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  #1  
Old 05-30-2012, 09:21 AM
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Default Help with motor decision (Kostov vs NetGain)

I'm just starting my conversion (86 Porsche 944 Turbo) and trying to figure out my parts list/budget. I'm having trouble deciding between the NetGain motors and Kostov motors. I'm planning to have around a 240V nominal pack (could change one way or the other depending on motor), and hoping for better than stock performance.

Attached is a spreadsheet I started putting together (you'll see lots more than the motor options, ignore the rest it's all just notional). Can someone verify the stats in the motor section? I can't figure out how to compare apples to apples with these, since the NetGain specs give torque and such at one voltage/amp and the Kostov at another.

Any other big pros/cons for the two brands (or specific models) anyone can share??
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  #2  
Old 05-30-2012, 01:29 PM
somanywelps somanywelps is offline
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Default Re: Help with motor decision (Kostov vs NetGain)

You want the voltage above 300V to compensate for sag under acceleration. Especially with smaller kwh packs.
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Old 05-30-2012, 05:22 PM
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Default Re: Help with motor decision (Kostov vs NetGain)

Quote:
Originally Posted by somanywelps View Post
You want the voltage above 300V to compensate for sag under acceleration. Especially with smaller kwh packs.
Only if I get a motor rated for 250ishV right? A NetGain motor rated for 170V should be fine with a pack voltage at nominal 240V...
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Old 05-30-2012, 09:33 PM
ruckus ruckus is offline
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Default Re: Help with motor decision (Kostov vs NetGain)

Regardless of which one you choose, I would upgrade the brushes to Helwig from the beginning (Netgain is already doing this). This will improve you temp, power, and longevity according to recent tests at EVTV.

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Last edited by ruckus; 06-06-2012 at 08:09 AM. Reason: to send out positive vibrations
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  #5  
Old 05-31-2012, 06:26 AM
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Default Re: Help with motor decision (Kostov vs NetGain)

Quote:
Originally Posted by SCEV View Post
A NetGain motor rated for 170V should be fine with a pack voltage at nominal 240V...
Yes, but if you expect high performance you will need more than 170v (exept if you think about two motor).
From your first question, I was thinking that you only want to choose between Warp 11 HV and a Kostov Alpha.

Both motor will be impressive with proper battery pack.

Personnaly, I'm impress by the high efficiency of the Alpha (even at 500A). It's probably a good sign of what it can do at 1000A (or more).

But, the Warp 11HV have proof few time that it's a beast (Crodriver BMW, Valerun BMW)
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Old 05-31-2012, 07:08 AM
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Default Re: Help with motor decision (Kostov vs NetGain)

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Originally Posted by ruckus View Post
Why do your only options contain problematic and failure-prone brushes? Regardless of which one you choose. This will be the issue.

I would look at BLDC such as this before deciding.
http://www.greenstage.co.nz/PDFs/Scott_Drive_100.pdf
...
Uh-huh... Surely a Chinese motor controller will be the very paragon of reliability and performance in comparison...

Maybe this "Scott Drive" will be the exception that proves the rule, but as I pointed out in the thread about it, it's the same type of motor/controller as used in small computer fans - an application where low starting torque and high amplitude torque ripple (+/-15%) isn't an issue. In a traction drive, both of those downsides are objectionable, if not crippling.

I'd hold off on recommending this system until someone unbiased has actually tried it. On paper it doesn't look particularly impressive to me. $5500 for 80kW peak isn't any more powerful than the Curtis 1238 + AC-50, and it's actually more expensive than the latter system when purchased from a known good vendor like frodus here.
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Old 05-31-2012, 10:05 AM
ruckus ruckus is offline
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Default Re: Help with motor decision (Kostov vs NetGain)

Quote:
Originally Posted by Tesseract View Post
Uh-huh... Surely a Chinese motor controller will be the very paragon of reliability and performance in comparison...
I would actually recommend one of the MADE-IN-USA water-cooled brushless motors... Except, there are none for sale.

If you want air-cooled BLDC you can call Powertec. With typical american service they won't bother to call you back or even send you a price sheet with big numbers on it.

Quote:
Originally Posted by Tesseract View Post
Maybe this "Scott Drive" will be the exception that proves the rule, but as I pointed out, it's the same type of motor/controller as used in small computer fans - an application where low starting torque and high amplitude torque ripple (+/-15%) isn't an issue. In a traction drive, both of those downsides are objectionable, if not crippling.
Really? Then why has heavy industry shifted from brushed motors to BLDC? Again, Powertec and other BLDC documentation show very impressive starting torques so this argument seems a bit of a red herring.

