Wireless Power Transfer

The traditional cable power transmission has the problem of aging, wear and producing an electric spark and so on. Meanwhile, it is difficult to use the cable to transmit electricity in some special occasions, such as high mountain and seabed, which greatly reduces the safety and reliability of its use. Therefore, with the development of technology, the wireless power transmission technology has made people look on it. Because it has the advantages of low wear rate, high reliability and safety, convenient and flexible use, beautiful appearance and so on.

At present, there are some ways in which the wireless power transfer technology, such as electromagnetic WPT, resonant WPT, electromagnetic radiation WPT and so on. Here we discuss the progress of WPT application in recent years and transmission mechanism and modeling of resonant WPT technology are discussed.

The technological and theoretical idea behind wireless charging was initially suggested by Nikola Tesla in the 1890s. However, technology has been harnessed in the last decade to the point where it offers real-world applications. Wireless Power is commonly referred by various names like Inductive Power Transfer (IPT), Inductive Coupling and Resonant Power Transfer (RPT). The same fundamental process namely the transmission of energy from a power source to an electrical load without connectors across an air gap is essentially described by these terms.

“Wireless power transfer technology is becoming one of the most emerging and promising technology with most highly expected market impacts in mobile and automotive industries. It can be widely applied to commercial products including wireless charging for a smartphone, note PC, home appliance, automotive vehicle, and implanted medical device. It will enable us to be free from inconvenient wiring and charging overheads in battery-based operating systems”.

In 1893, Nikola Tesla reinvented the illumination of vacuum bulbs without using wires for power transmission at the World Columbian Exposition in Chicago.

The basic working of wireless power involves the transmission of energy from a transmitter to a receiver via an oscillating magnetic field. To achieve this, Direct Current (DC) supplied by a power source is converted into high-frequency Alternating Current (AC). The AC energizes a copper wire coil in a transmitter that generates a magnetic field. Once a second receiver coil is placed within range of the magnetic field, it can induce an AC in the receiving coil.

To summarise:

•The ‘mains’ voltage is converted into an AC signal (Alternating Current), which is then sent to the transmitter coil via the electronic transmitter circuit.

•The AC current flowing through the transmitter coil induces a magnetic field which can extend to the receiver coil (which lies in relative proximity).

•The magnetic field then generates a current which flows through the coil of the receiving device. The process whereby energy is transmitted between the transmitter and receiver coil is also referred to as magnetic or resonant coupling and is achieved by both coils resonating at the same frequency. Current flowing within the receiver coil is converted into direct current (DC) by the receiver circuit, which can then be used to power the device.

Advantages:

•It reduces the cost associated with maintaining direct connectors.

•It provides greater convenience for charging of everyday electronic devices.
•It ensures safe power transfer to applications that need to remain sterile or hermetically sealed.
•It reduces the risk of corrosion as the electronics can be fully enclosed.
•It provides consistent power delivery to rotating, highly mobile industrial equipment.
•It delivers reliable power transfer in critical systems like wet, dirty and moving environments.