Melted Capacitor.

[Tiger t]

I have a 3hp three phase motor in my lathe. I run this on a rotary phase converter, but unfortunately two start/run capacitors have burnt out and melted in the converter. One capacitor still has the identification marks visible, but the other one ( slightly smaller in size ) has melted and destroyed the markings. Is there any way that I can determine what capacitor i need to replace this.
Any help will be much appreciated.

 

[pe2dave]

If the larger is 50 micro farads, how much smaller is the small one?
Would suggest, if the larger will fit in the space for the smaller, buy two similar ones.
Ensure the working voltage is same or more? If you can find a 33 micro farad,
as a guess, I doubt it will harm, though I would perhaps wonder why both have gone?
I.e. is there an underlying cause? Is anything else damaged?

 

[Tiger t]

Hi Dave, thank you for your reply. I will measure them and post the sizes.
I have been using my lathe with this converter for twenty years. A few years back I changed the capacitors ( pity I didn’t keep the receipt ) because the converter stopped working. The other day I was using my lathe, but something didn’t sound right, so I turned everything off and noticed smoke coming from the converter. It’s been really reliable over the years apart from the capacitors.

 

[pe2dave]

Very crude, but any caps, of the same working voltage and roughly the same capacitance, should do
the job?
If you have the maker of the converter (???) ask them directly - or worst case, hunt for an equivalent
converter - I've no idea of prices.

 

[pe2dave]

Looking at it, the cap seems 400V working (can you read it any better?)
If it's 3 phase, working v will peak at higher (anyone?) than that?
Could be the cause - too low a working voltage? Not home ground for me.

 

[Tiger t]

Looking at it, the cap seems 400V working (can you read it any better?)
If it's 3 phase, working v will peak at higher (anyone?) than that?
Could be the cause - too low a working voltage? Not home ground for me.

I’ve managed to find where I bought the capacitors from, complete with a reference ID, so hopefully I might be able to find out what they were when I call them on Monday.