"Jess" wrote in message
...
Hi all,

I would like some help / advice in outfitting my shop.

For the first time in my metalworking home shop, I am able to get 3
phase service from the local power company.

In the past, I have always used a 3 phase rotary converter that I
built with the help of the group here - special thanks to Fitch and
Bob Campbell.

My question is, which voltage should I specify - and why?

I can get 208v, 220v or 440v.

I have three phase, and have had it as long as I've had a shop (since '67).
First shop was an open delta system, which is fine for light duty----no
large motors, say, under 7-1/2 hp.. I now have a 400 amp service, again,
delta. I had the option of 480, but didn't want to deal with the higher
voltage, even though one of my machines (a cylindrical universal grinder)
requires 480 volts. I have a transformer for that one machine.

The one negative is that with a delta service, you have a wild leg (208
volts, the B phase) that can't be used for 120V service. That's no big
deal, but it costs you one space out of three on your panel. You can use
the space for 240 volts single phase, however, so something like a welder or
water heater can occupy the otherwise unused space. If you select a
delta service (240 volts), be sure to keep that in mind so you size your
panel properly. The advantage of delta over wye (star) is the 240 volts
instead of 208. Motors will run cooler--although you're not supposed to be
sacrificing any power with the wye system. Dunno, I'm not an EE, nor an
electrician. I do know that a close friend had problems with some CNC
grinders when he moved to his new shop, equipped with 208 volts instead of
240.

Hope this helps more than it confuses.

Harold