75-5 ZERO MOTOR REWIND

Doctorbass

100 GW
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Quebec, Canada East
From the project of this original thread: ZERO XU 2013 to 50hp ZERO FX conversion
https://endless-sphere.com/forums/viewtopic.php?f=10&t=115877

I have made some calculations about the motor rewind.

This 75-X plateform ( 75-7 and 75-5) seem to have 6 turns per tooth. I know that the 66V hybrid version of the 75-7 is having 4 turns per tooth and not 6. ( This hybrid have been offered to old 2012 Zero owners for replacing the me0913 in the past)

DATA:
Also i have the info that the 4 turns saturate at 1200A and the 6 turns saturate at 800A
The 6 turns have 24 strands of 18 gauge. I guess that the 4 turns should have 32 parallel strands to keep the same copper fill.
The 4 turn is for 66V and the 6 turn is for 102V
That's 17 Volt per turns

If i want to run 74V then in theory i would need 4.35 turns, and it's not possible as turns must be integer number usually (i think)

So i would need to keep 4 turns and the motor would be 68V nominal ( 17 x 4 = 68)

I would probably need a bit less field weakening then to run it 6500rpm using 74V nominal battery

So.. for 4 turns i would need 32 strands of 18 gauge.. But i dont have 18 gauge in stock..

I only have 14 gauge.

So.. I would need 12 or 13 strands of 14 gauge to be equivalent to the calculated 32 stands of 18 gauge..
( Equivalent to one gauge 3)

My question: is there any disadvantage to rewind a motor with larger diameter strands?

Doc
 
If you can find a controller with more phase current, perfect time to go 3 turn. This is because normal base speed without field weakening for 6t on 28s is ~4200rpm(I think).
 
liveforphysics said:
If you can find a controller with more phase current, perfect time to go 3 turn. .

I plan using one of my BAC8000 and max it out.

The last specsheet 2022 from october mention it is now max 86V instead of 90V so i will use 20 or maybe 21s ( if at 4.15V)
The max batt current is also mentionned to be 730 bA so with a sag to his nominal or a bit above it wold be let say 78V and 730bA i would get about 57kW max.

Did you tried running one at full 860 pA ?

If i run 3T than i would not need field weakening but for the same 860pA i would loose 25% torque but extend powerband as the full 860pA wold be used for torque generation and zero for field weakening as no need for it.

I am not sure what is the best trade off between 3 or 4T with a BAC8000.

There is no BAC16000 in the pipeline at ASI from what i know my friend :lol: I wonder what BAC model would be equivalent to the FARDRIVER 2400 in term of TRUE phase amp... A BAC24000?

Doc
 
I agree with you.

How about rewind with an isolated pair of 3T windings, then power it from a pair of BAC8000.
 
Hmm sound like The ARLO mod as you know!! :D



[youtube]3eL0EMFPnVw[/youtube]


Doc
 
Only costs you an extra controller, which is small and light to fit on the bike.

Get 3T RPM range and 6T torque for your second controller. A lot of powerband gains for carrying some extra silicon and copper phase leads.
 
The single controller idea i see as a temporary loss of sanity Doc. I for free will send you a second BAC8000 my friend to help you find rationality my friend.

You have no excuses in asking for higher phase current controller options if you would choose not to double phase current by running a second controller when they are so small and light for each BAC8000. Most powerband improvement on your project in return for a few pounds of aluminum and silicon.
 
Doctorbass said:
liveforphysics said:
If you can find a controller with more phase current, perfect time to go 3 turn. .

I plan using one of my BAC8000 and max it out.

The last specsheet 2022 from october mention it is now max 86V instead of 90V so i will use 20 or maybe 21s ( if at 4.15V)
The max batt current is also mentionned to be 730 bA so with a sag to his nominal or a bit above it wold be let say 78V and 730bA i would get about 57kW max.

Did you tried running one at full 860 pA ?

If i run 3T than i would not need field weakening but for the same 860pA i would loose 25% torque but extend powerband as the full 860pA wold be used for torque generation and zero for field weakening as no need for it.

I am not sure what is the best trade off between 3 or 4T with a BAC8000.

