Thread: Need help finding a capacitor for my lathe motor

Originally Posted by nadroj

My Ducati buddies sometimes tease poor old British bike owners for the alleged bad electrics.
I tell them that if my Ducati's were as good as Lucas, it'd be an improvement.

Jordan

Yes, British electrics don't work.

Italian electrics just pretend to work.

Rob

Originally Posted by Uncle Al

Can't imagine how much noise that would have created when spilling it's guts.
Bet you needed a good stiff drink to settle the nerves after that little incident.
Anyway, a new capacitor and a six pack of undies from K-Mart should get you back in business.

Alan...

Yep it made a hell of a bang and took about 2 hours for the workshop to clear of smoke. Stiff drink and new undies needed indeed.
No way i was putting 240v through that motor again, it lives in the scrap pile now. I ended up fitting the old 3hp 3 phase motor from my big mill and a VFD instead which is just great.

In a stange turn of coincidence one of the caps on my small mill melted a few days later, destroying the terminal box :S
No big explosion this time luckily!


The cap that spilled its guts was only 4 or 5 yrs old, hopefully no carcinogens! I still find little bits of oil soaked paper hiding in a corner or crevice occasionally...

Originally Posted by andrew_mx83

No way i was putting 240v through that motor again, it lives in the scrap pile now.

The motor usually is not the problem.

The cap just gets dried out or leaky and craps itself.

You can bridge out the cap wires and the motor should still start in a free running (nothing connected) state.

All the cap does is add extra volts to flash overload the motor to get it up to speed.

Rob

No thanks. The bang was violent enough for me to not want that to happen ever again.

Getting that motor to work correctly on the lathe had stretched the limits of my AC electrical knowledge and i did not wish to press my luck any further. This one had a run cap only (permanently connected), the one it was replacing had a start cap only (on a centrifugal switch). In the run cap only scenario you have to flip the cap over to a different set of windings to go forward and reverse, which is fine if you only want to go one way... but if you want both selectable by a switch then things get a bit complicated.

VFD solved all these problems, and more.

I think the one that blew on me was caused by low voltage. I was using an old generator to run the motor. I was at the motor, or shearing hand piece and just walked towards the gen set and bam. The gen set was a bit tricky to get running right until it had warmed up. I don't think it was running fast enough. Not like my current gen set that you just start, push in the choke and go. That was my first time running a gen set as well.

Dean

Got this capacitor in the mail today 16uF Multi Purpose NEW RUN Capacitor Suit 240V Motors | eBay But im wondering if it has a certain polarity? Or do i just wire it what ever way? If not ill just try and copy my other capacitor to the way it used to be wired

Cooper

Originally Posted by xXvapourXx

Got this capacitor in the mail today 16uF Multi Purpose NEW RUN Capacitor Suit 240V Motors | eBay But im wondering if it has a certain polarity? Or do i just wire it what ever way? If not ill just try and copy my other capacitor to the way it used to be wired

Cooper

same two wires anyway round...its an ambidextrous type...lol...they all are


Oh I see what your query is....it has four spade terminals....

two on each side are actually joined/connected...use any two that are not connected to each other

edit...put one wire on anyone of top two terminals you see in the pic, and a wire on any of the bottom two.

Originally Posted by eskimo

same two wires anyway round...its an ambidextrous type...lol...they all are


Oh I see what your query is....it has four spade terminals....

two on each side are actually joined/connected...use any two that are not connected to each other

edit...put one wire on anyone of top two terminals you see in the pic, and a wire on any of the bottom two.

Oh awesome, easier than what i thought! Thanks eskimo and to everyone else who helped out! ill let you guys know if its up and running

Cooper

well i replaced the capacitor and no luck :/ so i decided to take the motor off my lathe had a quick look around the motor to see what was wrong and couldn't find anything. After another search thinking that my motor is stuffed i saw this liitle black button that was hidden with the rest of the motor and i pushed it and it made a click sound, turned the power on to the motor and now its working hahahahahah, so now i know it wasnt the capacitor but it was that button which must have been a overload switch or some sort of safety switch hahaha o well typical me

Cooper

Originally Posted by nearnexus

You can bridge out the cap wires and the motor should still start in a free running (nothing connected) state.

All the cap does is add extra volts to flash overload the motor to get it up to speed.

Rob

Not quite correct, Rob. The capacitor in a single phase induction motor is what makes it want to spin, instead of just sitting still and humming. It doesn't do this by adding volts, but by creating torque.
With no cap, you can start it off with a light push of the shaft with your hand. Like a 2 stroke engine, once it's started, momentum will keep it spinning.

Jordan

Originally Posted by xXvapourXx

overload switch or some sort of safety switch

yep..its a thermal overload.

you must have had the motor under some load for it to trip....can you recall what you doing at the time immediately prior to the motor having stopped working

Originally Posted by eskimo

yep..its a thermal overload.

you must have had the motor under some load for it to trip....can you recall what you doing at the time immediately prior to the motor having stopped working

I was turning down some metal for my drill press for the motor to mount onto, i had also realised that it only does this at the highest speed.

Edit: Like these to metal rods on this plate http://i22.ebayimg.com/03/i/001/00/2c/2993_35.JPG