A synchronous motor/generator is modified by mounting the conventional rotor on a sleeve that rotates freely on the main shaft rather than being fixedly mounted on the shaft. Limits to this rotation are incorporated in the design such that the maximum angular rotation of the rotor on the shaft equals half the stator advance that occurs during a complete full cycle of the AC stator winding voltage. In addition to smoothing transients, this configuration permits the machine to smoothly drop into the correct stator/rotor flux phase when it changes from a motor to a generator, and back into the correct phase for a motor, when the AC power is interrupted, and subsequently resumes, resulting in dropping a single cycle.