Re: Distractions....

David,

You can start a 3 phase motor on single phase current by spinning it up
with a rope (be sure not to engergize the motor until ALL the rope is
CLEAR of the shaft!) or using a smaller motor to get it going. The trick
to home made phase converters is the run capacitors used to balance the
voltage across all three legs.

My setup uses a momentary contact On/Off push button switch to activate
a relay. This relay engergizes a 3 pole relay and brings a start
capacitor into the circuit. As soon as I let go of the On button, the
first relay drops out taking the start cap out of the circuit. The 3
pole relay is held closed by power taken from one of the 3 legs. The
stop button is connected in series in this circuit, allowing the relay
to open the circuit. The hard part is a pair of very large capacitors
given to me by a friend of my dads.
There are two cans with two caps per can, sharing each sharing the
center of three taps. They are Sprague-Clorinal 17.5-17.5 @ 360 volts
AC. Can't pretend to know how they work, and can't easily explain how
they are wired in. Perhaps I can draw a schematic, scan, and post it.
Total cost was under $250 including the 3hp motor I bought used. I do
have fuses on the input, will be replacing these with breakers when I
step up to a 7.5hp motor in the future.

Static converters are nothing more than a start cap and a current
sensing relay that cuts the cap out when the inrush current drops to a
set level. That's why you derate motors when run on them.

Jon