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==== Shielding techniques of an IPT system ====

Shielding plays a crucial role in improving the power transfer efficiency, limiting EMI and protection nearby electronic devices from inducing currents. There are three common methods used:

* Ferrite shielding

Ferrite materials have high magnetic permeability and acceptable loss. Placing a ferrite slab or sheet behind a coil redirects magnetic flux toward the receiver coil, improving coupling. As a result, overall system efficiency is improved. However, ferrites are brittle and relatively heavy, which can add design limitations. They also tend to saturate at high magnetic flux densities and may become expensive when used in large-scale applications. For low-frequency applications MnZn ferrites are preferred, while NiZn ferrites are used at higher frequencies. These ferrites can come as rigid tiles, bars or in flexible sheet form.

* Conductive metal shielding
Conductive shielding works with the principle of eddy current induction. Conductive materials generate currents that produce opposing magnetic fields. This reduces EMI when placed behind or around coils. Aluminium is mostly used over copper due to its light weight, good conductivity, and low cost. Copper offers superior shielding performance but at a higher weight and cost.

This technique is especially used when the protecting of nearby electronics or structural components is important. However, conductive shielding can introduce resistive losses that lowers the system’s efficiency. It can also reduce the coil's quality factor if placed too close, leading to again efficiency drops of the system. These drawbacks can be reduced by using slotted or meshed plates and applying spacing between the shield and coil.

* Magnetic flux guidance

Ferrite structures are used to guide magnetic flux between the transmitter and the receiver. By focusing the magnetic path, the coupling efficiency is increased while also minimizing leakage fields. Flux guides are particularly effective in scenarios where alignment between transmitter and receiver is dynamic or difficult to control, such as in wireless charging systems. They also introduce added weight, structural complexity and improper placement can reduce the effectiveness of the system [92], [93].

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