Wireless Power Transmission Project Report

A
Major Project
“Wireless Power Transmission”
Submitted the partial fulfillment for award the degree of
Bachelor of Technology
In
Electrical Engineering
From
Rajasthan Technical University, Kota
Session 2019 - 2020

Guided By Submitted By
Mr. Yogesh Verma Vipul Kumar Jangir
Department of Electrical Engg. Sumit Kumar
Sandeep Saini
Ranjeet Verma
Raju Lal Meena
Rajesh Jangid
Pradeep Dan
IV B.Tech. VIII Sem
Submitted to
Mr. Rahul Garg
Head of Department
Department of Eelectrical Engineering
MAHARISHI ARVIND INSTITUTE OF ENGINEERING &
TECHNOLOGY, JAIPUR

I
ACKNOWLEDGEMENT
We would like to express our gratitude and thanks to Maharishi Arvind Institute Of
Engineering & Technology, for providing an opportunity for fulfilling our most cherished
desire of reaching our goals and thus helping to pave a bright career for us.
We would like to sincerely thank our HOD and guide, Mr. Rahul Garg, Department of
Electrical Engineering, MAIET, for his encouragement, support and his valuable guidance
and input, and for helping us with the project and prepare the report for the same.
We also thank all the Faculty members and technical staff of the Department of Electrical
Engineering for their continued support and guidance and in helping us successfully complete
out project.
We would like to thank our parents and friends for extending for their hands directly or
indirectly at every juncture of need.

II
ABSTRACT
The transmission of electrical energy from source to load for a distance without any
conducting wire or cables is called Wireless Power Transmission. The concept of wireless
power transfer was realized by Nikola Tesla. Wireless power transfer can make a remarkable
change in the field of the electrical engineering which eliminates the use conventional copper
cables and current carrying wires. Day by day new technologies are making our life simpler.
Wireless charging through resonance could be one of the next technologies that bring the
future nearer. In this project it has been shown that it is possible to charge low power devices
wirelessly via inductive coupling. It minimizes the complexity that arises for the use of
conventional wire system. In addition, the project also opens up new possibilities of wireless
systems in our other daily life uses.
In this project we will try to achieve transmission of power through wireless technology. The
main application of this might be seen in the transmission of energy from satellite solar power
plants. The methods of transmitting power through wireless technology include RIC
(Resonant Inductive Coupling), microwave and laser transmission techniques. Our aim is to
develop a system for power transmission using one of the above techniques mainly RIC or
Microwave transmission.

IV
CHAPTER 1 INTRODUCTION ...................................................................................1
1.2 Field Regions: .......................................................................................................1
CHAPTER 2 LITERATURE SURVEY........................................................................4
2.2 Tesla’s Experiment: ..............................................................................................4
CHAPTER 3 OVERVIEW ............................................................................................5
CHAPTER 4 WITRICITY ............................................................................................7
4.1 What WiTricity is not?..........................................................................................7
4.2 What WiTricity is?................................................................................................9
4.3 Why WiTricity? ....................................................................................................9
4.4 Range: .................................................................................................................10
4.5 Evanescent Waves: .............................................................................................11
4.6 How it works:......................................................................................................11
CHAPTER 5 BASIC CONCEPT OF WIRELESS POWER TRANSFER .................14
5.1 Inductive Coupling..............................................................................................14
5.2 Inductive Charging..............................................................................................15

V
CHAPTER 6 INDUCTANCE OF COIL AND COIL DESIGN .................................16
6.3 Losses in coil: .....................................................................................................18
6.4 Block Diagram.......................................................................................................18
6.5 Circuit Diagram...................................................................................................19
6.6 Components used in transmitter: ........................................................................21
6.7 Components used in receiver:.............................................................................22
CHAPTER 7 TRANSMITTER ...................................................................................24
7.1 Working of transmitter circuit: ...........................................................................24
7.2 DC supply: ..........................................................................................................25
7.3 Oscillator circuit:.................................................................................................25
7.4 Working of oscillator circuit:..............................................................................25
7.5 Transmitter coil:..................................................................................................26
CHAPTER 8 RECEIVER............................................................................................27
8.1 Working of Receiver:..........................................................................................27
8.2 Receiver coil: ......................................................................................................28

