Abstract: A mobile AC power source is described for generating AC electrical power that is powered by any rotational energy source such as a vehicle engine. The output of the mobile generator is sinusoidal but could have other shapes as well and is stable with variations in load and engine RPM. The AC output can vary in voltage from approximately 100 to 500 VAC RMS and in frequency from approximately 40 to 400 Hz. The mobile AC power source employs an alternator driven by the vehicle engine or any other rotational source and incorporates two stator windings and one rotor, or two stators, four windings and two rotors on a common shaft. The stator windings are insulated electrically from each other. AC output voltage is held constant by using the voltage produced by the alternator as feedback and controlling the alternator rotor current. A voltage step up circuit boosts the voltage from the alternator if it is below a threshold value as occurs at low engine RPM.