Safety system and safety equipment

摘要

To provide the safety system and safety equipment that can be constituted by only one main magnetic contactor, although two main magnetic contactors have been required for duplication to interrupt the power supply to the three-phase motor started by star-delta starting. Two back electromotive force detection parts of a stop detection unit 3 are respectively connected to both ends of wiring of U-phase and W-phase of a three-phase motor 2. Therefore, a stop of the three-phase motor 2 can be detected, based on a back electromotive force generated in the wiring of the three-phase motor 2, in a state of turning off both of a star connecting switching device 8 and a delta connecting switching device 9, at the time of interrupting power supply in which a main switching device 7 is turned off. That is, there is no necessity for turning on either the star connecting switching device 8 or the delta connecting switching device 9 for detecting a back electromotive force, and therefore it is not necessary to provide two main switching devices 7 for duplication.