VI
8.3 Rectifier:..............................................................................................................28
8.4 Operation of bridge rectifier: ..............................................................................28
8.5 Voltage regulator IC: ..........................................................................................29
8.6 Buck converter:...................................................................................................29
CHAPTER 9 PCB LAYOUT ......................................................................................30
9.1 Transmitter:.........................................................................................................30
9.2 Receiver: .............................................................................................................31
CHAPTER 10 WIRELESS POWER TRANSMISSION ............................................33
10.5 Far Field Methods:............................................................................................34
CHAPTER 11 MAGNETIC RESONANCE INDUCTION ........................................38
11.1 Resonant Induction: ..........................................................................................38
11.2 Terms related to Resonance:.............................................................................40
11.3 Implementation of MRI in our project:.............................................................42
CHAPTER 12 WIRELESS POWER TRANSMISSION USING
RESONANTINDUCTIVE COUPLING .....................................................................43
CHAPTER 13 OSCILLATOR DESIGN.....................................................................46

VII
CHAPTER 14 ANTENNA DESIGN ..........................................................................52
CHAPTER 15 FINAL ASSEMBLY ...........................................................................59
CHAPTER 16 RESULTS ............................................................................................67
CHAPTER 17 CONCLUSION....................................................................................71
CHAPTER 18 POSSIBLE APPLICATIONS AND FUTURE WORK ......................73
17.1 Applications:.....................................................................................................73
17.2 Future work:......................................................................................................73
CHAPTER 18 REFERENCES ....................................................................................75
CHAPTER 19 BIOGRAPHY………………………………………………………..58
APPENDIX…………………………………………………………………………..59

IX
LIST OF FIGURES
Figure 1: Single source coil powering multiple devices………………………………6
Figure 2: The ratio of the distance between the two objects…………………………..7
Figure 3: WiTricity circuit used to glow LED bulb…………………………………...8
Figure 4: Inductive Coupling with Four Component Fluxes………………………….9
Figure 5: Single Layer Coil…………………………………………………………11
Figure 6: Block Diagram……………………………………………………………..12
Figure 7: Circuit Diagram Of Transmitter…………………………………………..13
Figure 8: Circuit Diagram Of Receiver………………………………………………13
Figure 9: TRANSMITTER…………………………………………………………16
Figure 10: Block Diagram Of The Receiver Module…………………………….18
Figure 11: PCB Layout Of Transmitter……………………………………….20
Figure 12: PCB Layout Of Receiver…………………………………………..20
Figure 13: Comparison……………………………………………………………24

X
Figure 14: Block Diagram Of Wireless Power Transmission Using Resonant
Inductive Coupling…………………………………………………………………..28
Figure 15: Circuit Description Of Royer Oscillator………………………………31
Figure 16: Design Of Royer Oscillator…………………………………………….32
Figure 17: Coil Design 1………………………………………………………..35
Figure 18: Coil Design 2………………………………………………………….36
Figure 19: Coil Design 3………………………………………………………….37
Figure 20: High Frequency Converter 1…………………………………………..40
Figure 21: High Frequency Converter 2…………………………………………41
Figure 22: HF Converter Closed 1……………………………………………….42
Figure 23: HF Converter Closed 2………………………………………………..43
Figure 24: Transmission and Receiving coils …………………………44
Figure 25: CRO Waveforms At No Load Input………………………..45
Figure 26: CRO Waveforms At No Load O utput………………………46
Figure 27: CRO Waveforms At No Loaded Output……………………..47
F igur e 28 :P os s ib le Ap p lic a t io ns A nd F ut ur e W or k…… …… .48

XI
LIST OF TABLES
Table 1: Components used in transmitter……………………………………14
Table 2 : Components used in receiver……………………………………….15
Table 3 : Components are used to make the oscillator………………………33
Table 4 : Comparison of the designs…………………………………….38