There is no BAC16000 in the pipeline at ASI from what i know my friend :lol: I wonder what BAC model would be equivalent to the FARDRIVER 2400 in term of TRUE phase amp... A BAC24000?

Doc
Hi, I would like to know if you could send me that specsheet for the bac 8000?
 
liveforphysics said:
The single controller idea i see as a temporary loss of sanity Doc. I for free will send you a second BAC8000 my friend to help you find rationality my friend.

You have no excuses in asking for higher phase current controller options if you would choose not to double phase current by running a second controller when they are so small and light for each BAC8000. Most powerband improvement on your project in return for a few pounds of aluminum and silicon.

Ah ha! Luke you are awsome. I guess both can be in sync with the same hall signal right? Then a dual 3T would be incredible. I remember Biff told me 1200pA max before stator saturation on the 75-7 ( 7cm stator width) hybrid 4T and 800pA for the 6T regular.
Any idea for the 75-5 (5cm)saturation point on regular 6T? I guess it s double on 3T..but what numbers?

That said are you planning dual fardriver2400?😯
Doc
 
Only Amp-Turns around the tooth impacts the magnetic circuit. Having a pair of 3t (go 4t) windings that gives the same % of slot copper fill, will let you drive 850Amps phase into each of the 3T windings, giving the torque of a 6t motor with 850Amps phase. The big difference will be the 3t double controller option will hold that tooth saturation torque clear up to max RPM (but will of course be drawing proportionally more battery power to produce that much higher HP out).

***Update*** for motor controller current loop stability reasons, 4T is a better choice than 3T.
 
j bjork said:
You who know these motors well, what is the phase resistance on the 75-7?

5.5mOhm for OEM 75-7

I recently learned 3T is not friendly enough to controller current control loops, and dual 4T windings is as low as ideal. I will update my post above recommending dual 3T to recommended dual 4T.
 
j bjork said:
Thank you, is that phase connection to phase connection with a wye connection between?
So actually 2 phases in that case.

That's correct, Wye termination, and phase to phase resistance.
 
Doctorbass said:
From the project of this original thread: ZERO XU 2013 to 50hp ZERO FX conversion
https://endless-sphere.com/forums/viewtopic.php?f=10&t=115877


My question: is there any disadvantage to rewind a motor with larger diameter strands?

Doc

Assuming you can get the same copper fill with thicker wire, the disadvantages of thicker are difficulty of winding, greater chance of stator insulation damage, and possibility of your end turns being taller and contacting the housing.

high pwm frequency favors thinner conductors due to skin effect though. 24khz pwm would have a roughly 0.4mm skin effect, whereas 14ga is 0.8mm radius. The inductance of the motor will smooth the AC component though, so it's going to require testing to see if the motor resistance changes between DC and your controllers pwm frequency.

Personally, I would not choose to wind a motor with single 14ga. It will be a huge pain in the ass, will require tamping each layer, and without winding a partial phase to test reactance its unknown whether skin effect will be a concern.
 
Thanks you John,

That is exactly the answer i needed. I was also worried about skin effect as well as wire emal dammage.

I have 22 gauge and 14 gauge wire roll with emal so two difficult possibility..

I think that 14 gauge is probably better suited for big primary of a Tesla coil project, or transformer rewound. Or selling it and buying 18 gauge instead...

Doc
 
Keep in mind, skin effect frequency is only of the current waveform. This means it's not the 16-30kHz current control loop frequency that matters, but the commutation frequency (400-700Hz peak typically). That let's pretty fat wires or bus bar style windings get pretty thick before skin effect plays a roll.
 
liveforphysics said:
Keep in mind, skin effect frequency is only of the current waveform. This means it's not the 16-30kHz current control loop frequency that matters, but the commutation frequency (400-700Hz peak typically). That let's pretty fat wires or bus bar style windings get pretty thick before skin effect plays a roll.

Ive wondered if the inductance of the motor would always block the pwm frequency , but haven't measured enough motors to make the concrete assertion. If that's always the case, then just wind it with the 14ga and watch the force and sharpness while bending around the stator edges. Game on!
 
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