A spokesman for Japan's nuclear and Industrial Safety Agency, the nation's nuclear-power regulator, said Fukushima Daiichi's emergency-generator design is "fairly prevalent" at other Japanese plants.

The role of the regulator is to ensure that the generator output voltage to maintain a constant energy, protect the safe operation of equipment.

A design and research of microcomputer excitation regulator for synchronous generator based on AT89C52 chip microcomputer is introduced.