Switching unit for auxiliary power supplies - has connections and oppositely acting switches for mains and stand by supplies and overload switch

摘要

The control unit for alternative connection of an emergency electrical power supply or mains supply to a domestic or other installation has a housing (10) with sockets (20,30) for the two alternative supplies, and an output connection (40). Between the mains supply socket (20) and the output is a switch (25) operated by a relay, and between the alternative connection (30) and the output is a second relay operated switch (35). A control device ensures that when the mains supply fails, the first switch is disconnected and the second switch is closed. Also included in series with the second switch is a further switch (37) forming an overload safety cut-out. An acoustic device and warning lamps indicate the switching state.