Wiki article · Collection 03

Planar Coil

Engineering reference on Planar Coil for wireless power system design, integration, and deployment.

6 minArticle 20/50Coil Design

Planar Coil — educational diagram — Fig.: Educational diagram for “Planar Coil”.

Planar coils confine the winding to a thin layer parallel to the docking surface. They minimize Z height on vehicle bellies and floor tiles, which matters for AGV ground clearance and trip-hazard limits on pad protrusion.

Planar does not mean uniform current — trace width tapering, multiple layers, and hollow centers adjust resistance and inductance. Multi-layer planar coils add inter-layer capacitance that can appear in the MHz range, above fundamental WPT frequency but relevant for EMI and self-resonance.

01Construction types

Single-layer PCB: cost-effective, moderate Q.
Multi-layer PCB with stitched vias: higher L per area, via loss matters.
Flat litz spiral: highest Q for power class.
Copper sheet photo-etched: middle ground for prototype to production.

Planar Coil — supporting diagram — Fig.: Supporting illustration for “Planar Coil”.

02Thermal and current

Planar coils spread heat across the pad face — good for coupling to aluminum spreaders. Current crowding at inner turns limits continuous power; taper inner trace width or use parallel inner segments. Model AC loss at operating frequency before choosing oz/sq copper weight.

03Integration

Keep sensitive CAN/Ethernet cables out of the coil plane shadow.
Planar receiver often sits above ferrite tile with uniform thickness.
Encapsulation thickness adds to effective gap — include in all k calculations.