1
CHAPTER 1 INTRODUCTION
1.1 HISTORY
Wireless power transfer (WPT) is the transmission of electrical power from a power source to
a consuming device without using discrete man made conductors. Researchers have
developed several techniques for moving electricity over long distance without wires. Some
exist only as theories or prototypes but others are already in use. This paper provides the
techniques used for wireless power transmission. It is a generic term that refers to a number of
different power transmission technologies that use time-varying electromagnetic fields.
Wireless transmission is useful to power electrical devices in case where interconnecting
wires are inconvenient, hazardous, or are not possible. For example the life of WSN is its
node which consists of several device controllers, memory, sensors, actuators, transceivers
and battery and battery. The transceiver can operate in four states,i.e.
1) Transmit
2) Receive
3) Idle and
4) Sleep.
The major energy problem of a transmitter of a node is its receiving in idle state, as in this
state it is always being ready to receive, consuming great amount of power. However, the
batter has a very short lifetime and moreover in some developments owing to both practically
and economically in feasible or may involve significant resists to human life. That is why
energy harvesting for WSN in replacement of battery is the only and unique solution. In
power by electromagnetic fields across an intervening space to one or more receiver devices,
where it is converted back to electric power and utilized. In communication the goal is the
transmission of information, so the amount of power reaching the receiver is unimportant as
long as it is enough that signal to noise ratio is high enough that the information can be
received intelligibly. In wireless communication technologies, generally, only tiny amounts of
power reach the receiver. By contrast, in wireless power, the amount of power received is the
important thing, so the efficiency (fraction of transmitted power that is received) is the more
significant parameter.
1.2 Field Regions:
Electric and magnetic fields are created by charge particles in matter such as electrons. A
stationary charge creates an electrostatic field in the space around it. A steady current of
charge (direct current, DC) creates a static magnetic field around it. The above fields contain
energy, but cannot carry power because they are static. However time-varying fields can carry
power. Accelerating electric charge, such as are found in an alternating current (AC) of

2
electrons in a wire, create time-varying electric and magnetic fields in the space around them.
These fields can exert oscillating force on the electrons in a receiving “antenna”, causing
them to move back and forth. These represent alternating current which can be used to power
a load. The oscillating electric and magnetic fields surrounding moving electric charges in an
antenna device can be divided into two regions, depending on distance. Range from the
antenna. Different technologies are used for transmitting power: Near-field or non-radiative
region- This means the area within about wavelength (λ) of the antenna.

3
1.3 Issues in WPT
One of the major issue in power system is the losses occurs during the transmission and
distribution of electrical power. As the demand increases day by day, the power generation
increases and the power loss is also increased. The major amount of power loss occurs during
transmission and distribution. The percentage of loss of power during the transmission and
distribution is approximated as 26%.
The main reason for power loss during transmission and distribution is the resistance of wires
used for grid. The efficiency of power transmission can be improved to certain level by using
high strength composite over head conductors and underground cables that use high
temperature super conductor. But, the transmission is still inefficient. According to World
Resources Institution (WRI), India’s electricity grid has the highest transmission and
distribution losses in the world a whopping 27%.Numbers published by various Indian
government agencies put that number at 30%, 40% and greater than 40%. This is attributed to
technical losses (grid’s inefficiencies) and theft. The above discussed problem can be solved
by choose an alternative option for power transmission which could provide much higher
efficiency, low transmission cost and avoid power theft. Microwave Power Transmission is
one of the promising technologies and may be the righteous alternative for efficient power
transmission.
1.4 Resonant Inductive Coupling
Resonance, such as resonant inductive coupling, can increase the coupling between the
antennas greatly, allowing efficient transmission at somewhat greater distance, although the
fields still decrease, although the fields still decrease exponentially. Therefore the range of
near-fields devices is conventionally divided into two categories: Short range- up to about one
antenna diameter: D range ≤ Dant. This is the range over which ordinary non-resonant
capacitive or inductive coupling can transfer particle amounts of power.
Mid-range-up to 10 times the antenna diameter: range ≤ 10 Dant. This is range over which
ordinary non-resonant capacitive or inductive coupling can transfer practical amount of power.
Far-field or radiative region: Beyond about 1 wavelength(λ) of antenna, the electric and
magnetic fields perpendicular to each other and propagate as an electromagnetic wave;
example are radio waves, microwave, or light waves. This part of the energy is radiative,
meaning it leaves the antenna whether or not there is a receiver absorbs it. The portion of
energy which does not strike the receiving antenna is dissipated and lost to the system. The
amount of power emitted as electromagnetic waves by an antenna depends on the ratio of the
antenna’s size Dant to the wavelength of waves λ, which is determined by the frequency f
where the frequency: λ=c/f. At low frequencies f where the antenna is much smaller than the
size of the waves, Dant << λ, very little power is radiated. Therefore the near-field devices
above, which use lower frequencies, radiate almost none of their energy as electromagnetic
radiation. Antennas about the same size as the wavelength Dant ≈ λ such as mono pole or
dipole antennas radiate power efficiently, but the electromagnetic waves are radiated in all
directions. So if the receiving antenna is far away, only a small amount of the radiation will

