PURPOSE: To monitor arcs generated in a plurality of brushes, by a simple and cheap configuration, in an arc monitoring apparatus which monitors the arcs generated in the brushes of a rotating electric machine.
CONSTITUTION: A plurality of optical fibers 3 are so provided that their one-ends are respectively opposed to the parts wherein a collector ring 1 is contacted in a sliding way with brushes 2 in a rotating electric machine. The other ends of the optical fibers 3 are mounted on the input side of an optical path switching device 4, and another optical fiber 7 is mounted on the output side of the optical path switching device 4. The output beam of the optical fiber 7 is given to a photoelectric conversion element 8, and it is converted into an electric signal 9. Further, the electric signal is amplified by an amplifier 10, and the output of the amplifier 10 is given to an abnormality sensing circuit 11, and the generating states of arcs are decided. Still, using a switching signal 6 given from a switching signal generator 5, the output beam of only one optical fiber is selected by the optical path switching device 4 among the ones of a plurality of optical fibers 3, and this output beam is transmitted while being switched in succession to the other one optical fiber 7 on the output side of the device 4.
Akihiro Miyaji
Juichi Oide
Tohoku Electric Power Co., Inc.