Three phase motors are an order of magnitude cheaper.
Machines powered by three phase motors have inherently less vibration.
(Think about it - 120 times every second the power applied to a single
phase machine is instantaneously *zero* ..)
Many industrial motors e.g. motors that come on a Bridgeport mill are
much better quality than cheap single phase replacements.

Good question!

Grant Erwin

SRF wrote:
I'm setting up a hobby machine shop and am getting into the issue of 3 phase
motors. Most of the motors are going to be in the 1 to 3 horsepower range.
For motors of this size, why would I want to have make three phase power to
run these machines instead of just swapping out the motors for single phase?

Thanks.
Steve.