4
hit it. Therefore, these can be used for shorter range inefficient power transmission but not for
short range transmission but for long range transmission. However, unlike fields,
electromagnetic radiation can be focused by reflection or refraction into beams. By using a
high gain antenna or optical system which concentrates the radiation into a narrow beam
aimed at the receiver, it can be used for long range power transmission. From the Rayleigh
criterion, to produce the necessary to focus a significant amount of the energy on a distant
receiver, an antenna must be much larger than the wavelength of the wave used Dant >> λ =
c/f. Practical beam power devices require wavelength in the centimetre region or below in the
corresponding to frequencies above 1GHz , in themicrowave range.
CHAPTER 2 LITERATURE SURVEY
2.1 HISTORY
In 1826 Andre-Marie Ampere developed ampere’s circuital law showing that electric current
produces a magnetic field. Michael Faraday developed Faraday’s law of induction in 1831,
describing the electromagnetic force induced in a conductor by a time-varying magnetic flux.
In 1862 James Clerk Maxwell synthesized these and other observations, experiments and
equations of electricity, magnetism and optics into a consistent theory, deriving Maxwell’s
equations. This set of partial differential equations forms the basis for modern
electromagnetic including the wireless transmission of electrical energy.
2.2 Tesla’s Experiment:
Tesla was demonstrating wireless power transmission in a lecture at Columbia
College, New York, in 1891. The two metal sheets are connected to his Tesla coil
oscillator, which applies a high frequency oscillating voltage. The oscillating electric
fields between the sheets ionizes the low pressure gas in the two long Geissler tubes
he is holding, causing them to glow by fluorescence, similar to neon lights.
Experiment in resonant inductive transfer by Tesla at Colorado Springs 1899.The coil
is in resonance with Tesla’s magnifying transmitter nearby, powering the light bulb at
bottom. Inventor Nikola Tesla performed the first experiments in wireless power
transmission in wireless power transmission at the turn of the 20th century, and may
have done more to popularize the idea than any other individual. In the period 1891 to
1904 he experimented with transmitting power by inductive and capacitive coupling
using spark-excited radio frequency resonant transformer, now Called Tesla coils,
which generated high AC voltages. With these he was able to transmit power for short
distances without wires. In demonstrations before the American Institute of Electrical
Engineers and the 1893 Columbian Exposition in Chicago he lit light bulbs from
across a stage. He found he could increase the distance by using a receiving LC circuit
tuned to resonance with the transmitter’s LC circuit, using resonant inductive

5
coupling. At his Colorado springs laboratory during 1899-1900, by using voltages of
the order of 10 mega volts generated by an enormous coil. He was able to light three
incandescent lamps at a distance of a about one hundred feet. The resonant inductive
coupling which Tesla pioneered is now a familiar technology used throughout
electronics and is currently being widely applied to short-range wireless power
systems.
CHAPTER 3 OVERVIEW
3.1 Advantages
It makes devices more convenient and thus more desirable to purchasers, by eliminating the
need for a power cord or battery replacement. · The power failure due to short circuit and
fault on cables would never exist in transmission. · Reduction of e-waste by eliminating the
need of power cords. · Wireless charging offers no corrosion as the electronics are all
enclosed, away from water or oxygen in the atmosphere.
3.2 Disadvantages
The capital cost for particle implementation of WPT seems very high. · WPT may cause
interference with present communication systems. · Less efficiency compared to traditional
charging.

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3.3 Biological Impacts
Common beliefs fear the effect of microwave radiation. But the studies proven that the
microwave radiation level would be never higher than the dose received while opening the
microwave oven door, meaning it slightly higher.
3.4 Applications
WPT finds its applications in a various fields. It can be used in moving targets such as fuel
free airplanes, fuel free electric vehicles, moving robots and fuel free rackets, automatic
wireless charging for mobile robots, cordless tools and instrument which eliminates complex
mechanisms, and labour intensive manual recharging and battery replacement. · Another
application of WPT is solar power satellites, energy to remote areas, broadcast energy
globally. WPT are used for Ubiquitous power source, RF Power Adaptive Rectifying Circuits
(PARC).
3.5 Future Scope
Witricity is building a near field wireless charging apparatus for consumer devices with the
help of the Haier group, a Chinese electronics manufacturer. Witricity demonstrated this
technology by wireless powering a 32 inch television at a distance of six feet. Delphi
Automotives is working with Witricity to develop a wireless charging system for electric cars.
The groundbreaking technology will enable to automotive manufacturer to integrate wireless
charging into the design of hybrid & electric vehicles. There is another standard protocol for
charging mobile phone initiated by the Wireless Power Consortium.

