Motor Troubleshooting

[jerjwillelec]

I don't get as much motor troubleshooting as I would like so I need a little help from you guys... I have a 10 HP 240 Volt 1 Phase Baldor Motor on an Airstream grain bin dryer. As soon as I hit the start button, the (SQD 8910 DPA 63) contactor makes and the breaker trips. Almost like there is a dead short somewhere but no "explosion" to go with it. I replaced a burnt capacitor due to a loose connector but I'm thinking the two are unrealated. Any thoughts?

 

[kwired]

Meg motor windings to ground. Make sure low reading is in winding and not in capacitor or starting switch. If windings have low reading motor is toast.

If insulation test is a pass maybe you have a bad breaker.

 

[jcole]

Can you disconnect motor from mechanical load and start it safely? Maybe you have a locked rotor conditon.

There are four things that can be wrong IMO. I assume not a new install.

1. Mechanical overload.
2. Internal motor short
3. Branch circuit short.
4. Bad breaker

 

[RichB]

While you have the motor leads disconnected for meggering, safe off the T-leads and try the starter--if it works then a motor problem--if it still trips thwen a breaker or conductor problem.--Isolate, adapt and overcome--to paraphrase!

 

[jerjwillelec]

Thanks all... After reading your comments, it appears I had really done more than I thought. The breaker holds until I push start so it isn't a branch circuit or conductor issue. I swapped out the breaker with another and get the same results so I'll write off the breaker. Checking out the motor next.