Patent ID: 11894696
Assignee: UNIVERSITAT STUTTGART
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  B  Y | IPC B  H

Claim 7:
8. Apparatus for detecting electrically conductive foreign bodies during inductive energy transmission between a primary coil (1) and a secondary coil (2), in particular during inductive charging processes, which apparatus has at least one sensor coil (5) arranged above the primary coil (1),
characterized in that
the sensor coil (5) is connected to at least one capacitor (C3s) to form a close resonant circuit which is matched to an excitation frequency of the primary coil (1) and is connected to an evaluating device (6) which detects the current in the closed resonant circuit and which determines from a phase position of the current in the resonant circuit in relation to a reference signal whether one or multiple electrically conductive foreign bodies (4) are present between the primary coil (1) and the secondary coil (2);
wherein the evaluating device (6) is designed such that it uses a voltage at the primary coil (1) as the reference signal, or the primary coil (1) is connected to an excitation circuit which uses a PWM signal to excite the primary coil (1), and the evaluating device (6) is designed such that it uses the PWM signal as the reference signal.