Drum sander motor-Diagnose bad run cap???

[John C Bush]

My Performax 25" drum sander drum motor has begun to shut down in the midst of modest stock sanding. It has a 1.75hp 120vac motor with the SmartSand amp control system and the motor never feels hot, so unlikely its an overload issue. After 5-10 min. of sitting idle it fires back up. There are two capacitor covers and I have yet to investigate to see which one may be the run or start cap. Beyond a leaky cap how else do I determine which is which and if one is toast. Don't have a manual to review and I know the SCM wisdom pool will have an answer. Thanks, John

[Rod Sheridan]

The run capacitor will be small, maybe 20 to 40 uF.

The start capacitor will be large, maybe 200 to 300 uF. The start cap would not cause the motor to overheat.

Have you measured the motor current?

Regards, Rod

[Richard Coers]

Does it have a centrifugal start switch? If that is staying engaged, it can give some issues with running.

[John C Bush]

Thanks Rod:
Haven't measured motor current--How would I do that? The SandSmart controls feed belt speed so I assumed that "controls" motor amp load. Is that what you are referring to?

Thanks Richard:
The motor will start and run just fine for a while then just shut down with no apparent overload. No slowdown when sanding and it has stopped a couple of times with no stock in the sander at all.

I will uncover the caps and see if there is a visual indication of failure. Not sure how else to test.

Thanks guys. JCB

[Mikail Khan]

70% of the capacitors I have replaced have shown visual damage. A capacitance tester can be purchased on Amazon for less than $20.

MK

[Jeff Bartley]

Thanks Rod:
Haven't measured motor current--How would I do that? The SandSmart controls feed belt speed so I assumed that "controls" motor amp load. Is that what you are referring to?

Thanks Richard:
The motor will start and run just fine for a while then just shut down with no apparent overload. No slowdown when sanding and it has stopped a couple of times with no stock in the sander at all.

I will uncover the caps and see if there is a visual indication of failure. Not sure how else to test.

Thanks guys. JCB

For under $20 you can buy a clamp on amp meter to measure the load. Good tool to have.

[Bill Dufour]

To use. aclamp on meter you have to make a short cheater cord. It ha sto break out each conductor separately so they can be clamped individually. If you clamp a regular power cord it will read zero amps. This is because half the time the amps flow one way half the time the other way. So on average there is no net flow. Kind of like waves on a beach. They do not actually add water with each wave.
Dc will read the same way on combined in and out flow being equal.
Bill D.