In a power generator, a determiner determines whether a phase voltage output from each of multiphase armature windings has exceeded a threshold voltage. A turn-on unit turns on at least one of the protective switches as a target protective switch to limit the output voltage of the rectifier circuit to be lower than the threshold voltage upon the phase voltage output from at least one of the multiphase armature windings corresponding to the at least one of the protective switches has exceeded the threshold voltage.