Motor capacitor sizing

[KenC]

I have an old motor on a brick saw that I picked up at an auction. It is a dual voltage 1725 rpm motor. Both the start and run caps are bad(split and corroded). But the windings appear to be good, no shorts or grounds that I can see with a meter.

It is 3hp motor that runs on either 120 or 240v, wired with 10g wire on the saw, and the voltage is switchable using a switch mounted on the wiring box.

I've not been able to get any info on the cap sizing from Baldor, likely because it is an obsolete item.

Finally my question: are there any sources to estimate cap sizing for these? I'd like to try it out with some used caps before sinking a lot of money into it.

 

[pattenp]

This is ballpark but is fairly standard for 240V 3-5 hp motors. 370V 20UF for the run and 250V 161-193 MFD for the start.

 

[KenC]

Thanks, I'll give that a try.

 

[RECox286]

Do you have a motor shop nearby ? They should have or be able to

get what you need.

Uncle Bob

 

[Socophreak]

Any motor rebuild place should carry what you want. Bring the caps with you. If you can get the information off of the capacitors that would be the best.

You should also be able to find caps on ebay as well if a local shop wont sell to you.

 

[KenC]

Thanks for the suggestions. No local motor shop, 45min one way drive and the old caps are so badly corroded on the outside that no legible info is available.

Used caps are available on eBay or several other places on the web. Now that I have a starting point I'll be ordering some.

I assume (darn that word) that after installing them and it runs (I hope) that I should measure the running amps under load to determine if I selected the right value.