1. Introduction
Wireless power transmission (WPT) is an efficient way
for the transmission of electric power from one point to
another through vacuum or atmosphere without the use of
wire or any substance. By using WPT, power can be
transmitted using inductive coupling for short range,
resonant induction for mid-range and Electromagnetic
wave power transfer. By using this technology, it is
possible to supply power to places, which is hard to do
using conventional wires. Currently, the use of inductive
coupling is in development and research phases.
The most common wireless power transfer technologies
are the electromagnetic induction and the microwave power
transfer. For efficient midrange power transfer, the wireless
power transfer system must satisfy three conditions: (a) high
efficiency, (b) large air gap, (c) high power. The microwave
power transfer has a low efficiency. For near field power
transfer this method may be inefficient, since it involves
radiation of electromagnetic waves. Wireless power transfer
canbe done via electric field coupling, but electric field
coupling provides an inductively loaded electrical dipole that
is an open capacitor or dielectric disk. Extraneous objects
may provide a relatively strong influence on electric field
coupling. Magnetic field coupling may be preferred, since
extraneous objects in a magnetic field have the same
magnetic properties as empty space.
Electromagnetic induction method has short range. Since
magnetic field coupling is a non-radiative power transfer
method, it has higher efficiency. However, power transfer
range can be increased by applying magnetic coupling with
resonance phenomenon applied on. A magnetic field is
generated when electric charge moves through space or
within an electrical conductor. The geometric shapes of the
magnetic flux lines produced by moving charge (electric
current) are similar to the shapes of the flux lines in an
electrostatic field.