Abstract: A power supply system includes a regulated power source that has an a synchronous machine, a flywheel with the shaft connected thereto, an electrical generator electrically connected through a switch to the synchronous machine of the regulated power source, an engine having a main shaft coupled to the shaft of the electrical generator, a power supply, and a switch connected between the electrical generator, the power supply and the regulated power source. The switch transfers power from the regulated power source to the electrical generator so as to cause the electrical generator to rotate the shaft in order to rotate the shaft of the engine during engine start-up.