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CHAPTER 4 WITRICITY
4.1 What WiTricity is not?
4.1.1 Traditional Magnetic Induction:
Though WiTricity looks like traditional magnetic induction, it is not the same. In the
traditional magnetic induction system, conductive coils transmit power to each other
wirelessly over very short distances. In this system two coils must be very close to each other
and may even overlap. “The efficiency of power transfer drops by orders of magnitude when
distance between the coils becomes larger than their sizes”. Examples of traditional magnetic
induction power exchange are electronic toothbrushes, charging pads, etc.
4.1.2 Radioactive Power Transfer:
To facilitate transfer of information over a wide spectrum to multiple users, radio frequency
energy is broadcasted through radiation. Each radio or wireless receiver unit needsto have an
amplifier section with external power supply so as to receive the information. Radio
transmission is capable of low power information transfer, but ineffective in case of power
transfer as most of the power is lost in free space due to radiation. Other alternatives of power
transfer such as feeding more power into the transmitters or using directed radiations using
antennas cause high risk of interference with other radio frequency devices and also pose a
safety hazard for living organisms which come in between the line-of-sight of the transmitter
and the receiver. These limitations make radio transmission an impractical means of wireless
power transfer for consumer, commercial, or any industrial application.
The other means of wireless power transfer include visible and invisible light waves such as
sun rays, laser beams, etc. The sun being an excellent source of light energy, extensive
research is being carried out to capture this energy and convert it to electrical energy using
photovoltaic cells. A collimated beam of laser rays can be used to transfer energy in a targeted
way. But it requires a clear line-of-sight between the transmitter and the receiver to insure
safe and efficient transmission.
4.1.3 MRI:

8
MRI stands for Magnetic Resonance Imaging used to develop diagnostic images of soft
tissues in the human body. It cannot be compared with WiTricity, i.e., Resonant Magnetic
Coupling as they both have contrasting principles. The procedure of MRI makes use of a
strong DC magnet which orients the magnetic fields of atoms present in the human tissues
and also affects the radio frequency fields so as to manipulate those atoms in a desired way to
obtain clear images of the tissue structure.

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4.2 What WiTricity is?
The term WiTricity is a blend of the words ‘wireless’ and ‘electricity’. It is a form of non
radiative power transfer. Most of the other techniques discussed above use radiative forms of
power transfer. WiTricity is different as it uses magnetic coupling. In this a clear line of sight
between the emitter and receiver is not needed. WiTricity is also a safe mode of power
transfer as the interaction between the magnetic fields and biological organisms is not
hazardous.
These attributes make WiTricity a form of potential technology which can be used to transfer
electricity/power between electrical sources and receivers without the use of wires or cables.
Keeping certain factors in mind and also ensuring that the electromagnetic field is strong
enough to allow reasonable power transfer, it is possible to transfer power over a certain
amount of distance. “This is possible if both the emitter and the receiver achieve magnetic
resonance”. Wireless transmission of energy is very helpful in areas where uninterrupted and
instantaneous power is required and using wires inconvenient, hazardous, or impossible.
4.3 Why WiTricity?
Imagine a world in which you do not require the use of any kinds of cords to power or charge
your electronic devices. Everything from your lamp to your cell phone and even your
television set can be charged or powered without cords. This can be made possible with the
use of WiTricity. Centuries ago, scientists would have laughed at the idea of wireless
communication, but today we cannot imagine a world without cell phones and the internet.
The rapid growth and development in the research of wireless technology has helped the
world think out of the box. Now it is time for the world to think even further and explore the
world of electronics which can be powered wirelessly through the technology provided by
WiTricity. By using a single source coil, multiple devices with receiving coil can be powered.
With widespread use it could even eliminate costly batteries and there will be no more messy
wires.

10
Figure 1: Single source coil powering multiple devices
4.4 Range:
WiTricity technology is designed for “mid-range” distances, which we consider to be
anywhere from a centimeter to several meters. The actual operating range for a given
application is determined by many factors, including power source and capture device sizes,
desired efficiency, and the amount of power to be transferred.
As shown below, the ratio of the distance between the two objects and their radius
increases, the ratio of coupling coefficient and resonance widths decreases.

