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Re-winding a PMDC motor? Answered

I have a 12V 5000RPM 15A PMDC motor and even at its top speed I can stop it by hand which is just not right. I took the armature out and here is what I found: Its a 2pole with 16 winding slots, each winding is quite large but theirs only 3 wraps! I know if you half the wire surface area and double the wraps you get half the RPM. Currently the rotor has 3 wraps per coil of 18guage wire with easily enough room for 10x that. What wire size and how many wraps should I re-wind this motor to get maximum torque at 2000RPM?


I'm not convinced you're driving 15A through this if you can stop it by hand - what are you powering this with? L

I just tuned the brush position last night to get the lowest no load current (should be the neutral position) and here are my readings:

Source: 15.5V (375VA xformer from a battery charger)
No load Current: 3.7A
No Load Speed: 5120rpm
Stall Current: 10.1A
Stall Voltage: 14.85V

If you do 15.5v * 10.1A / 12V = 13A so it is running pretty close to 15A I have my DMM in series with the motor and its input can handle 25A and I have run another motor at 22A with this same xformer.

You can stall it by hand with 15A going through it? A gearbox / some gearing is an alternative. More wraps would mean less current. L

I currently have it on a 3:1 belt drive which makes it bearable to use but if I can get better torque with a different winding and pulley combo it would be better. I am hoping this will replace my 1/4HP single phase AC 1725rpm motor as its to expensive to control its speed. What is the ratio between speed, # of windings, and wire size? I know wraps:speed in inversely proportional but what about wire size? Would I be right in saying if you double the wraps and double the gauge shouldn't you still have the same speed? Original is 19gauge, 3wraps, 5000rpm so I could use 16gauge, 8wraps, and get ~1800rpm.

What you say sounds about right, but it's that long since I rewound a motor I can't remember. You'll have seen this page?
Best wishes for it anyway.


Thanks for the link, a good read. He mentions a calculator to help choose the size of magnet wire but I dont see one anywhere. Do you know of the one he's talking about?

My eyes and my web-browser can't find the word "calculator" in the guide, but it is in a comment. So I can't answer that question. L

2nd paragraph: Included on this page is a small, easy to use program that will assist anyone interested in rewinding motors in choosing the proper "Magnet Wire" for their particular motor. The program is offered free from the manufacturer and is included here as a small download so as to eliminate the necessity of serious web browsing in order to find this information. unfortunately he didn't mention who the manufacturer was and all night on google turned up nothing, I cant even find many magnet wire mfg's even