To achieve lightweight firm power generation having superior startability and being capable of converting an energy with a high efficiency and to provide a power plant.

A permanent magnet for excitation is embedded in a disc type rotor manufactured of a firm lightweight diamagnetic material, and fixed poles for a coil core are arranged on both sides of a disc. Homopolar magnets are mounted on the coil core so as to repel magnetic poles of the permanent magnet for the rotor, respectively. An attraction force acting on the permanent magnet for the rotor and a core for the coil core is always offset by a resiliency of the homopolar-pole magnets mounted on the permanent magnet for the rotor and the coil core, and the load of the attraction force from the time of rotating shaft start to the time of rotation is reduced, and the problem is solved.