Wireless Electricity Transmission Basics: A Tutorial

This tutorial covers the basics of wireless electricity transmission, focusing on electromagnetic and resonance magnetic coupling methods. Electricity is an essential part of modern life, and wireless transmission offers a convenient alternative to traditional wired power.

Before diving into the specifics of wireless electricity, let’s define some key terms:

• Electricity: The flow of electrons through a conductor (like a wire) or the movement of charges through the atmosphere.

• Magnetism: The phenomenon where certain materials attract or repel each other. Magnets and the Earth’s magnetic field are examples. Time-varying magnetic fields are created by passing AC current through a wire. Electric current flowing through a wire generates a magnetic field around it.

• Electromagnetism: The combined interaction of electric and magnetic fields. An oscillating magnetic field generates an electric field, and vice versa.

• Magnetic Induction: Using a conductive loop or coil carrying alternating current (AC) to generate and capture a magnetic field. This is a very efficient method.

• Energy or Power Coupling: When one object can transfer energy to another.

• Resonance: A property of physical systems where energy is efficiently added to an oscillating system at a specific natural frequency. This resonant frequency depends on the size, shape, and thickness of the material. A classic example is a child on a swing, where pushing at the right moment increases the swing’s amplitude.

Wireless Electricity Technology Overview

Figure 1 illustrates the basic principle of wireless electricity, which relies on coupled resonant objects to transfer electricity without wires. The system typically includes a DC/AC inverter, a split transformer, a transmitting inductor, a receiving inductor, a rectifier with a filter, and a linear voltage regulation circuit. Energy is transferred between the base unit and the portable device via magnetic induction.

How Wireless Electricity Transmission Works

Let’s examine how wireless electricity transmission functions over shorter distances. When a conductive loop is powered by an AC source, it generates an oscillating magnetic field around the loop (coil). A second conductive loop positioned near the first captures a portion of this oscillating magnetic field. This induces an electric current in the secondary coil, which can then power electrical or electronic devices. This principle is similar to that of an electrical transformer.

For the system to function efficiently, the receiver must be within range of the transmitter.

• Circuit A (Fig. 2): Converts 60Hz current to 10 MHz and feeds it to the transmitting coil (B).

• Transmitting Coil (B): Emits a 10MHz magnetic field due to the oscillating current within the coil.

• Receiving Coil (C): Resonates at the same frequency as the transmitting coil (magnetic induction). This coil picks up energy from the magnetic field emitted by coil B.

• Energy Transfer: The energy from the oscillating magnetic field induces current in the receiving coil (C), lighting the bulb (D).

Advantages and Applications of Wireless Electricity

Wireless electricity offers several advantages:

• Convenience and Reliability: It eliminates the need for cables, making it more convenient and potentially more reliable (less prone to cable damage).

• Environmentally Friendly: Reduces cable clutter and waste.

Applications span various power levels:

• Low, Full, and High Power Products: Wireless charging pads for phones, laptops, and potentially even electric vehicles.

• Industrial Applications: Mining, robotics, drilling, packaging machinery - where wires can be cumbersome or dangerous.

• Medical Applications: MRI machines utilize magnetic resonance imaging to produce diagnostic images of soft tissues.