Middle-East Journal of Scientific Research 24 (4): 1283-1288, 2016
ISSN 1990-9233
© IDOSI Publications, 2016
DOI: 10.5829/idosi.mejsr.2016.24.04.23364
Analysis of Various Inductor Core Materials for Wireless Power Transfer
T. Rampradesh, R. Vignesh and A. Nivedha
Department of Electrical & Electronics Engineering, IFET College of Engineering, Tamil Nadu, India
Abstract: Wireless power transfer can make an extraordinary change in the field of electrical engineering, which
eliminates the use of conventional copper cables and current carrying wires. Here we introduce the basic
concepts of wireless power transfer using electromagnetic induction and compare the performance in terms of
temperature and electric field intensity of inductors with three different types of core materials such as air core,
ferrite core and iron core. The model was simulated using Ansys and Pro-e environment and a comparative
analysis is made using bar charts. Its future applications includecharging of mobiles, electrical vehicles, sensing
smoke, detecting gas, etc. It can also be used for certain remote applications.
Key words: Electrical energy
Energy transfer
Receiving stations
INTRODUCTION
The transfer of electrical energy from a power source
to an electric load without a direct physical connection
between them, usually via an electromagnetic field, is
defined as Wireless Power Transfer Technology (WPTT).
Nowadays electronic devices such as cell phones and
laptops need WPTT for wireless charging with the
advantage of protection from any faults at external power
source.
In the 1890’s, a Wireless Power Transfer (WPT)
system was demonstrated by Nikola Tesla using resonant
transformers called Tesla coils. In July 2007, a group of
researchers at MIT presented a method of transmitting
power wirelessly. The researchers used an
electromagnetically coupled resonance system to power
a 60W bulb wirelessly from a distance over two meters
away. The magnetic resonance coupling technology has
been found to be viable for midrange energy transfer. It is
used for charging the electric vehicles with energy
efficiency up to 90% in a relatively short time. It is also
used for low power wireless charging of mobile phones
with a power up to five watts and energy efficiency up to
70%.
The main research theme of all WPT technology is
looking for improving the transmission efficiency and the
distance between the transmitter and the receiving
stations. The inductor is usually a coil wrapped around a
core material. The efficiency of the inductor depends
Electric load
Magnetic resonance
upon the number of turns and the material used for the
core and the coil [1]. These parameters decide the
temperature and the electric field intensity of the inductor
which has a direct impact on the efficiency of the
inductor.
Concept of WPT Technology: The general concept of
WPT (Wireless power) [2, 3] is based upon the
principle of electromagnetic induction. The model
consists of a transmitter coil and a receiver coil.
The coils are inductors that are placed a suitable
distance. The transmitter coil is powered by a
generator or any power source as shown in Fig. 1. The
power in the transmitter coil is electromagnetically
coupled with the receiver coil which is placed at a
suitable distance [4]. Thus the receiver coil is energized
and wireless power transmission is achieved. Later the
power is rectified and regulated according to the load
conditions.
Transmitter and Receiver Side: Transmitter and receiver
coils are inductor coils which are used to transfer the
power over a specified distance. The power transfer is
done by the means of mutual induction [5, 6]. The
magnetic coupling is specified for some fixed distance.
This distance depends upon magnetic field of the coil
received by an air core receiver coil. Greater the magnetic
field, greater the distance over which the power is
transferred.
Corresponding Author: T. Rampradesh, Department of Electrical & Electronics Engineering,
IFET College of Engineering, Tamil Nadu, India.
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Fig. 1: Concept of WPT
Core Material Properties: Air core inductor is the type
where no solid core exists inside the coils. In addition, the
coils that wound on nonmagnetic materials such as
ceramic and plastic are also considered as air cored.
Calculation of the inductance to design air core inductor:
L= (d2 * n2)/ (18d+40 l)
(1)
where, L is inductance in micro Henrys,
d is coil diameter in inches,
l is coil length in inches and
n is number of turns.
Fig. 2: Transmitter side
Fig. 3: Receiver side
The high frequency alternating current, which is
linked with the wireless power transmitting coil (Fig. 2),
would create an alternating magnetic field in the coil due
to induction, to transmit energy. In the wireless power
receiver section, the receiver coils (Fig. 3) receives that
energy as an induced alternating voltage (due to
induction) in its coil [7, 8].
Iron Core Inductor: The inductance value on the air core
inductor depends on the number of spires (turns), length,
diameter, thickness of the spiral, etc. The air core
inductance range values are limited. In order to increase
the inductance value of an inductor, an iron core is placed
inside of it. This iron core has very special magnetic
characteristics. What they do is to reinforce the magnetic
field. The magnetism of the core material depends on the
bias of “the molecular magnetic domains”, when the
magnetic field that affects the inductor changes in a
continuous way.
