just my luck

[JWD]

Hi all, some of you may have seen my post in woodturning waxing on about my new lathe and how great it is. A grand total of 5 minutes after this the motor just stopped with absolutely no warning

I do intend to change it up for a new motor anyway but i now feel i need closure on this one

it cant be the fuse as i can hear the NVR switch hum when it turns on...
i dont *think* it's the capacitor(s) as the motor doesn't even try and move which in my experience does occur when the capacitor has failed.

I'm thinking possible loose connection? i don't know how else it could've just stopped like that... Frustratingly i've had to abandon it to come to uni until friday so now is brainstorming time!!

any advice/ideas would be so very much appreciated
JD

 

[Sideways]

You need a test meter.
Check that the power is getting to the motor when you press the start button.
Check that the power stays on when you let go of the start button and that pressing stop disconnects it.
After that, you should note that your motor has two capacitors, one is connected for a second or so at startup to give a torque boost to get the motor and big lumps of wood moving, then a centrifugal switch in the fan end of the motor will disconnect it and the motor will continue to run using the other capacitor.
This is a little more complicated than the commoner arrangement with just one capacitor connected all the time. The benefit is greater starting torque.
Centrifugal switches quite often fail and need to be dismantled, cleaned and put back together. They are mechanical so prone to wear. That's the next step to explore if you find that the NVR switch is operating properly.
That's a big solid lathe you have there

 

[lurker]

Nv switch full of sawdust??

 

[JWD]

NVR looks clean to me, lurker

So if it is dual capacitor, does that mean it could well have just stopped running suddenly? when i switch the NVR on it hums but the motor doesnt make a sound :?

thanks guys

 

[Ttrees]

This could be the problem....
There has been discussions here before about the pulley system "reeves drive" on variable speed lathes needing lubrication
Chas CHJ normally dwells in the lathe section and has mentioned this.
post1094028.html#p1094028

I have lubricated the reeves drive shaft on my SIP lathe and it has helped.
I still need to manually spin the timber to get her goin...
I'm unsure what speed I do this at, but with a bit of trial and error it may get your lathe spinning again.
Good luck
Tom

 

[sunnybob]

The NVR switch should not hum.

Easy to test. Remove the machine from the electric supply, pull the NVR switch, connect blue to blue and brown to brown, make sure the temporary connections can not touch bare metal or people. Reconnect and use the wall socket switch to test. If the motor turns, throw the switch away. If it doesnt, I would still throw it away but carry on to the capacitors.
NVR switches should not hum.

 

[JWD]

Sunnybob, good to know! i'm going to just wire it up straight to a plug and test it from the mains - it's a shame really as i wanted to use the NVR for my homemade 2x72 grinder but will have to find a new one

you have given me some hope!

Joe

 

[sunnybob]

I had a brand new drill press delivered to me.
When I assembled it and turned it on, the NVR switch did work, but hummed loudly. Luckily I have electrical and mechanical fault finding skills. I inspected the wiring and found the switch had been wired incorrectly at the factory.

If your machine does work when the switch is wired out, maybe my advice to throw it anyway was a bit extreme. The back of the switch has 4 connections. 2 wires in from the mains, and two wires out to the motor. Inspect the back very carefully and you should see each connection labelled L and N.
If you reconnect that switch EXACTLY as specified and it works, then youre good to go.
This applies even if the machine still does not work, move onto the capacitors and then the motor, but dont toss the switch untill you have the motor running and then reinstall the switch correctly to test it. But one more time, it should not hum.

 

[JWD]

Motor is working again thank you for all your help!

 

[sunnybob]

aw cmon... WHY is it working again??????? (hammer) (hammer) (hammer) (hammer)

 

[JWD]

what i assume was a knackered NVR/loose connection, as soon as i plugged it direct to mains it started up!
Sunnybob do you have any good resources for understanding NVR's/ motors?

 

[sunnybob]

The NVR is a double isolating switch. If the power fails for any reason, the NVR fails safe, disconnecting both live and neutral wires which means the motor can not start up by itself when the power is restored.

The lower pair of wires (line in) is run through a small coil electromagnet. When you press the start button you complete the circuit and the electromagnet holds down a little hinged paddle. This paddle has two contacts on it which when pulled down, contact the two line out wires and the motor runs.

When the power fails the electromagnet stops working, and this allows the paddle to spring back up, disconnecting the two motor wires.
Only by pressing the start switch again can the motor be re energised.

Its possible to get weird symptoms by reversing the wires (loud humming).
But if the tiny copper wound coil suffers a full or partial mechanical breakdown then erratic behaviour follows, which also includes humming.

One of the first woodworking machines I bought was faulty from the box. Plug it in the wall and the motor started and kept running. Press the start button and the motor stopped. But only as long as you held the start button in. Let go, and it ran again. The NVR switch had been wired backwards in the factory (chinese quality control, dont you just love it?)

If you have put the wires back in the correct location and the machine works, then you have a good chance of it working for a very long time. If it doesnt work, bin the switch. There are no user serviceable parts inside.

 

[Ttrees]

Nice job Bob =D>
Bob, Robert Minchin has wrote a really helpful article in PDF on induction motors and switches.
The link is here, at the bottom of his post, for some reason I can't just give the direct link ...
http://www.thewoodhaven2.co.uk/viewtopi ... r+pdf#p514


Tom