split phase motor issues

jmm03 · Mar 24, 2019

Hello all, 1/4 hp carbonator type motor on a TIG cooler won't start intermittently. Might work 50 times in succession, not on the 51st. might work 3 times not start the fourth. Well oiled, centrifugal switch has no issues that I can see, it does not appear to occur in the same place on the armature when it comes to a stop, if I turn the armature slightly sometimes it will start sometimes it won't and I have to turn it more then it will. There is a new motor being purchased in the interest of reliability,but I sure hate not being able to figure it out and would appreciate any thoughts or suggestions. Thanks, Jim

Froneck · Mar 25, 2019

I assume that you saying it's split phase you do not have a capacitor. You say the centrifugal switch works fine but is it making contact? Often wiring is needed to determine rotation, are the start winding connections good or could they be loose and arcing?

Jraef · Mar 25, 2019

If it can start after moving it, I would suspect that one of the rotor bars has a break somewhere, usually at the end ring. Not really worth fixing on something that small.

hermetic · Mar 25, 2019

try cleaning the contacts on the centrifugal switch, sound like they may be closed, but not making contact electrically, common problem.

TDegenhart · Mar 25, 2019

From the description, I am not sure if he has a universal or capacitor start motor.

Tom

jmm03 · Mar 25, 2019

Hello all, I have not opened it up to delve into its guts, I suspect something open, but as was said above it is not really economical to fix if it is a break somewhere.(which I really hate, but what do you do?) It must be considered a universal since there are no caps, it is an Emerson S55NXNSM-7296, no bearings,just oil type bushings that I had hoped were the issue but weren't,once I get it apart i'll check the centrifugal switch and look for any obvious signs of opens . Appreciate the feedback so far. Thanks, Jim P.S., jraef, is that a picture of Nikola as a young man?

SAF · Mar 25, 2019

Typical carbonator pump is split phase with no cap.
Could also be a problem with the overload protector snap disc control.

SAF Ω

Froneck · Mar 26, 2019

I seen in the photo it states Non-Reversible, are you sure it Split phase? It could be shaded pole. Are you sure it has a centrifugal switch?

jmm03 · Mar 26, 2019

pictures are not of the motor I have. since it says "split phase" on the nameplate and does not have a cap housing and I can hear the centrifugal switch releasing, I am reasonably sure that it is what it says...

TDegenhart · Mar 26, 2019

The type you refer to is called a split phase motor. It uses the resistance of the start winding to shift the phase enough to get the motor started. These have very little starting torque. The most likely problem is the starting switch followed by a break in the start winding.

Tom

Jraef · Mar 26, 2019

If it were a break in the starting winding or the centrifugal switch not closing, moving it slightly would not overcome the inability to start. That's why I was thinking a broken rotor bar, because if it stops where the bad bar happens to line up with the initial pole that gets energized first, it fails to develop enough torque to move the rotor. Rotating it by hand moves it enough to get it to a better spot so it can generate more torque.

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