Weird issue I’m having - 3ph motor.

[Brian Holcombe]

I went to use the Omga today, turn on the rotary, fire the switch ‘buzzing sound’. So I checked the leads to the motor, everything is tight. Tried two other motors against the converter and they run fine.

Next I checked the capacitors in the rotary phase converter, they measure within a few % of the rated capacitance.

Then I checked the motor on the Omga, checked each winding, all test within a very narrow range, no shorts between windings and no short to the motor case that I can find (I tested with meter but not a megohm meter.)

Next I turn the motor by hand, spins easily.

I haven’t yet tried to start it with the belt removed but just will be next.

This setup ran yesterday and has been running fine for a few weeks but I have not put a lot of hours on it (just fixing it up and setting it up)

Running out of things to check on this setup and I’ve yet to see a standout issue. The switch seems ok since the motor is buzzing but I haven’t checked voltage there yet.

I did check voltage at the switch, 115v/lead except the rotary which is idling at 235v

[Ron Selzer]

"fire the switch ‘buzzing sound’."

that typically is a contactor not pulling in tight, pull the coil out and clean any rust, dirt, etc off of it and then try it. Might end up having to change transformer leads in switch to a different set of incoming wires as it may not like the made up third leg. I have no experience with phase converters, fair amount with 3 phase motors and controls.
Ron

[Brian Holcombe]

Solved, and I’m wearing the dunce cap today. The switching all felt tight and clean so my mind immediately went to bigger issues. Turns out the switch was bad.

This machine uses an arming switch and then a simple 3-pole switch to turn on the motor, one lead wasn’t making contact.

[Bill Dufour]

I think they call that "single phasing". I belive the motor will continue running at reduced horsepower but double the amps and extra vibration but, it will not start from non rotating.
Bil lD.

[Brian Holcombe]

Bill, It wouldn't start even with me rotating it. One of the reasons I initially thought it was something else and not just a dropped lead.

When the switch died, it didn't stop functioning completely, instead just one of the leads dropped.

[Bill Dufour]

I think it has to get up to 2/3 rpm or close to run at all. I meant it would keep spinning at reduced rpm if it failed while it was running. I hope to never find out. Thanks for the warning.
Bil lD