves, so we'll see what they come up with.


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## Tesseract (Sep 27, 2008)

The guys next door to us at Rebirth Auto just installed a Kostov 11"/192V in their demonstration vehicle (a '64 (I think) VW bug) so if you want specific pics or tests we can probably oblige. It's only a 120V system but they did spring for a transaxle-obliterating Soliton1 controller.... 

Anyway, my personal opinion so far is that the cheaper price of the Kostov 9"doesn't compensate for it's lower efficiency compared to the NetGain WarP 9, but the Kostov 11" is definitely worth considering.


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## Overlander23 (Jun 15, 2009)

Well this 11" Kostov would be going into a 1971 Land Rover, and using your Soliton-1. I'm just wondering what the differences are, practically, between the 192v and 144v versions.

If I'm looking for a 30kwh system, I believe it probably makes sense to go with the 192v motor. I believe either the 144v or the 192v will make more than enough power for the application. So the way I'm figuring it, I either slap in 23kW/h of battery and go for the 144v system (45 x TS160Ah) or go with 31kW/h (60 x TS160Ah) with the 192v system and get more range with a 150lb weight penalty.

If I had the motor constants I could plug them into this spreadsheet and get a better idea of... things...

Tesseract, any particular reason they're running 120v on the 192v motor? Just to get the lower rpm? In other words, why not the 144v? Wouldn't that be more efficient?


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## Tesseract (Sep 27, 2008)

Overlander23 said:


> Well this 11" Kostov would be going into a 1971 Land Rover, and using your Soliton-1. I'm just wondering what the differences are, practically, between the 192v and 144v versions.


The only difference might be 1 or 2 more turns in both the field and armature coils for the 192V version. I, as usual, defer to the most mighty and excellent expertise of major when it comes to all things motor 




Overlander23 said:


> Tesseract, any particular reason they're running 120v on the 192v motor? Just to get the lower rpm? In other words, why not the 144v? Wouldn't that be more efficient?


They had (<- note past tense) a 144V 9" Kostov, but Seb zorched it on the dyno not even a minute after calling me a big pussy for not pumping more power into it. I warned him a motor wound for higher voltage wouldn't take the same amount of overload current for the same amount of time as the WarP 9, but he never listens to my dire warnings of doom (e.g. - like when I told him setting the motor current ramp rate to 25000A/s would just break stuff, so he did it anyway and promptly cracked open the transaxle).

Anyway, the Kostov 192V/11" was being held in reserve for a larger demo vehicle, but because he zorched the Kostov 9, and I wanted the Warp 9 for the dyno (to be able to reliably test each Soliton1 at 1000A) he put the grossly oversized Kostov 11" into the Bug. THAT's a hilarious sight for sure.

Also, the Bug was the first vehicle that Rebirth Auto converted, and back then Seb was more or less following the advice of books that were written in the 80's when the only technology available for EV conversions was essentially golf cart stuff. In true Seb fashion, though, these books mostly recommended 72V or even 96V (for _real_ performance!  ) so he thought he was going to have a real barn-burner upping the voltage to 120V!

I know at some point he's planning on switching the Bug over to a higher voltage lithium system, but right now we are all a little swamped... He's got a couple of conversions to wrap up, a twin motor dyno to build, and some other odds-n-ends while I have to both set everything up to produce the Soliton1 in higher volumes and actually make them in the meantime.


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## Bowser330 (Jun 15, 2008)

Tesseract said:


> The only difference might be 1 or 2 more turns in both the field and armature coils for the 192V version. I, as usual, defer to the most mighty and excellent expertise of major when it comes to all things motor
> 
> 
> 
> ...


Well it sounds like you and your team are pretty busy which is a good thing, I would be concerned if you weren't! Congrats on all the orders..hopefully the funds will be re-invested into additional test vehicles with data logging and possibly dyno charts???


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