FOREIGN OBJECT DETECTION IN A WIRELESS POWER TRANSFER SYSTEM

A wireless power transfer system includes a power receiver () receiving a power transfer from a power transmitter () via a wireless inductive power transfer signal. The power transmitter () comprises a transmit power coil () generating the power transfer signal. A test signal coil () coupled to a test signal generator () generates a magnetic test signal. A plurality of spatially distributed detection coils () is coupled to measurement unit () generating a set of measurement values reflecting signals induced in the detection coils () by the magnetic test signal. A processor () determines a measurement spatial distribution of the measurement value where the spatial distribution reflects positions of the detection coils (). A foreign object detector () detects a presence of a foreign object in response to a comparison of the measurement spatial distribution to a reference spatial distribution. The foreign object detector () is arranged to determine the reference spatial distribution in response to data received from the power receiving device ().