Disclosed herein is a centralized power reducing device, particularly for lighting installations, comprising, on each phase of the installation power source, a winding (16) in series with load (10), wound on a magnetic core (18), the current supplied to load (10) flowing therethrough, a second winding (20) wound on said magnetic core (18), a drive or control current flowing therethrough, means (22, 24) for changing said drive or control current and characterized in that said means (22, 24) for establishing the extent of the drive or control current in said second winding (20) are comprised of a multiple-tap autotransformer (22), the connection of said autotransformer (22) taps occuring by means of relays (24) controlled by a logic unit (26).