Inductive power transfer system and method for operating an inductive power transfer system

An inductive power transfer system, in particular a battery charging system comprises: ¢ a transmitter coil (3) and a receiver coil (4); ¢ a transmitter-side power converter (8) comprising a mains rectifier stage (11) powering a transmitter-side dc-bus (10) and controlling a transmitter-side dc-bus voltage U 1,dc ; ¢ a transmitter-side inverter stage (9) with switching frequency f sw supplying the transmitter (3) coil with an alternating current; ¢ a receiver-side power converter (12) comprising a receiver-side rectifier stage (13) rectifying a voltage induced in the receiver coil (4) and powering a receiver-side dc-bus (14) and a receiver-side charging converter (15) controlling a receiver-side dc-bus voltage U 2,dc ; ¢ power controllers (19, 18) determining, from a power transfer efficiency of the power transfer, reference values U 1,dc *, U 2,dc * for the transmitter and receiver side dc-bus voltages; ¢ an inverter stage switching controller (20) controlling the switching frequency f sw to reduce losses in the transmitter-side inverter stage (9).