In a message dated 3/1/2005 3:32:20 PM Eastern Standard Time, olin_piclist@embedinc.com writes: The real point behind 3 phase power is that total power delivered is constant and does not vary with the 60Hz or 50Hz power cycle. Three phases is the minimum required for this to be true. Among other things, this means that the torque on the generators at power plants is constant. This is very important for such high power machines. This also means that 3 phase motors draw a constant power and put out a constant torque. This is true, and yes, it is a major reason you use three phase motors on industrial machinery, we use them in almost all applications no matter how small the power requirement. Some of the axis positioning motors for "go to and stop" axis positioning use motors as small as 1/8 Hp with electro-mechanical brakes on them. Can you imagine what the power usage would be using single phase motors, some of which would need to be 200 Hp or so and say 50 to 60 of those 1/8 Hp motors on a single machine. Wouldn't want to pay that power bill. Another thing that is good about 3 phase is the ability to virtually reverse thier direction instantaneously and of course how easy it is to do that, simply two of the wires using a second motor starter, etc. As well as reduced starting currents by using wye-delta starting, no special transformers, electronics, etc. needed in most applications. Randy Abernathy 4626 Old Stilesboro Road NW Acworth, GA 30101-4066 Phone / Fax: 770-974-5295 Mobile: 678-772-4113 E-mail: cnc002@aol.com I furnish technical support, repair, and other related services for your industrial woodworking machinery. My background as Senior Service Engineer for the SCMI Group for nearly fifteen years with factory training, combines with my extensive background in electronics, mechanics, pneumatics, electrical and CNC machinery to offer you needed support for your machinery. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist