Motor Issue

Theanswers

Hello,

I have an old Brooks Compton Motor in my lathe. It was running in forward rotation and accidental I hit the reverse switch. There was a loud bang (Electrical) and then the lathe stopped. I checked the fuse it's fine, Manual pressed in the contactor. Still nothing. Then checked was power getting to the motor and yes.

Would it be the Capacitors that have gone faulty?
How would one know?

Thanks
Peter

Bruthal

There may be an overload relay in the contactor setup. It would usually be below the contactor itself, with a reset button on it if fitted.

But if pushing in the contactor itself is not starting the motor, its probably not that.

How did you check power to the motor?

Is it a single phase lathe?

Theanswers

Bruthal wrote: »

There may be an overload relay in the contactor setup. It would usually be below the contactor itself, with a reset button on it if fitted.

But if pushing in the contactor itself is not starting the motor, its probably not that.

How did you check power to the motor?

Is it a single phase lathe?

I bypassed the contactor by manually bypassing the wiring so I would be able to check the power on the motor. Power was making it directly onto the terminals on the motor and no attempt to start was being made. The motor is 3 phase.

How would one test a capacitor?

frankmul

Three phase motor don't have capacitors, what makes you think there are capacitors there?

Theanswers

Sorry, It's that time of the day! It's single phase, don't know what I was thinking.

2 big capacitors on top. I assume a start and a run?

Bruthal

Some people would test for voltage with a phase tester, but that doesn't show both live and neutral present. I'll assume you used a volt meter onto both terminals anyway.

Did you try motor in both directions?

On that design there are probably 2 capacitors on the start winding, one is permenently in the start winding, the other switches out once motor is running. It would have switched into a reversing motor when the reverse was hit, possibly damaging it.

The capacitors are likely 2 different sizes such as 25uf and 250uf.
You can check capacitors with meter, easier with moving coil one but digital one should give indication.

Disconnect capacitor. Check for voltage first with meter in voltage setting.

Now put into ohms for resistance and connect to capacitor. Good capacitor will show a reading but quickly head to OL or open circuit display the same as when meter leads are connected to nothing.

Reverse leads onto capacitor and same should happen. A shorted capacitor will show 0 or low ohms reading. Open circuit capacitor will show nothing when leads connected to it.

The above tests are just an indication rather than proof, its a while since did any of them myself.