Help with electric motor fault diagnosis? :¬(

[guineafowl21]

Have you tried plugging it into the other radial circuit? Just in case that awful RCBO has failed - an unlikely coincidence, but easy to check. Edit: crossed with porker!

Re-check the new wiring?

Does the motor shaft spin freely by hand?

Can you blow out the motor with compressed air?

I guess the motor is a resistance start type, since there’s no cap. But there’s still normally a centrifugal switch that could be stuck. If the above doesn’t work it may be time to open up the motor. I can’t see paint dust causing a short without some interesting fireworks, but if there’s metal dust...

 

[peter-harrison]

So doesn't the motor have a capacitor?
Because it sounds pretty much how my extractor carries on when it has burnt out yet another one.

 

[Myfordman]

This is only a very low power motor and does not need a capacitor.
250 watts

 

[Deadeye]

Hi folks
I'm away for the weekend... But will follow those tips on return and report back.
It's tripped both the consumer unit where it started and the one in the cellar when I brought it in there so I don't think it's the breaker. I'll test from plug on Sunday night

 

[Deadeye]

I'll give it another blow as well. Possible some metal dust from sanding I guess. Pulley turns perfectly

 

[Sideways]

This is an old and not very high power motor. Even though AC motors like this can draw 5x to 7x their designed current while starting, I'd expect a 20A breaker to cope.
Miniature circuit breakers are more sensitive than fuses of the same rating, so just in case I'm wrong, try plugging it into the ring main circuit as that has a 30A breaker. Connect it using a 13A plug, A 13A fuse will carry rather more than 20A for long enough to give the motor time to start if it's going to. Turn it off after 5 sec if it doesn't start. As I don't know the sizes of your wires, this is a diagnostic test, not a way to operate it regularly.

The problem indirectly reminds me of something obscure.
A couple of years ago I rerurbished an old Delta brand USA but 240V belt disc sander. In the process I was introduced to an old method of motor starting I'd never seen or been taught about. It had an additional coil in the motor to help with starting, not so unusual but this was especially low resistance and drew a big current surge just for moments during starting. The high current also passed through an electromagnet coil. This pulled a switch contact up against the force of gravity to keep the starting circuit powered up while the motor accelerated. As the motor reached speed (in just a second), the surge current reduced, the force of the electromagnet dropped too until it was no longer able to overpower the force of gravity acting inside the switch. The switch opened and disconnected the starting circuit.

If - just if - your motor includes something old and unusual, it might not work properly lying on it's side on the bench. In my example, gravity switches need to be in an upright position or they don't work.
Try refitting the motor to the drill and even reattach the belt so that the motor is being operated the way it was intended just to eliminate the 1% chance that this matters.
I'd agree with everything myfordman has advised...

 

[Deadeye]

Well, it's working - that's the good news.
The bad news is I don't really know why.
I went to do the multimeter tests again and found the battery had failed. I replaced the battery... and got different readings. Then I tried turning the shaft and found that the readings varied. I borrowed a better meter and got more, different numbers. By now I was ready to take the cover off and hit the thing with a hammer.
But I thought I'd have one last go at shifting any short. So I rigged up somthing to turn the shaft while I put the vent end of the motor against a 4" inlet to my dust extractor and blew compressed air in the other end. Ran it for a few minutes and when I plugged in - starts and runs.

I have learned two valuable lessons:
1. The point about not messing about with things just to prettify them is well made (although it stung a bit at the time). Especially when you know nothing about electrics.
2. The patience and kindness of people on this forum is amazing. Thank you! I will strive to return the favour (although it's doubtful you'll need to know much virology)

 

[Myfordman]

Well, it's working - that's the good news.
The bad news is I don't really know why.
I went to do the multimeter tests again and found the battery had failed. I replaced the battery... and got different readings. Then I tried turning the shaft and found that the readings varied. I borrowed a better meter and got more, different numbers. By now I was ready to take the cover off and hit the thing with a hammer.
But I thought I'd have one last go at shifting any short. So I rigged up somthing to turn the shaft while I put the vent end of the motor against a 4" inlet to my dust extractor and blew compressed air in the other end. Ran it for a few minutes and when I plugged in - starts and runs.

I have learned two valuable lessons:
1. The point about not messing about with things just to prettify them is well made (although it stung a bit at the time). Especially when you know nothing about electrics.
2. The patience and kindness of people on this forum is amazing. Thank you! I will strive to return the favour (although it's doubtful you'll need to know much virology)

Oops! it was not meant to sting that much! But good news it is all running now!

 

[Deadeye]

Hey! No worries - it was entirely fair and I'm *so* grateful for the advice and support.

 

[guineafowl21]

Glad you got it sorted. Get yourself a decent meter - you’ll find all sorts of uses for it if you’re practical, and they’re reliable, accurate and safe. Troubleshooting is hard enough without having to second-guess your equipment.

I like my Fluke 87V, but there are lower-end models available. You pay a little more for the name but it’s a meter for life.

 

[Vann]

...I will strive to return the favour (although it's doubtful you'll need to know much virology)

Huh. You spoke too soon...

Cheers, Vann.