When an AC motor overheats badly, what is generally the first point or two that it will fail at? And what will be required to remedy the problem?(I see alot of carbonization of the coils in various places.)'m working on bringing an old single phase 120 V, 12 A motor back into operation but I'm a bit new to motor theory and many other things under the sun.I pulled the motor off the table saw it came from, cleaned it up, realigned the extremely misaligned rotor with the stator so it turns easily again BUT it still isn't working, it just sits there and hums it's terrible hum. So obviously the alignment is not the current cause of the motors inability to operate.Thanks for your help!
By the sound of things (The Humming noise) your rotor windings have a short circuit. They can be tested on a machine that is an electro magnet. Most auto electricians should have one. (Especially the old guys). I can remember the name of the machine sorry. Takes all of 2 minutes.
There are many case for non operation of ac machine.This trouble shoot will help to find the answer 1.Find the air circulation holes block age 2.Find the carbon brush position and condition. The second point may be the Solution for your problem
You could have a phase to ground fault that prevents the motor from starting, which means a rewind or trashing the whole thing, But the most likely thing (at least the one to check first) is your starting capacitor. If that is bad, then current can run through the windings but there will not be a lagging magnetic field in the rotor that the winding magnetic field can push against.
First of all, what sort of motor is it? There are several that will usually be found running from single phase AC. Heres how you can identify them: If there are brushes/commutator then it is a series wound DC motor (a 'universal' motor, pretty common in lots of small appliances) If the rotor looks like a solid piece of metal, or perhaps appears to consist of only iron laminations, then it is an induction motor of some form: What does the stator look like? How many 'poles'? Does each pole appear to have a smaller pole near it, with a shorted copper strap around it If so it is a shaded pole motor or, how many electrical connections does the stator have, if there are two, it is probably a shaded pole motor An 'ordinary' single phase induction motor will have at least two (electrically) seperate windings on the stator, one of which will usually have a capacitor in series with it, or is switched on only to start the motor. So if there are capacitors or multiple connections, it is probably a regular induction machine. If the rotor is a permenant magnet it would be a synchronous machine (unlikely, would require a box of control electronics to run in anycase) Have a look at what sort of motor it is so we can help you more, Its probably a universal motor...
Partly shorted between some winding due to aging,especial after overheated. Redo the whole winding and drip it into high temperature Epoxy.
