Three phase power has three "hot" wires, 120 degrees out of
	phase with each other.  These are usually used for large motors
	because it is more "efficient", provides a bit more starting torque,
	and because the motors are simpler and hence cheaper.

	You're most likely to encounter a 3 phase circuit that shows
	110 volts between any hot and ground, and 208 volts between
	any two hots.  The latter shows the difference between a normal
	220V/110V common neutral circuit, which is 240 volts between the
	two hots.  There are 3 phase circuits with different voltages.

	Bringing in a 3 phase feed to your house is usually
	ridiculously expensive, or impossible.  If the equipment you
	want to run has a standard motor mount, it is *MUCH* cheaper to
	buy a new 110V or 220V motor for it.  In some cases it is
	possible to run 3 phase equipment on ordinary power if you have
	a "capacitor start" unit, or use a larger motor as a
	(auto-)generator.  These are tricky, but are a good solution if
	the motor is non-standard size, or too expensive or too big to
	replace.  The Taunton Press book ``The Small Shop'' has an
	article on how to do this if you must.

	Note that you lose any possible electrical efficiency by using
	such a converter.  The laws of thermodynamics guarantee that.

© 2008 FAQS.ORG. All rights reserved.