On Wed, 18 Jul 2018 19:36:47 -0700, Jeff Liebermann
wrote:

On Wed, 18 Jul 2018 13:18:42 -0700, wrote:

Any reason for not disclosing the motor model number? Yes, I know
it's 40 years old and Granger can't find it.

There are two caps in most such motors. One is the "starting
capacitor". The other is the "run capacitor".
https://www.youtube.com/watch?v=qsuzfz5qcIE
https://www.youtube.com/watch?v=OMd9QkinXz4
I'm fairly sure they should NOT be wired in parallel.

For 220VAC, the starting cap should be about 30 to 50uF/kW.
3HP(mechanical) = 2.2kW so try about 90uF.

The run cap is usually about 5 - 20uF.

For the starting capacitor calculations, see:
https://www.electricneutron.com/electric-motor/single-phase-capacitor-sizing/
https://www.quora.com/How-do-I-calculate-capacitor-value-for-single-phase-motor
Mo
https://www.google.com/search?q=calculate+motor+starting+capacitor

I couldn't find anything on calculating the run capacitor.
The model number is 90653-N. The motor has only two wires coming out
to connect to the caps, so there is no starting cap. I tried a known
good cap that is about 200 MFD and it won't start the motor. The motor
tries to turn and I bet if I took the belts off it would start
spinning. The motor does spin easily enough but with the compressor
load it takes so long to spin up with the 200 MFD cap I'm afraid the
motor will overheat or the breaker will pop and so I turned it off
after a few seconds.
The compressor is a two stage air compressor that came with the
motor as a set. The compressor is unloading properly so the motor is
not trying to spin up a huge load and the motor has been spinning the
compressor just fine for the last 40 or 50 years.
I find it odd that there is no running cap but there just plain
aren't connections for one.
Eric