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Old Jun 22, 2012, 07:21 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,872 Posts
Help!
Why does this motor run then stop?

Wonder if any of the motor gurus can advise on a problem.

I went to set up small power system for a club mate who has a park size Tiger Moth.

I had a nice little new motor in the bits box that I got a few years ago - sold by HK and got a good rap from Dr Kiwi and Bruce Abbott.

It's this one, the D2211-1700, made by Shenzhen Linchaoda Electronic Co., Ltd.

Data here: http://www.peakeff.com/beta/MotorDet...x?MotorID=3862

It stutters but will start eventually and run quite smoothly on a Turnigy (Hobbywing) 6A ESC. Stops when current exceeds 3.9A or left to run at just under 3.8A for more than 20 secs.
Stutters and will not run on any of the 3 timings on a Turnigy (Hobbywing) 10A ESC.
Stutters and will not run on any of the 3 timings on a Turnigy Plush (Hobbywing) 18A ESC.

All on an APC 7x4, and a freshly charged 2S 2200 mAH battery so is not a low voltage issue (voltage measured to be just on 4V/cell when motor stops).

Resistance between wires is:
980.7 mOhm
469.4 mOhm
512.4 mOhm

Given that the quoted/measured Rm is 0.47-0.51 Ohms I infer from this that one winding is shorted out.

So the questions are:

1) Why does it run at all, then stop at a certain current/speed? Is it because the feedback from the back EMF gets out of step and confuses the micro processor?
2) Is it worth trying to repair. I won't rewind it but could have a go at a broken exit wire. What are people's experience with this kind of fault?

To put it in context, a new one is $10 from HobbyKing.

Thanks for any advice.

John
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Old Jun 23, 2012, 12:03 AM
Dude, I do fly all day long!
rcalldaylong's Avatar
San Jose, California
Joined Dec 2007
5,864 Posts
Quote:
Originally Posted by jj604 View Post
So the questions are:

1) Why does it run at all, then stop at a certain current/speed? Is it because the feedback from the back EMF gets out of step and confuses the micro processor?
2) Is it worth trying to repair. I won't rewind it but could have a go at a broken exit wire. What are people's experience with this kind of fault?

To put it in context, a new one is $10 from HobbyKing.

Thanks for any advice.

John
I couldn't tell you technically why it runs when there's an obvious short...other than that I've run into plenty where it does run, but ESC is hot. I'll let the tech gurus answer that one.

That being said, my advice is that this motor is worth the rewind. I've rewound this motor before. The windings aren't soaked in expoxy, and it's a bell type (don't have to take the stator off), making it a very simple. You could probably get the motor apart, with all the windings off in less than 15 mins...then rewind it in less than 30. In under 1 hr you could have a better motor than a brand new one.
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Old Jun 23, 2012, 01:01 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,872 Posts
Thanks, that's very helpful.

I might make this my first rewind!

Any suggestions on wire gauge? I am assuming once you have chosen the gauge you just fill up the stator slots evenly and as much as possible with equal turns. Are these motors delta or wye wound?

I can simply copy what they have done as I unwind it I guess.

John

Quote:
Originally Posted by rcalldaylong View Post
I couldn't tell you technically why it runs when there's an obvious short...other than that I've run into plenty where it does run, but ESC is hot. I'll let the tech gurus answer that one.

That being said, my advice is that this motor is worth the rewind. I've rewound this motor before. The windings aren't soaked in expoxy, and it's a bell type (don't have to take the stator off), making it a very simple. You could probably get the motor apart, with all the windings off in less than 15 mins...then rewind it in less than 30. In under 1 hr you could have a better motor than a brand new one.
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Old Jun 23, 2012, 01:07 AM
Dude, I do fly all day long!
rcalldaylong's Avatar
San Jose, California
Joined Dec 2007
5,864 Posts
Quote:
Originally Posted by jj604 View Post
Thanks, that's very helpful.

I might make this my first rewind!

Any suggestions on wire gauge? I am assuming once you have chosen the gauge you just fill up the stator slots evenly and as much as possible with equal turns. Are these motors delta or wye wound?

I can simply copy what they have done as I unwind it I guess.

