Electromagnetic Coupling Mechanisms Used in Wireless Power Transfers

September 2, 2021

Cadence System Analysis

Key Takeaways

Electromagnetic coupling is when the electromagnetic field in one circuit induces charge or voltage in others.
The power transfer between the source and load circuit through the electromagnetic coupling mechanism is possible only when there is a change in the electromagnetic field of the source circuit.
The electromagnetic coupling used for wireless power transfers can be broadly classified into near-field and far-field wireless power transfers.

An electromagnetic coupling mechanism is utilized in a wireless power transfer

Wireless power transfer (WPT) technology is an increasingly popular way to charge consumer electronics. This technology is also used for electric vehicles, wearable electronics, and biomedical equipment, allowing power to be transferred amongst electronic networks without wires. Electromagnetic coupling mechanisms are utilized in wireless power transfers. Electromagnetic coupling can be either inductively coupled wireless power transfers or capacitively coupled wireless power transfers.

Let’s take a closer look at electromagnetic coupling mechanisms and how they can be applied in various industries.

How Does Electromagnetic Coupling Work?

Electromagnetic coupling occurs when the electromagnetic field in one circuit induces charge or voltage in others. The charge or current generated from electromagnetic coupling in other circuits can be intentional or unintentional. When the electromagnetic coupling is unintentional, it’s harmful. Electromagnetic interference is a standard example of unintentional electromagnetic coupling.

However, intentional electromagnetic coupling is a foundational aspect of wireless power transfers. The principle of electromagnetic induction results in electromagnetic coupling, where the fields are coupled between two circuits. The power transfer between the source and load circuit through an electromagnetic coupling mechanism is possible with a change in the electromagnetic field of the source circuit. The power is transferred from the source circuit to the load circuit without any wires or physical contact.

How Are Electromagnetic Coupling Mechanisms Applied?

Electromagnetic coupling mechanisms are used for WPT in several industries:

Application	Purpose
Automobiles	General battery charging in electric vehicles.
Aerospace	Energy transfer to moving parts.
Consumer electronics	Wireless charging of mobile phones and laptops.
Biomedical	Provides power to implantable devices.
Industrial	For use in harsh and flammable environments.

The Types of Electromagnetic Coupling Mechanisms Used in Wireless Power Transfers

Different types of electromagnetic coupling mechanisms are used for various wireless power transfers. Let’s examine two types of wireless power transfers—near-field and far-field power transfers—and their respective electromagnetic coupling mechanisms.

Near-Field Wireless Power Transfers

A near-field wireless power transfer is also called a non-radiative power transfer. In near-field electromagnetic coupling, the power transfer occurs over short distances. Near-field electromagnetic coupling can be either inductive coupling or capacitive coupling.

In inductive coupling, the time-varying magnetic fields cause wireless power transfers between inductive coils.

In capacitive coupling, the time-varying electric fields are utilized for wireless power transfers between metal electrodes.

Far-Field Wireless Power Transfers

In far-field wireless power transfers, electromagnetic radiation couples with a receiver at which it is aimed, located across long distances. This type of electromagnetic coupling over far-fields is also called power beaming or the radiative technique.

Wireless Power Transfers Using Inductive Coupling

Near-field wireless power transfers utilizing inductive electromagnetic coupling are called inductively coupled wireless power transfers. In an inductively coupled wireless power transfer, inductance coils transfer power between a source and load circuit. Inductively coupled wireless power transfers consist of two coils—a transmitter coil and a receiver coil. The coils are magnetically coupled (mutual inductance) so that the time-varying magnetic field in the transmitter coil can induce a voltage in the receiver.

The efficiency of the power transfer depends on the coefficient of coupling between the transmitter and receiver coils. Tight coupling makes the transfer more efficient than loosely coupled inductive coils.

Wireless Power Transfers Using Capacitive Coupling

Like mutual inductance in inductive coupling, coupling capacitance is the key parameter in capacitively coupled wireless power transfers. This wireless technique uses two metal electrodes that are capacitively coupled for power transmission. The time-varying electric field in the transmitter electrode induces a voltage in the receiver electrode.

Since electromagnetic coupling mechanisms offer non-contactless power transfers, they are the safest way to charge your electronic devices and electric vehicles. Cadence software can assist you in the designing of wireless power transfer circuits.

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