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micro mill electricals problems, help please!!

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pmdevlin:
Hi Dave,

I ran the motor on 12v some time ago, it wasn't quite enough to spin the shaft. When I collected it from the tester guy, he had it running fine on 60vdc to prove to me the ac input had not ended the motor. Maybe now it was back on 230vdc, it was just too much. What a dilemma.

I was tempted to get my lathe out and start swopping bits over, such as motor,  but I really don't want to end up with two dead machines, its just not worth the risk as I don't know the original cause.

Paul

steampunkpete:

--- Quote ---Stuart, I paid no attention to that, however might be lucky. With the two studs that go from top to bottom inside the can, you can only assemble in one of two ways, so the end could be 180 degrees out. I would have thought that didn't matter? as the brushes are infact in the same place, or does it as one will be positive and one negative connection?
--- End quote ---

If you assembled it with the brushes 180 degrees out the motor would run backwards because the field from the PM and the armature would be reversed relative to each other. If you look up "Fleming's Left Hand Rule" in Google / Wikipedia all will be explained (it's a way of remembering how the field and current interact to create movement using the thumb and first two fingers of the left hand).

lordedmond:
Pete

Ye gods it was eons ago when I was taught the Flemings rules

Paul

Yes I agree the studs we go though but the brush setting has to be accurate to one com seg

Now this will sound odd in what has been said about DC motors and AC one the big stuff 75 hp up we used a 1 kW heating element and applied the AC to the field coils with the com coils disconnected with a volt meter across the brush gear we set them for a null

As Dave has said the motors can seem to be to be ok but fail when fed with the pulsed DC from the controller we tend to test with a steady DC source when we should be testing in normal operating conditions, which is the practice that I have normally used at work , strictly against H&S as I normaly tested with the circuit live .
Along with dave I have lost a motor on a x3 mill tested fine but released magic smoke and sparked . Not worth my time to rewind it which I could so got a new one and enjoyed using it to make my models
Just my 2cents on the matter
Stuart

steampunkpete:

--- Quote ---Ye gods it was eons ago when I was taught the Flemings rules
--- End quote ---

Yes, about 45 years in my case.

On the whole it does look like the motor is faulty - assuming that the rest of the circuitry has been inspected for poor connections, frayed / chaffed wiring, dry joints etc. So it looks like a new one or a re-wind. Has anybody any experience of getting motors rewound and what is costs? I can't imagine it's cheaper than a new motor in this price range.

You may have seen my post on the acquisition of a virtually new Clarke mini-lathe for spares, only to find its odd and erratic behaviour wasn't down to a duff control board, but caused by a dodgy connection in the wiring, so it might be worth a last double check prior to splashing out on a new motor. If you have an emergency stop button like those on the mini-lathes, it is worth paying attention to the soundness of the spade connections to the emergency stop button and checking that the contacts don't rub on the insulating covers of the spade connectors.

lordedmond:
Only 45 years you young pup

Let's see it would be about 1963 so that's about 52 years ago


As to a rewind it should not be to bad if you are set up for stoving and balancing be a six hour job so not worth it hek I did not do my own not cost effective

Regards Stuart

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