John
You can't go wrong, this motor would make a good first wind.

can't remember what awg I used for mine...it's been so long ago, but my rewind was purposely for a high kv micro jet, so awg was quite big for a little motor. Just measure the stock, and count number of turns.

if you want ~kv, then use the same awg to get close to the same number of winds, if you want higher kv, user bigger awg, lower kv, smaller awg.

good luck!
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Old Jun 23, 2012, 02:53 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,872 Posts
Thanks, sounds straightforward.

Quote:
Originally Posted by rcalldaylong View Post
You can't go wrong, this motor would make a good first wind.

can't remember what awg I used for mine...it's been so long ago, but my rewind was purposely for a high kv micro jet, so awg was quite big for a little motor. Just measure the stock, and count number of turns.

if you want ~kv, then use the same awg to get close to the same number of winds, if you want higher kv, user bigger awg, lower kv, smaller awg.

good luck!
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Old Jun 23, 2012, 10:33 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,218 Posts
Quote:
Originally Posted by jj604 View Post
Thanks, that's very helpful.

I might make this my first rewind!

Any suggestions on wire gauge? I am assuming once you have chosen the gauge you just fill up the stator slots evenly and as much as possible with equal turns. Are these motors delta or wye wound?

I can simply copy what they have done as I unwind it I guess.

John
I can't tell for sure by the photo (and that might not be right anyway) but if your motor is wound with a single strand you can just match that wire size. If it has multiple strands in parallel (done to make it effectively one larger strand) you can use a single strand that has the same (or, if possible, more) surface area of the multiple strands.

The most commonly found wire on multiple strand winds is about 0.25mm in diameter (includes the coating). You can look up wire that size on the wiki AWG page and get the surface area. 31 AWG or 0.227 mm wire is the closest size, that wire has an area of 0.0404 mm2 and two strands would be 0.0808 mm2. Looking up the table at the larger wires, 28 AWG wire (0.081 mm2) or larger would be the candidate sizes.

When you strip your motor, count the turns. If it is a single strand wind use the wire you took off and put the same number of turns on one arm but arrange them neatly side by size. Go from the inner end of a arm to the outer end and make the second layer on top of the first. You can even add a turn or two in a third layer if you need to do that to get all the turns on.

Do the same thing on an adjacent arm to check the fit of the wire.

If you have room left (clearance between two arms basically) when you get the turns on the second arm you can use a slightly larger wire (27 or 26 AWG maybe). As the wire size is increased the current carrying capacity of the windings will increase. That will increase the power and your neatly arranged side by side windings will make for a smoother and better running motor too.

You motor looks like it has 9 stator arms and 12 magnets (also called a 9N12P motor, N = Nuten or stator arms and P = Poles or magnets). So it will most likely be wound in a method called ABCABCABC. You can check that as you unwind it. If it is a ABC wind the three phases will be wound with a wire (or bundle of of small wires) starting on 3 arms in sequence and then skipping two arms as it goes to the 2nd and 3rd arms. So phase A will be on arms 1-4-7, phase B will be on 2-5-8, and phase C will be on 3-6-9.

This manual will show you how to wind a ABC wind on a 9 arm stator. And you want to terminate in the Delta method as shown there if that was how your motor is terminated now.

http://www.micronradiocontrol.co.uk/.../KH-278-v2.pdf

The Star termination, if that was used, would have a small bundle of three wire ends soldered together, insulated, and just laying somewhere on the back of the windings.

In either case, you want to use the same termination.

Jack
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Old Jun 23, 2012, 07:47 PM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,872 Posts
Thanks for that comprehensive explanation, Jack. Much appreciate the effort you went to. I also spotted the "Motor Troubles" thread you had responded to and had a look at the winding manual on the Micron thread. Very helpful in understanding how to do it.

Oh dear, this looks like another possibly addictive, never ending pastime.

John
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Old Jun 23, 2012, 07:58 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,218 Posts
You're more than welcome. It only took me one rewind to get thoroughly addicted to messing with the motors. It is just another entertaining and rewarding aspect of the hobby.

I think I am a mediocre pilot for the most part and enjoy the building and messing with the power systems almost as much as the flying...

Good luck with it!

Jack
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