These domains should be able to change its position
so that the core meets its goal. The magnetic domains may
or may not follow the magnetic field variations depending
on the material the core is made of. If the magnetic field
variation cannot be followed, the core is useless and the
molecular domains get disordered, leaving the core
magnetically unbiased.
Calculation of inductance to design iron core
inductor:
L= AL*N2
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(2)
Middle-East J. Sci. Res., 24 (4): 1283-1288, 2016
where, N is a number of turns
AL is inductance factor
Ferrite Core Inductor: Ferrites are one of the main core
materials used in inductors and transformers. Ferrite
inductor is used to provide an increase in the permeability
of the medium around the coil to increase the inductance
of the inductor. Ferrites are widely used within inductor
technology to improve the performance of the inductor.
Ferrites are basically iron based magnetic material in
the form of a ceramic. Ferrites are made from a powder and
can therefore be manufactured in a variety of shapes
according to the requirements.
L(nH) = AL*N2,
The inductor was designed with three different types
of core materials viz., air core, iron core and ferrite core.
All three inductors had a copper coil of 12 turns per coil.
The three inductors with different core materials were
simulated separately and the values of electric field
intensity and temperature for the three cases were
compared. The output results are shown in Fig. 4 to 9.
(3)
where, L is the inductance in nano henries,
N is the number of turns of wire in the coil wound
around the ferrite rod (centered on the rod), AL is the
“inductance factor” which describes the rods ability to
provide inductance. The AL values are in units of (nH/turn
squared) which are the same as AL values in units of
(mh/1000 turns). The inductance factor (AL) is not a
constant; it depends on the length of the coil. As the coil
length decreases, the value of AL increases.
Fig. 4: Air core – Electric Field Intensity
AL values
Number of turns =
desiredinductance (mH)
(1000) (mH/1000Turns)
A L value
Or
Number of turns =
A L value
desiredinductance(uh)
(100)A (uhy/100turns)
A L value
100

2
=
 (Lin uH)
 No.of.turns 
(4)
(5)
(uh/100turns)
(6)
2
 1000 
A L (uH/1000 turns) = 
 (Lin uH)
 Noof turns 
(7)
Simulation Result: The performance characteristics of
inductors, in terms of temperature and electric field
intensity are analyzed in Ansys and Pro-e environment.
ANSYS is a general purpose software, used to simulate
interactions of all disciplines of physics, structural,
vibration, fluid dynamics, heat transfer and
electromagnetic
for
engineers.Pro-eknown
as
Pro/ENGINEER is a parametric, integrated 3D
CAD/CAM/CAE solution created by Parametric
Technology Corporation (PTC).
Fig. 5: Ferrite core – Electric Field Intensity
Table 1: Simulation result of different type of core material
Core Material
Magnetic Field Intensity (V/m)
Temperature (w/m 3)
Air Core
0.0218
1914.5
Ferrite Core
5.812
4.906
Iron Core
0.0011
16.17
From Table 1 and Fig. 10 and 11 ferrite core has high
magnetic field intensity and less temperature rise. To
improve the efficiency and distance between the coils in
wireless power transfer, ferrite is the best core material to
design an inductor based on the above simulation results.
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Middle-East J. Sci. Res., 24 (4): 1283-1288, 2016
Fig. 6: Iron core – Electric Field Intensity
Fig. 7: Air core – Joule Heat
Fig. 8: Ferrite core – Joule Heat
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Middle-East J. Sci. Res., 24 (4): 1283-1288, 2016
Fig. 9: Iron core – Joule Heat
Fig. 10: Magnetic field intensity for different core materials
Fig. 11: Temperature for different core materials
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Middle-East J. Sci. Res., 24 (4): 1283-1288, 2016
Application
REFERENCES
Automatic wireless charging of mobile electronics,
home applicant.
Robots, packaging machinery, assembly machinery
and machine tools can take advantage of this
technology.
Direct wireless power for wireless sensors and
actuators, eliminates the need for expensive power
wiring or battery replacement and disposal.
1.
2.
3.
CONCLUSION
The main purpose of our proposed work was to
design a device that provides wireless transfer of power
at medium distance through inductive coupling. This
concept is an Emerging Technology and in coming years
the distance of power transfer and efficiency can be
enhanced as the research across the world is still going
on. Wireless power transfer can make a remarkable change
in the field of the electrical engineering which eliminates
the use of conventional copper cables and current
carrying wires. This will lead to no more messy wires and
with widespread enough use it could even eliminate
costly batteries. In charging of mobile via inductive
coupling is done where the distance was restricted to 5cm
but in our proposed work, we have increased the distance
to almost 10 inches by designing the inductor with core
material for high magnetic flux. Wireless technology will
be a key enabler for future smart applications.
4.
5.
6.
7.
8.
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