Most electric motors don't have a torque problem, they have a hp problem. Especially inefficient air-cooled Brushed DC motors. Look at the specs, this motor weighs 54lbs LESS than the 11" yet is rated at 45+ hp continuous. Brushed motors just can't compete for long high-speed driving. How many OEMs use brushed motors? None. Hmmmm, wonder why?

Quote:
Originally Posted by Tesseract View Post
I'd hold off on recommending this system until someone unbiased has actually tried it. On paper it doesn't look particularly impressive to me. $5500 for 80kW peak isn't any more powerful than the Curtis 1238 + AC-50, and it's actually more expensive than the latter system when purchased from a known good vendor like frodus here.
It is called the Scott Drive 100 because the motor is rated at 100kw peak, not 80. They don't list a max wattage for the controller but it calculates to 200kva. According to the listed torque figures, the AC-50/Curtis is not in the same league. The "100" is the "derated" model. More power and voltage should be coming soon.

The Scott Drive system is currently installed and being used in several cars in NZ. Several thousand km and no problems reported. The controller is not Chinese, but made with quality in New Zealand.

I look forward to meeting you (I think your controllers are brilliant) at EVCCON where I will likely have a Scott Drive for display along with the "brushed" '37 Jaguar.

Cheers
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Last edited by ruckus; 05-31-2012 at 10:39 AM.
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Old 05-31-2012, 12:19 PM
DavidDymaxion DavidDymaxion is offline
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Default Re: Help with motor decision (Kostov vs NetGain)

Racers seem to prefer the Netgain motors. Kostovs are a bit cheaper. I think interpoles are a plus, all the Kostovs have interpoles but just one of the netgain motors do. I have a Kostov 11 alpha, sepex wound on order.
Quote:
Originally Posted by SCEV View Post
I'm just starting my conversion (86 Porsche 944 Turbo) and trying to figure out my parts list/budget. I'm having trouble deciding between the NetGain motors and Kostov motors. I'm planning to have around a 240V nominal pack (could change one way or the other depending on motor), and hoping for better than stock performance.

Attached is a spreadsheet I started putting together (you'll see lots more than the motor options, ignore the rest it's all just notional). Can someone verify the stats in the motor section? I can't figure out how to compare apples to apples with these, since the NetGain specs give torque and such at one voltage/amp and the Kostov at another.

Any other big pros/cons for the two brands (or specific models) anyone can share??
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Old 05-31-2012, 01:41 PM
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Default Re: Help with motor decision (Kostov vs NetGain)

Quote:
Originally Posted by SCEV View Post
Only if I get a motor rated for 250ishV right? A NetGain motor rated for 170V should be fine with a pack voltage at nominal 240V...
Yep - 240V is plenty of voltage to maintain a nice, flat power band with a NetGain advanced timing motor. You might want to run 300V+ if you choose one of the highest voltage Kostov motors, or the interpoled WarP-11HV, but then you won't want to push as much peak current through them (no free lunch - higher voltage tolerance generally means lower current tolerance).


Quote:
Originally Posted by ruckus View Post
I would actually recommend one of the MADE-IN-USA water-cooled brushless motors... Except, there are none for sale. ...
Au contraire... the Remy HVH250 is made in the USA, is liquid cooled and can be purchased retail from: http://vaxosystems.com/store/category/53-motors.aspx

Quote:
Originally Posted by ruckus View Post
It is called the Scott Drive 100 because the motor is rated at 100kw peak, not 80.
You might want to take a closer look at the PDF you linked to above. If you multiply the peak voltage and phase current ratings for the motor - even assuming that both are RMS (DC equivalent) values - that's still only 67kW of peak power (320V * 121A * 1.73).

NB - I didn't respond to the rest of your post because it was mostly you trying to prove AC is better and who am I to argue otherwise?
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  #10  
Old 05-31-2012, 01:57 PM
somanywelps somanywelps is offline
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Default Re: Help with motor decision (Kostov vs NetGain)

Quote:
Originally Posted by DavidDymaxion View Post
I have a Kostov 11 alpha, sepex wound on order.
I was wondering about this. Who did you order it from?

(Also what controller are you planning (I'm waiting for one that's not out yet))
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