Triple solid slot Zero 75-7

Electric Motors and Controllers
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Farfle   1 MW

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Triple solid slot Zero 75-7

Post by Farfle » Jun 05 2015 10:37pm

Hello all! I have an exciting project to share with you!

So, Farasis purchased the DP1E (the zoomy portland-made carbon fiber track car that Luke, myself and a handfull of others raced at refuel last year)

Anywho, right now Its got a crappy Remy HVH250 that makes a super lame 100KW and needs a really dumb 300 volt battery to get said lame power. So, leveraging some already amazing motors, I am making a six-wide 75-7.

The stock 75-7s are 6 turns of 24 paralell strands of 18Awg.


This motor will be a 75-42 by zero's nomenclature and because its six stators wide, i am keeping the same Kv and reducing the turn count to a single turn. One turn of 144 paralleled strands, which will be divvied up into 6 24 strand groups each going to its own 420A controller. This should result in about 300hp to the shaft and not at lethal voltages. it just takes 2.4 KA to do it, which is a simple thing to do instead of designing in three times the failure points in BMS's and such.

Today, I got the stator lamination stacks removed from six 75-7s. We used an end mill to score the cases until they fractured open (Surprised me first go-round, they must be a pretty good press-fit), then we pried them open and they pulled right out.

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Last edited by Farfle on Jul 06 2015 10:23pm, edited 1 time in total.
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flathill   100 kW

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Re: Sextuple Zero 75-7

Post by flathill » Jun 06 2015 2:12am

might want to use triple or quad thickness insulation on the mag wire to reduce chance of interwinding shorts
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Last edited by flathill on Jun 06 2015 12:50pm, edited 2 times in total.

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liveforphysics   100 GW

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Re: Sextuple Zero 75-7

Post by liveforphysics » Jun 06 2015 2:15am

Re-use is the most efficient form of recycling. Thank you kindly for processing our test scrap in an environmentally responsible way that can be beat for amazing performance! The DP1e will finally be a reasonable man's vehicle with >300hp and less weight. ~1250lbs? :-)
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John in CR   100 GW

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Re: Sextuple Zero 75-7

Post by John in CR » Jun 06 2015 11:12am

Sounds awesome. Doesn't the extremely low inductance concern you?

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Farfle   1 MW

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Re: Sextuple Zero 75-7

Post by Farfle » Jun 06 2015 11:27am

Got the windings pulled from the stator this morning.

A sawzall to rip the end turns, followed by a flap disk to grind it flush, and then a punch knocks the windings out.

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Farfle   1 MW

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Re: Sextuple Zero 75-7

Post by Farfle » Jun 06 2015 11:29am

John in CR wrote:Sounds awesome. Doesn't the extremely low inductance concern you?
1/6 the turns, means 1/6 inductance, but because there is 6x the stator, you get Six 1/6ths and it all cancels out. :wink:
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Nuts&Volts   100 W

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Re: Sextuple Zero 75-7

Post by Nuts&Volts » Jun 06 2015 6:46pm

This is awesome. Will you be reusing the rotor assemblies? With about 420 ftlbs i think the 1" shaft on the rotors would be just fine as long as it's a high strength steel

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Farfle   1 MW

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Re: Sextuple Zero 75-7

Post by Farfle » Jun 06 2015 8:24pm

Nuts&Volts wrote:This is awesome. Will you be reusing the rotor assemblies? With about 420 ftlbs i think the 1" shaft on the rotors would be just fine as long as it's a high strength steel
The stock rotors will be put on a piece of ordinance grade 4340 steel shaft with a splined output. I dont want it being a weak point. Overbuilding a shaft is an easy place to buy reliability.
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nutnspecial   1.21 GW

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Re: Sextuple Zero 75-7

Post by nutnspecial » Jun 06 2015 8:56pm

Most of this is over my head, but becuase 'farfle' is a e-household name I'd like to offer my gratitude in my own limited capacity:
'You said ''sex'''! (ES is the coach and I'm the 'subject')
https://www.youtube.com/watch?v=gHmsReGYnCs :lol:

Seriously thanks though. And hi from a beginner.

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Farfle   1 MW

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Re: Sextuple Zero 75-7

Post by Farfle » Jun 06 2015 9:05pm

nutspecial wrote:Most of this is over my head, but becuase 'farfle' is a e-household name I'd like to offer my gratitude in my own limited capacity:
'You said ''sex'''! (ES is the coach and I'm the 'subject')
https://www.youtube.com/watch?v=gHmsReGYnCs :lol:

Seriously thanks though. And hi from a beginner.

Ahhaa never watched much B&B. And I am very happy to bring this project to you all :). I cant wait to stick it to all the HV systems when we do it better.
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Ohbse   10 kW

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Re: Sextuple Zero 75-7

Post by Ohbse » Jun 06 2015 9:22pm

Very cool indeed.

Given that you're going to one turn, wouldn't this be an ideal application for an extruded/pin type 'winding'? or are there disadvantages compared with conventional stranded stuff?

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Farfle   1 MW

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Re: Sextuple Zero 75-7

Post by Farfle » Jun 06 2015 9:38pm

Ohbse wrote:Very cool indeed.

