Dead AC Motor?

TheArsonSmith

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While trying to adjust the level of my lathe in this video:


The motor stopped on me and just started humming. You can see in the video I pulled it and put it on the bench, replaced the start cap with another dissimilar one (I also ordered an exact replacement and tried with that one to no avail) it did the same thing just a hum and even manually trying to start it it wouldn't turn.

I'm guessing the run coil is burned out but a full disassembly didn't reveal anything burnt or obviously broken.

Before I throw the old motor out is there anything I should double check that may breath life back into this guy?

Thanks,
- TheArsonSmith (Bill)
 
Aside from the motor problem, if you are trying to level your lathe using the two collar method, You don';t want to use the tailstock center. The bar must be free on the far end.
 
I kinda thought about that, but I should be able to get it started by hand still right?

While it was apart I also did flip it backand forth by hand a few times and it seemed to move freely.

This was the first time I've ever had an AC motor like this apart past the startup capacitor though so I really didn't know exactly what to look for.
 
I think your assessment of a run winding going south is likely correct. but check the centrifugal switch anyway. It takes a bit of speed before the run winding is capable of overcoming the load.
I would check for continuity on the run winding. If there is continuity, most likely a shorted winding. If the winding is open check fo ra bad connection. With the capacitor removed, do you still get a hum? If not, another indicator for an open run winding.
 
Hello Bill,

After watching your video about the motor on your lathe ! The fact that the motor hums and the rotor remains stationary, suggests that the start windings are OK. You really need a multimeter on the ohms range to check the run winding resistance, and see if it has gone open. Did you check to see if the bearings were OK ? Because bearing failure can allow the rotor to touch the stator and you will get the noise, the buzz you heard.

Anyway nice new replacement motor.
 
I'll pull it aprt and try checking the resistance across the coils when I get home tonight.
 
The motor stopped on me and just started humming.
I'm guessing the run coil is burned out but a full disassembly didn't reveal anything burnt or obviously broken.

There may be a thermal cutout wired into the motor, and those are often replaceable. Otherwise, look at mechanical
connections of the internal wiring (the run wiring goes to a terminal, it could be just a loose nut or bad crimp).
 
Hi Guys,

A motor of that size doesn't usually have a thermal cutout embedded, if they do have one, it is often a resetable one with a red button visible from the outside. In any case it would cut power to the whole motor, not just the run winding, so if that were the case there would not be any hum.

I do agree that loose wiring, or bad crimp, even a break in a wire could cause the motor failure in the way it did. My best guess would be bearing failure since there seems to be no sign of overheating, particularly because of the difficulty in rotating the motor shaft when power is applied.
 
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