My 4525 rewinding project

[omerco]

Something very small, and the meger didn't bother to beep. Also this happened only when heating the motor to 80+ degrees.

A year ago I rewinded a Quantum 4530 and the testing was the same. the motor runs strong until today, with a Kontronik 120.

[jamage]

You could say the thing is bedeviled, born under a bad Sun, and is in need of a sacred ancient purification ceremony to rid it of it's gremlins lol, but maybe there's another way.

When you say you fried the esc(s) something tells me your motor was pulling over 200 amps for more than 3 seconds. Is there a way to choke off that kind of draw before it gets to the esc? If I remember correctly after reading a full description on building motors of large proportions the y circuit will be seen as a short when the coil(s) is saturated, In many full scale motors they have both a y winding to get the motor up to speed (torque) and a delta (hp) to hold it there. That caught my interest as I'd never known y and delta can be mixed.

I'd try finding more info on skin effect, coil/stator saturation and y windings where the esc will see a short, It's quite possibly something to do with this. I don't suppose a shorter pwm might help? or higher timing? Unless you have all that covered already.

Repairable esc's don't grow on trees, there must be a way to test the motor using an esc with a ton of amp headroom or find an esc manufacturer willing to send a few as test samples, yge comes to mind who might rise to the challenge (or send them the motor to test for you).

Good luck as they say, it is a very interesting situation you have and one worth noting.

[Raptorapture]

You're kidding, right?

[HeliFX]

since scorpion motors have very little room under the stator holder.
there a good chance your exposed wire where its terminated is making contact with your holder hence causing a short.

did u check for short once motor was assembled ?

I've done tons of motors with every configuration and luckily never had esc burn or motor.
doing motor for other pilots has me extra,extra carefully.

don't think there anything wrong with your esc ...definitely would take a closer look at your motor rewinds.

I'd take it apart and do again and inspect the wire again

[omerco]

That comes to mind every time I terminate and assemble and here as well I checked it assembled and specifically verified there is no short under the stator. There is much room there by the way, more than I expected.

The final result would be to take it apart and rewind again, but since I can find nothing wrong with the motor now I can not be sure it would help, at least not with the same setup.

And finally a good word for scorpion: both ESC's are back with no charges! And the usual great service by Tony who even expediated the shipping for me.

[1BOHO]

At this gauge and rpm I doubt very seriously skin effect has anything to do with this. I'd think something simple like long motor screws. It isn't from pulling over 200 amps running normally. Think so? Testing with a forty dollar 200 amp mystery under load on a bench before marriage to the money seems logical if you have Pre esc jitters.....

Simply run suitable load on a bench for a duration as long as a flight. What other way can you observe what it will do under work.

Bad bearings and cold solder joints in the bullets on the motor or esc can cause issues. I use a big iron in a vice and hold the tinned terminal leads in a pool of molten silver solder in the bullet until the joint has fused then tug like hell.....

Best to not use them at all if possible....

Consider the cells as well.

[omerco]

Motor screws are far from the coils, and if they were not it would fail the 1000v test.
I have no way to bench run it at that load. Also I believe it will not simulate real life: the shorted stator motors tend to spike high amps on load buildup. The original 1.4 wire can spike more than 200a, and both my ESC's failed on high load spikes.

All that doesn't rule out that the problem is somewhere else, and it could be that the final solution will be a rewind. Problem is I can do all that and still burn another ESC...

Bearings are new.

[1BOHO]

.....Running a without a load will not tell u much in real life. 200 amp spikes ... That shouldn't burn a good esc with a solid supply in short duration under normal operation. I guess there are others ways to put motors through paces outside of the vehicles they drive. If you have rewound it twice already and believe in your megger rewinding it again doesn't seem like a feasible final solution.

[jamage]

I scrapped a bunch of motor cycle ignition stators last week. They were all burnt in the same place where the outgoing wires met the coil wires and only there on the local two coils to the sides, about 9 stators with same place burns. they all have 1.5mm ish windings.

[omerco]

I rewinded it only one time, and about other way to test out of the vehicle- I'm listening.

It could be the best would be to rewind it again, I'm gathering the energy to do so. Problem is if this really is a rewind problem - our tests on a completed motor have less integrity than I thought.

[powercroco]

if there weren't the custom - robber barons in between, I would say, send it to me.

what you can't find out on the mounted without scope motor is an short into one coil.
onthe other hand so the part motors must have different nspec....

if someone uses a high power laboratory powersupply with adjustable current nothing can happen to the esc.
high power means 10 or 15kW and 300 or 500Amps.
unfortunally someone could buy a littlke car for the price.

rewind it.
rewinding is maximum 2hours.
and testing it after this 15min......

