WIRELESS POWER TRANSFER

A wireless power transfer system comprises a power transmitter (101) wirelessly providing power to a power receiver (105) via an electromagnetic power transfer signal. The power transmitter (101) comprises a transmitter coil (103) generating the power transfer signal and a driver (201) generating a drive signal for the transmitter coil (103) to generate the power transfer signal. A foreign object detector (207) executes a foreign object detection operation arranged to detect a presence of a foreign object in response to a property of the drive signal. A communicator (205) receives a power operating point indication from the power receiver (105) which represents a load power for a load of the power receiver (105). An adapter (209) adapts the foreign object detection operation in response to the operating point indication being indicative of a change in the load power meeting a criterion.