Given that you're going to one turn, wouldn't this be an ideal application for an extruded/pin type 'winding'? or are there disadvantages compared with conventional stranded stuff?

If I had a super badass 2400A controller, It would already have TIG welded copper bars in it. BUT, I need to split it up into six seperate strands. So I haven't come up with a way to do that yet.
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Thud   100 MW

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Re: Sextuple Zero 75-7

Post by Thud » Jun 06 2015 10:28pm

Another soon to be Epic motor from the farfle team.
I'll be watching bud.
get some......

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major   10 kW

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Re: Sextuple Zero 75-7

Post by major » Jun 06 2015 11:14pm

Farfle wrote:
John in CR wrote:Sounds awesome. Doesn't the extremely low inductance concern you?
1/6 the turns, means 1/6 inductance, but because there is 6x the stator, you get Six 1/6ths and it all cancels out. :wink:
I think inductance is proportional to the square of the coil turns. Not sure how it all washes out :?

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Re: Sextuple Zero 75-7

Post by John in CR » Jun 07 2015 12:07am

Farfle wrote:
John in CR wrote:Sounds awesome. Doesn't the extremely low inductance concern you?
1/6 the turns, means 1/6 inductance, but because there is 6x the stator, you get Six 1/6ths and it all cancels out. :wink:
While Kv scales linearly like that, inductance doesn't. :wink: My quick and dirty comes up with a reduction in inductance by a factor of between 4 and 5, which is much less than I originally thought, so maybe it's fine. I don't know if FOC controllers have the same issues with low inductance as common trap controllers, so it may be a moot point.

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Farfle   1 MW

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Re: Sextuple Zero 75-7

Post by Farfle » Jun 07 2015 1:02am

It seems I am mistaken. Excellent.

Punching it into emetor with a different motor. I get

10mm Length 6t stator: .117. mH

60mm Length 1t stator: .0116 mH


This is a problem. I believe this motor is at the lower limit of what a Sevcon can run.
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liveforphysics   100 GW

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Re: Sextuple Zero 75-7

Post by liveforphysics » Jun 07 2015 1:06am

Farfle wrote:It seems I am mistaken. Excellent.

Punching it into emetor with a different motor. I get

10mm Length 6t stator: .117. mH

60mm Length 1t stator: .0116 mH


This is a problem. I believe this motor is at the lower limit of what a Sevcon can run.
They can handle a 4t.
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Punx0r   10 GW

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Re: Sextuple Zero 75-7

Post by Punx0r » Jun 07 2015 8:53am

I suspect I could be completely wrong here, but in calculating the new inductance, don't you need to consider that the winding area (as seen by each controller) has been reduced to one-sixth?

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Re: Sextuple Zero 75-7

Post by Lebowski » Jun 07 2015 11:57am

Each of your 6 controllers needs to know there are 5 others driving the same stator teeth, else your FOC won't be correct.

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Re: Sextuple Zero 75-7

Post by Nuts&Volts » Jun 07 2015 12:17pm

Lebowski wrote:Each of your 6 controllers needs to know there are 5 others driving the same stator teeth, else your FOC won't be correct.
The sevcon controllers have a master/slave setup that allows them to parallel up. I've seen two on one motor, but pretty no one has done 6 before.

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Re: Sextuple Zero 75-7

Post by Lebowski » Jun 07 2015 12:24pm

Nuts&Volts wrote:
Lebowski wrote:Each of your 6 controllers needs to know there are 5 others driving the same stator teeth, else your FOC won't be correct.
The sevcon controllers have a master/slave setup that allows them to parallel up. I've seen two on one motor, but pretty no one has done 6 before.
Is this only to share throttle information or does each controller how many others there are and what relative phase they have (whether they are on the same teeth or whether some are 30 degree offset ?) ?

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Re: Sextuple Zero 75-7

Post by John in CR » Jun 07 2015 12:59pm

A way to gain inductance is what the factory does with my motors, which in your case would be to wind it as 6 phase or go all the way and do it as 12 phase. 12 phase would be the best in terms of inductance, because each tooth gets more turns of copper for the same Kv. The end result is same total copper, same Kv (with the right # of turns), but a higher easier to drive inductance. With 12 phase you'd have to go with 4 or 8 controllers, since 6 wouldn't work.

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Re: Sextuple Zero 75-7

Post by neptronix » Jun 07 2015 1:44pm

Awesome project :)

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Re: Sextuple Zero 75-7

Post by flathill » Jun 07 2015 7:34pm

I have seen 4 on one motor so 6 should be possible. I still think interwinding shorts could still be a problem even with a master/slave setup (pwm sync) so be careful not to knick the insulation during winding

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Re: Sextuple Zero 75-7

Post by John in CR » Jun 07 2015 9:05pm

flathill wrote:I have seen 4 on one motor so 6 should be possible. I still think interwinding shorts could still be a problem even with a master/slave setup (pwm sync) so be careful not to knick the insulation during winding
One phase on each tooth and 4 controllers total eliminates that potential issue too.

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