EMI Basics

Electromagnetic interference (EMI) is any unwanted electromagnetic energy that degrades the performance of nearby equipment or causes a product to exceed regulatory emission limits. In SiCore wireless power systems, primary EMI sources include full-bridge or half-bridge inverters switching 400 V DC at 85–150 kHz for resonant tank excitation, gate-driver edges in the 10–50 ns range, and synchronous rectifier transitions on AGV receiver boards carrying 80–150 A. Secondary sources — ferrite saturation harmonics, DC bus ripple, and communication transceivers — contribute at distinct frequency bands that require separate mitigation strategies.

Factory AGV deployments add environmental complexity: dense Wi-Fi and private LTE, variable-frequency drives on conveyor systems, arc welders in adjacent bays, and steel floor structures that reshape radiated field patterns around floor-flush charging pads. SiCore EMI engineering treats dock transmitters and onboard receivers as co-located aggressors and victims simultaneously — a receiver rectifier can pollute CAN and safety IO while the dock inverter couples into facility mains.

01Emission and susceptibility

• Conducted emission: high-frequency current injected onto AC mains, DC supply, and battery return paths via power cables and facility grounding.
• Radiated emission: E-field and H-field energy from coil windings, switching loops, cable harnesses, and enclosure apertures.
• Conducted susceptibility: product malfunction when noise enters via power ports — relevant for dock AC front-end and vehicle DC bus.
• Radiated susceptibility: demodulated or logic-level disruption from external fields — alignment sensors, wireless comms, and safety interlocks.
• Common-mode vs differential-mode: CM noise dominates long harness runs and facility ground; DM noise dominates local inverter loops.

02Coupling mechanisms in WPT hardware

Capacitive coupling transfers energy across insulation gaps — from high dv/dt nodes on the resonant tank to nearby steel floor plates, vehicle frames, and alignment sense electrodes. Inductive coupling links switching current loops to parallel harnesses and CAN wiring routed under AGV belly pans without adequate separation. Conductive coupling shares ground impedance between dock electronics, facility earth, and vehicle chassis — a path often underestimated when commissioning multiple pads on a common concrete slab.

Resonant WPT operation intentionally creates strong H-fields at the charge frequency; EMI engineering distinguishes intentional power transfer from parasitic harmonics and subharmonics that extend into CISPR-defined bands. Misaligned coils increase reflected power and inverter stress, often raising harmonic content before thermal limits are reached — EMI is frequently the first observable symptom of mechanical wear.

03Design lifecycle integration

SiCore integrates EMI analysis at schematic, layout, mechanical, and firmware stages — not as a pre-certification afterthought. Pre-compliance scans on engineering builds identify dominant harmonics and loop areas; layout revisions target switching node compactness, return path continuity, and filter placement before tooling commits. Fleet telemetry correlates EMI-related faults — CAN errors during charge, spurious safety interlock trips, and mains breaker nuisance trips — with pad firmware revision and site grounding audit status.