[1BOHO]

Originally Posted by omerco

I rewinded it only one time, and about other way to test out of the vehicle- I'm listening.

It could be the best would be to rewind it again, I'm gathering the energy to do so. Problem is if this really is a rewind problem - our tests on a completed motor have less integrity than I thought.

I don't have a clue outside of a test bench or dyno that provides some type of load your real world way? If both halves have been wound for different n spec the esc wouldn't like that too much I imagine. No problems I see . You just can't rely solely on a megger which doesn't know whether u winded both halves the same or not. A resistance check on both halves should indicate a difference in resistance if there is less or more wire on one of the motors. The other way is to verify the kv of both halves before paralleling.An eazy check with a tach. A few sealed lithium automotive batteries in series could provide stable power to multiples of 12 volts and very high amp discharge ability .

[omerco]

Originally Posted by powercroco

if there weren't the custom - robber barons in between, I would say, send it to me.

what you can't find out on the mounted without scope motor is an short into one coil.
onthe other hand so the part motors must have different nspec....

if someone uses a high power laboratory powersupply with adjustable current nothing can happen to the esc.
high power means 10 or 15kW and 300 or 500Amps.
unfortunally someone could buy a littlke car for the price.

rewind it.
rewinding is maximum 2hours.
and testing it after this 15min......

I'm so stupid - I'm in Frankfurt...
Should have thought of it. I will see when I'm back maybe we will do that.

I was looking for shorted coil by measuring the resistance of each separate phases on the 2 different motors and all 6 were the same, but this is not a 1000v test.

And last - n spec is as expected.

(Rewinding it took me 2 weeks with the lack of time and practice I have right now )

[omerco]

OK - since this thread is close to dead, I'll put an update on my problems:

I have a new friend - the manager of a transformer factory in the south of the city. Last time I was there to get some new 1.5 mm wire for the rewind he also showed me his meggers collection: from 500 - 4000V

so I took the motor to him for testing: 1000V tested OK. 1500V buzzed lightly, then half motor shorted completely at 2000V and now it buzzes at 500V as well. the other half looks fine except for light hisses at 2000V.

Back at home I have decided to check my megger (Ebay's VC60B+) as well: connected it to my multimeter shows 480V instead of 1000V , But I'm unsure if this test is not averaged. maybe a scope is needed for that.

Rewind on the way.

[omerco]

I had another very old Scorpion 4525 lying around which I was given last year and burned shortly after I received it.

A simple calculation showed that if I'm using my last rewinded 1.5MM 4525 5+6T with 545KV and pinion 11, Than I can go with 10T and pinion 10 to get the exact same gearing - only with 1.6mm.

Even better - I went for the slightly lower KV/Higher torque variation of 4+6 (instead of 5+5) to get even better gearing.

This is the first motor I'm using the Dupont Nomex-Milar insulation paper from "Brocot" and it made the work completely different than the crappy Ebay paper. All Thanks to Dekker

so:

original scorpion::
KV: 545 rpm/V (YGE)
Wire: 5+6 YY 1.4mm.
Copper surface: 16.94mm^2
R= 12 mOhm

After:
4+6T YY 1.6mm

Motor 1: 585 rpm/V
Motor 2: 584 rpm/V
Together: 587 rpm/V (YGE, Timing 18)

Io: 4A@43.3V
R: 7.4 mOhm

Copper surface: 20.10 mm^2 (+18.7%)





Note: Finished with 3 layers of de-electical varnish.

Edit: Castle flight log uploaded

[1BOHO]

I've been looking at traditional transparent/translucent encapsulation materials and their thermal conductivity numbers and have discovered they aren't nearly as good as opaque ones that actually contain thermally conductive materials.

Here are a few photos and a great reading about this subject from Jim Hendershot's (An IEEE fellow) site.

http://motorsolver.com/mfg-services/...encapsulation/

Id like to try a fluid bath of epoxy powder on a scorpion stator for a paperless slot leaving more room for copper.

[omerco]

Wrong thread, I think. There was another one discussing insulation paper

[1BOHO]

No, I intentionally posted here. Since better paper and varnish was spoken of here, pointing out to the op and others interested that there are better ways to insulate raw stators and securing the windings may be useful. It was for me. I went through the trouble of making sure a motor was well encapsulated with multiple layers only to find out from professional builders that it only makes the material a better insulator.

V



So now I'm much less liberal with the transparent stuff if it is my only option. I also thin it with acetone let it flash off then cure it in an oven. Much less material for the wires to try to breath through and better capillary action to get in between the windings.

V

[Raptorapture]

Very nice!