To constitute a safety apparatus only with one main magnet connector although two magnet connectors are required to interrupt power supply to a three-phase motor to star delta start for duplication in a conventional system.
Since two back electromotive force detection parts of a stop detection unit 3 are connected to both ends of winding of U-phase and W-phase in the three-phase motor 2 in the safety apparatus, stop of the three-phase motor 2 can be detected based on a back electromotive force occurring in winding of the three-phase motor 2 in a state where a star connection switch 8 and a delta connection switch 9 are turned off at the time of power supply interruption when a main switch 7 is turned off. Namely, it is not necessary to install two main switches 7 for duplication since it is not necessary to turn on the star connection switch 8 or the delta connection switch 9 for detecting the back electromotive force.
NAKAYAMA AKIYUKI
HIGUCHI TOSHIYUKI
HASHIMOTO MINORU
KAMIZONO DAICHI
