Diesel,
Don't think Allis Chalmers was working on an AC drive system in the 1970's. They first introduced a tranistor based control in 1965 called PWM (pulse width modulation).
Around 1974 the PWM control was changed to the ACtronic control. It was still a transistor control using DC motors and controls. At that time they were using Allis Chalmers built drive and hydraulic motors.
Worked for the AC factory in there product development group from 1967 thru 1982
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