Wiki article · Collection 03

Foreign Metal Near Coils

Engineering reference on Foreign Metal Near Coils for wireless power system design, integration, and deployment.

6 minArticle 42/50Coil Design

Foreign Metal Near Coils — educational diagram — Fig.: Educational diagram for “Foreign Metal Near Coils”.

Foreign metal near coils includes intentional (chassis, rebar) and accidental (wrench left on pad, metal shavings, foil packaging) conductors and permeable objects. Time-varying fields induce eddy currents that dissipate heat, reflect flux, and detune resonant tanks. Ferromagnetic debris can saturate locally and trigger FOD or hide real faults.

Dirty warehouse environments require pads and receivers designed assuming occasional metal presence — not only clean-room commissioning.

01Effects

Reduced or shifted k and L — power derate or control hunt.
Hot metal — fire risk with thin shavings on energized pads.
False FOD or missed FOD depending on algorithm and object size.
Audible vibration on loose ferrous parts.

Foreign Metal Near Coils — supporting diagram — Fig.: Supporting illustration for “Foreign Metal Near Coils”.

02Design responses

FOD tuning for site-typical debris. Pad surface slopes and covers to shed metal. Receiver skid plates that keep coil face clear. Maintenance SOP: visual sweep before energizing after floor work.

03Testing

Standardized metal plates and shavings at defined locations in qualification.
Repeat after encapsulation wear exposes coil area differently.
Log FOD trips in fleet telemetry for pattern analysis (nail vs rebar shift).