Need help with electric motor

[Cogsy]

I was running my lathe today and switched into reverse for possibly the first time ever. It's just an electrical switch that reverses the motor, not a back-gear. The first couple of times I stopped and started the lathe was fine, but then the motor started slowly one time, with an audible hum. Sort of like it was having an issue with a start capacitor. After that it was fine, and I switched back to forwards.

A little while later (I was doing a lot of start-stop machining) it began having an issue when trying to start. Sometimes the motor just hums and doesn't turn - even when I flick the chuck (and a desk lamp on the same outlet dims), sometimes it turns slowly for a while then spins up to speed, and sometimes the push button just doesn't seem to 'engage' (it doesn;t turn at all when this happens).

The 'on' switch is a push button that makes a solid 'thunk' when it engages, and sometimes as the motor spins up I can hear the switch 'thunking' repeatedly. It's not a switch that stays pushed in when released, I think it's a magnetic type switch maybe?

Anyway, when it refuses to start altogether, I can generally bang it into reverse and it'll start first time, most times. So I'm wondering if the experts think I have an issue with the start capacitor, the switch, the motor, or something I don't know about. I have attached all the info from the instruction manual that I can find about the motor and wiring.

Thanks for the help - I'm currently without an income and if I need an electrician I'm going to be without a lathe or quite some time .

 

[Wizard69]

I'm far from an expert, but I'm not seeing a start capacitor in that drawing.

Given that your description does sound like a start circuit problem. If there is a cap in the machine it could be bad but don't dismiss the possibility of a bad centrifugal start switch in the motor itself. If the motor hums then it is single phasing for some reason.

This is a case where a decent multimeter could help a bit. If you don't have one, being able to establish continuity through the motor would be helpful. There are a couple of ways to ring out the wiring with things you might have in your junk box.

 

[Cogsy]

I do have a multimeter but very limited knowledge of what to do with it. I guess I'll start stripping the thing down tomorrow and see what's inside. I do know I haven't released the magic smoke yet.

 

[mu38&Bg#]

Check that you are getting voltage at all motor terminals to begin with. I would guess it's switch issue. Capacitors aren't usually intermittent. The cap is in the motor, so not in the diagram.

Greg

 

[Cogsy]

Thanks, I'll try that. I guess it could be the forward/reverse switch - that would make sense as I just disturbed it by using it.

 

[canadianhorsepower]

Thanks, I'll try that. I guess it could be the forward/reverse switch - that would make sense as I just disturbed it by using it.

Hi Cogsy.
buy this diagram you have a relay in it
and you don't have a capacitor if a variable speed motor

cheers

 

[Cogsy]

It's not a variable speed motor and there is a plastic cover on the outside of the motor that I always assumed was a start (or maybe run?) capacitor.

I'll definitely look at the relay, assuming I can find the thing. The thunking sound may well be a relay clicking, although it must be a lot bigger one than the auto ones I'm used to playing with. At least I know from you guys that there's no hidden capacitors waiting to shock me in there.

 

[canadianhorsepower]

It's not a variable speed motor and there is a plastic cover on the outside of the motor that I always assumed was a start (or maybe run?) capacitor.

If you want to check the capacitor with wires
disconnected short circuits both pins. Look away in case of sparks
it should sound like a shot gun if healthy

model and brand ???
Luc

 

[Cogsy]

model and brand ???

That's a more difficult question than it seems. We have a machinery company here in Australia called Hare and Forbes. They bring in mostly Chinese stuff and have it painted, branded and model numbered to their own designations. So it's a Hafco AL280-P, but that won't mean much to you. I'm sure it's probably been sold in North America as well, but under different names.

I'll head out to the shed now and see what I can find out. If I never post again you'll know I electrocuted myself .

 

[Cogsy]

Thanks for the help guys. The problem turned out to be the forward/reverse switch after all. As I was removing the push-on connectors to check it, the whole thing fell to bits. Looks like the bottom was only attached with 1 little dribble of glue in the centre.

The contacts were a little burnt from arcing, so I cleaned them up a little and did my best to re-assemble the switch. I wouldn't trust trying to switch it, but for now it's bodged good enough to run the lathe til I can source a replacement. I ran it for a while with multiple stop starts and only had 1 time it didn't start straight up, but I'm putting that down to those cruddy contacts.

Thanks again, without the help and advice I wouldn't have had the confidence even to open the thing up.

Here's a pic of the switch.

 

[tornitore45]

I would avoid reversing the motor under power, the reversing switch may be rated just to carry the current, not breaking it. The relay is probably rugged enough to break the current. Beside reversing under power is hell for the motor as well.

Operating the forward/reverse switch with power off should never produce contact arcing and last as long as the switch is mechanically sound.

 

[Cogsy]

I would avoid reversing the motor under power

I agree, I've never switched it under power and I wouldn't attempt it. The switch began to pull apart and let the contacts get sloppy. That's what was creating the starting problems and causing the arcing as well.

 

[tomrux]

A single phase motor will not reverse without first stopping. it will continue to run in the same direction.

Tom R