Abstract: A circuit for energizing and controlling a synchronous rotary machine which operates at variable speed and is fed by controlled static switches, wherein the stator of the rotating machine has a plurality n of polyphase windings where n is at least equal to two, each polyphase winding being fed by a static AC-AC converter (A, B) which constitutes an autosychronous inverter having a mains bridge (PRA, PRB) and a machine bridge (PMA, PMB) connected to each other by first and second DC conductors, and wherein the circuit has means for controlling the mains bridge of each converter in such a way that the sum of the DC currents (IA+IB) in said conductors of all the converters is proportional to a reference average current value.

Abstract: Apparatus for controlling a static AC/AC thyristor converter which supplies power to a synchronous rotating machine (7) at a variable frequency. The converter comprises a "machine" bridge (PM) and a "mains" bridge (PRA, PRB) connected to each other by a first conductor (9) and by a second conductor (10), together with an auxiliary connection (8) which connects the neutral point of the synchronous machine to a point (11) at the "mains" bridge end via which point current can be returned to a transformer which supplies power to said "mains" bridge. The control apparatus comprises means for controlling the "mains" bridge in such a way that the sum of the currents IA+IB of said first conductor (9) and of said second conductor (10) interconnecting the "machine" and "mains" bridges are equal to an average reference current.