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Message: <blockquote data-quote="Ahall" data-source="post: 3954309" data-attributes="member: 49426">A tread mill has to run at a variety of speeds.  That means some kind of variable speed drive.Old school was a mechanical belt and cone pully system or a DC motor with a voltage controller.Printed circuit boards have changed all of that.  3 phase motors are inexpensive and its easy to vary speed using modern electronics.That motor is 3 phase, and that makes sense.  Somewhere in the system there is a circuit board that converts your single phase AC signal to DC and then chops up the DC signal into a simulated 3 phase signal.  The really cool part is the board can also output the simulated 3 phase AC signal at any frequency you want.  The change in frequency is what changes the speed of the motor - your basic variable frequency drive (VFD).  You may also have a transformer that bumps the voltage up prior to the VFD.This type of system is common today.  I have seen it on variable speed pool pumps, in some air conditioners, and on many stationary tools.   If 3 techs can get it right, something is bad wrong or the techs are incompetent.  If its under warranty, neither are your problem.  Get a replacement machine.</blockquote>