Triple solid slot Zero 75-7

Farfle

Farfle

100 kW
Joined
Jun 27, 2010
Messages
1,759
Location
Redmond OR
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.











 
might want to use triple or quad thickness insulation on the mag wire to reduce chance of interwinding shorts
iiS84hOJXh1Pq.gif
 
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? :)
 
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.




 
John in CR said:
Sounds awesome. Doesn't the extremely low inductance concern you?
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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:
 
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
 
Nuts&Volts said:
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
Click to expand...

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.
 
nutspecial said:
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.
Click to expand...


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.
 
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?
 
Ohbse said:
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?
Click to expand...


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.
 
Another soon to be Epic motor from the farfle team.
I'll be watching bud.
 
Farfle said:
John in CR said:
Sounds awesome. Doesn't the extremely low inductance concern you?
Click to expand...

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:
Click to expand...

I think inductance is proportional to the square of the coil turns. Not sure how it all washes out :?
 
Farfle said:
John in CR said:
Sounds awesome. Doesn't the extremely low inductance concern you?
Click to expand...

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:
Click to expand...

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.
 
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.
 
Farfle said:
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.
Click to expand...

They can handle a 4t.
 
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?
 
Lebowski said:
Each of your 6 controllers needs to know there are 5 others driving the same stator teeth, else your FOC won't be correct.
Click to expand...

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.
 
Nuts&Volts said:
Lebowski said:
Each of your 6 controllers needs to know there are 5 others driving the same stator teeth, else your FOC won't be correct.
Click to expand...

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.
Click to expand...

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 ?) ?
 
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.
 
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
 
flathill said:
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
Click to expand...

One phase on each tooth and 4 controllers total eliminates that potential issue too.
 
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