Electrolytic "start" caps are not suitable for use as running caps. They
will blow up if left in circuit form more than a few seconds. You can't use
them for run "test caps" as you suggest - they will blow! With a 15 HP
idler motor you will need around 450 microfarads of run capacitance
permanently connected from one side of the input line to the "manufactured
phase". This will result in an "unbalanced" but satisfactory rotary phase
converter. Start by putting in 350 microfarads, or so, and add capacitance
while metering the manufactured phase. Continue to add capacitance until
the manuf. leg voltage rises to approximately 10% greater than the input
(240 ?) volt input line voltage. Be very careful - you are working with
lethal voltages!

Bob Swinney
S
"gtslabs" wrote in message
ups.com...
Thanks I see the difference now. I have a case of ~130 uF 240V
electrolytic caps. I know these are not for continious use but only
start-up. However I would like to use these to find the correct
capacitance needed then buy the oil run type caps. How long is safe to
run these caps in a continious mode for testing?