Magnetic Shielding

Magnetic shielding in WPT redirects leakage flux away from sensitive areas: vehicle electronics, steel frames, operator-accessible surfaces, and neighboring pads. Shields may be ferrite back-plates, aluminum or copper plates (eddy-current shields), or laminated silicon steel depending on frequency and loss budget.

A shield always interacts with the coil — it lowers self-inductance, changes k, and can add loss if conductive shields are too close or too thick without analysis.

01Shield types

• Ferrite back-plate: guides flux, adds inductance, limited saturation headroom.
• Conductive sheet: reflects flux via eddy currents; frequency-dependent penetration depth.
• Hybrid ferrite + aluminum: common in receivers to protect battery enclosure electronics.

02Design rules

Place shields on the non-coupling side of the coil when possible. Maintain minimum air gaps between coil and conductive shield to control capacitance and loss. Validate with and without the vehicle chassis present — the dock alone is not the full system.

03Failure modes

• Saturated ferrite shield acts like air suddenly — detuning during high-power sessions.
• Loose steel shields vibrating in the field — audible noise and intermittent loss.
• Corrosion or fasteners penetrating shield continuity creating slot antennas.