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Whats wrong with this motor?

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paulmorrishill

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Hi, I bought a mobility scooter off of ebay for £36, for a bicycle replacement vehicle. It worked great for a bit but while I was doing a range test to see if it was a worthwhile project, i neglected to monitor the motor temperature as riding at 15mph was too much fun. The motor lasted about 6 miles before it finally gave up and the enamel burnt off of the windings and caused a short. So I took the motor off disassembled it, and unwound the windings, stupidly I neglected to take any photos the only data I recorded were the number of turns and coil width, as well as the wire thickness.
Luckily I had a smaller 100w dc motor available that I could have a look at for an idea of what it should look like. I wound the motor according the the layout of the smaller one with brand new wire, unfortunately the motor does not perform as it should. It starts alot slower than it should taking about 1 - 2 second to reach its maximum rpm. Not only that but no load conditions it draws 6 amps which is a bit ridiculous. After running for about a minute the brushes have increased in temperature by about 60 degrees. I have checked for shorts between the coils and the armature there are none, nor are there shorts between the commutator plate things.

I am utterly stuck

After searching the internet for hours I found a website with a wiring diagram for an electric scooter motor that shows exactly how I have wound this motor. I can provide photos if it would be of any extra help in diagnosing.

This motor is about 800-1000w (based on dimensions of similarly constructed motors (the label was worn away))

I don't want to replace the motor because it would be very expensive, around £80, well for me at least. Not to mention trying to get the motor to connect to the current gearing for the mobility scooter.

Thanks in advance for any help, I am on the point of scrapping it or waiting for a new mobility scooter to come up on Ebay.


Paul
 

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So correct me if I am wrong but you rewound the rotor?
It would be nice to post the same pic but with the stator
magnets. Of course we should know how many poles it has.
It should be two but you newer know.
 
I'm impressed. Doing winding for such an armature is very arduous. Did you take note on the SWG of the wire? That can be very critical for the performance. If you rewound the whole thing using thicker wires, I think I'll draw more current since the armature resistance is low, and vice versa.
 
That was a mammoth project, I can remind you is, not to break the paint of magnet wire.
 
Ye wire thickness is the same. I'm starting to think it may have something to do with the stator poles. Each pole has 3 magnet sections i had to take these out to get off some iron filings that were stuck to them, I think in the process of putting then back into the casing I mixed the up or something because I can see no other way this motor wont work.
 
that'll be it... but you'll have to unwind it (most frustrating part, been there done that) and replace the iron cores. That's the part where the magnetic flux is concentrated for efficiency.
 
I have solved the problem. The issue was with the two poles. Each pole was made with 3 magnets, and there were two different types of magnet. Basically I had a pole in the motor that was NSN and a pole that was SNS (s and n representing north and south) as opposed to NNN and SSS. So the motor was struggling against itself.
 
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