Please help me with motor windings!

[Mozart]

Please help! I'm trying to understand what am I doing wrong with this motor that I've wind...

http://endless-sphere.com/forums/viewtopic.php?f=10&t=36945&start=30

Why is it so difficult to make a motor for ~50volts 220amps , I don't get it...
I was ready to pay a workshop to do the winding for me,but they ask me for the previous specifications of the motor!
And that does not exist! It's a new and custom stator that I need to make(or maybe remake cause I already made one!).
Can anyone please help me with the details?

 

[John in CR]

Start by going back to the wire and stator calculator and getting the inputs right. eg That's obviously not a 50mm diameter stator unless you have the tiniest hands I've ever seen.

I could be wrong, but I seriously doubt the stator laminations are of sufficient quality to enable that size to handle 11kw, especially since it was designed for a 41 turn winding. Such a small size would require very high rpm, which thick low quality lams won't support due to high iron losses. Assuming that it was a 12V generator before, then I think what your low winding count has done is turn it into a few volt motor due to the much higher Kv, but it will handle much higher current than the original.

Did you try running it as a motor with the original windings?

 

[Jeremy Harris]

I've tried to make a motor out of a motorcycle alternator - it's not really worth the effort, TBH. The laminations are usually really thick (often around 0.5 to 1mm thick) and the core losses are high at any reasonable rpm. They are usually wound to deliver at most a few hundred watts, and designed accordingly. The law of reciprocity pretty much applies to these things, in that they are very unlikely to deliver more power as a motor than they could as an alternator.

You haven't got a hope of getting 11 kW from one, unfortunately, more like 500 W or so at best.

 

[Mozart]

Start by going back to the wire and stator calculator and getting the inputs right. eg That's obviously not a 50mm diameter stator unless you have the tiniest hands I've ever seen.

I could be wrong, but I seriously doubt the stator laminations are of sufficient quality to enable that size to handle 11kw, especially since it was designed for a 41 turn winding. Such a small size would require very high rpm, which thick low quality lams won't support due to high iron losses. Assuming that it was a 12V generator before, then I think what your low winding count has done is turn it into a few volt motor due to the much higher Kv, but it will handle much higher current than the original.

Did you try running it as a motor with the original windings?

Thank you very much for your answers John&Jeremy,
My God, sometimes I amaze my self with how distracted I get!
Point no1:
-Instead of the diameter I input the radius!
BUT,I corrected the diameter in the Drive Calculator and hopefully no other number changed!
Point no2:
-As you both are saying, the laminations are 1mm thick...and I understand this is bad for the efficiency of the motor.
Point no3:
-As I have shown on video on my build thread I tried to run it with the original winding and that didn't work with the Jeti ESC.

Question:
How can I calculate the MIN/MAX Voltage of the motor I've winded...?

P.S. I'm not giving up yet...

 

[Jeremy Harris]

Electrically motors don't have a minimum voltage, and the maximum voltage is really set by the maximum rpm that the motor will run at. Maximum rpm is determined by several factors. In simple terms the Kv of the winding and the supply voltage determine rpm, but if rpm increases beyond the point where core losses start to dominate then you may well find that they place an upper limit on it. Controllers also have an effect, as they have a maximum frequency at which they will still commutate the motor, and you can hit this with multipole motors running at a fairly low rpm.

In the case of these bike alternators, as standard they run fairly weak ferrite magnets, nothing like as powerful as the neodymium magnets used in the majority of motors we use. This tends to make the motor rpm higher for a given voltage, plus it means that the motor will only have a fairly low torque (torque being a function of motor diameter, winding current, gap between magnet and start and magnet strength, mainly). High rpm means rapid commutation, which means that the core losses increase (they are a function of the rate of change of the magnetic field in the stator from switching the windings).

 

[John in CR]

I'll throw a WAG out there and guess that it's now a 1s motor. What I don't know is if the single cell is nicad (1v) lead acid (2v) lifepo4 (3V) or lipo (4v)

As a generator is was what 15-16V for charging a 12V battery? You changed the winding count from 41 turns to 6 turns or about a 7:1 reduction. 15/7 is about 2V, so maybe a 1s parallel group of A123 lifepo4's might be within reason. Will your controller go that low?

I know you're probably disappointed, but I'm interested to see what happens. I could actually use a 1hp 3volt motor, though I need a smaller diameter, so I hope you can spin that baby up. The copper looks like better than I could do as a 1st effort, and from Thud's description of painful winding you definitely deserve some joy out of the thing. Regardless I'm sure you learned a lot, so that's what really matters, and the next one will be even better. That's my approach and as a result I've been riding an ebike sucking up 30kw at 30mph but haven't blown a controller in a year, and while I rely on industrious Chinese laborers to wind the motors, I've invested serious amounts of time learning the little bit I need to know to get to ride that monster ebike.

John

 

[Mozart]

I'll throw a WAG out there and guess that it's now a 1s motor. What I don't know is if the single cell is nicad (1v) lead acid (2v) lifepo4 (3V) or lipo (4v)

As a generator is was what 15-16V for charging a 12V battery? You changed the winding count from 41 turns to 6 turns or about a 7:1 reduction. 15/7 is about 2V, so maybe a 1s parallel group of A123 lifepo4's might be within reason. Will your controller go that low?

John

I did a test run of the motor with 12s 3p Lipo 15Amph 30c and it was going great. I didn't take it at full speed though cause after ~4000rpm I got a little scared with the power it was turning!
So then I did something reeeaaally (and not really) stupid, I put my foot on the motor as a load...So the small 60amp fuse exploded, and when I changed in and turned it on again, the switch burned in the closed position and a rush of black smoke came from the ESC...

So now I will reconnect the windings in WYE and try again with a small Golden Motor E-bike controller...(this time without putting my foot on the motor...)