11
Figure 2: The ratio of the distance between the two objects
Here the ratio of coupling coefficient and resonance width represents efficiency. Using
different materials will allow us to have less loss at a better distance/radius ratio, because as
per equations permittivity of medium is also an important factor.
4.5 Evanescent Waves:
A near field standing wave whose intensity decays exponentially as it travels a distance from
the point of its origin is called as an evanescent wave. These waves obey the property of
general wave equations. They are originated at the boundary between two media having
different wave motion properties and their intensity is maximum within one-third of a
wavelength from the surface of occurrence. Evanescent waves are observed in areas of
electromagnetic radiation, quantum mechanics, acoustics and string waves.
In the field of optics and acoustics, when the waves traveling in a medium strike the boundary
at an angle greater than the critical angle, they undergo total internal reflection which gives
rise to evanescent waves. Physically, since the electric and magnetic fields are continuous at a
boundary of the medium, the evanescent waves are generated. Similarly, in the case of
quantum mechanics, the particle motion which is represented by the Schrödinger
wave-function is normal to the boundary and is continuous.
4.6 How it works:

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The most simple and common example of acoustic resonance is shattering of a wine glass by
an opera singer. When identical wine glasses are filled with different quantity of wine, they
each have different resonance frequencies. Now, when an opera singer sings and a certain
voice pitch matches the resonant frequency of a specific glass, the acoustic energy
accumulated by the glass is sufficient for it to explode, while other glasses remain unaffected.
Thus, there exists a strongly coupled regime in all systems of coupled resonators and highly
efficient energy transfer is achieved when operated in this regime.
Since WiTrcity operates in a non-radiative field, there is an advantage that even if the
receiving coil does not pick up all the power, the residual power remains in the vicinity of the
sending coil and is not lost in the environment due to radiation. The WiTricity circuit is
designed in a way that the frequency of the alternating current is increased to the resonant
frequency. The travelling current induces magnetic and electric fields in the inductor and
capacitor loops respectively which extends up to 5 meters around the device. This magnetic
field induces an electric current in the inductor loop of any mobile gadget having the receiver
coil with the same resonant frequency. Thus both the circuits resonate together and energy
transfer is achieved.
Figure 3: WiTricity circuit used to glow LED bulb.
The above circuit is a good example of the WiTricity system. As can be seen from the
diagram, it uses two coils which are tuned at the same resonant frequency. The main supply is
given to transformer which induces high frequency AC on the primary coil. When secondary
coil comes in the vicinity of the primary coil, power gets transferred from primary to
secondary. Power transfer takes place as high frequency gets induced on the secondary coil.
The signal at the secondary coil is rectified and given to the load.

13
Something the MIT team realized is that if evanescent tails (tails of energy) are made larger
than the size of the objects, energy could be conserved and energy lost due to radiation will be
less. This is something that they did differently from many previous tests, because most of the
time, long evanescent tails lead to higher interference between the devices.

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CHAPTER 5 BASIC CONCEPT OF WIRELESS POWER
TRANSFER
5.1 Inductive Coupling
Inductive or Magnetic coupling works on the principle of electromagnetism. When a wire is
proximity to a magnetic field, it generates a magnetic field in that wire. Transferring energy
between wires through magnetic fields is inductive coupling.
If a portion of the magnetic flux established by one circuit interlinks with the second circuit,
then two circuits are coupled magnetically and the energy may be transferred from one circuit
to the another circuit.
This energy transfer is performed by the transfer of the magnetic field which is common to
the both circuits.
In electrical engineering, two conductors are referred to as mutual-inductively coupled or
magnetically coupled when they are configured such that change in current flow through one
wire induces a voltage across the end of the other wire through electromagnetic induction.
The amount of inductive coupling between two conductors is measured by their mutual
inductance.
Figure 4: Inductive Coupling with Four Component Fluxes

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Power transfer efficiency of inductive coupling can be increased by increasing the number of
turns in the coil, the strength of the current, the area of cross-section of the coil and the
strength of the radial magnetic field. Magnetic fields decay quickly, making inductive
coupling effective at a very short range.
5.2 Inductive Charging
Inductive charging uses the electromagnetic field to transfer energy between two objects. A
charging station sends energy through inductive coupling to an electrical device, which stores
the energy in the batteries. Because there is a small gap between the two coils, inductive
charging is one kind of short distance wireless energy transfer.
Induction chargers typically use an induction coil to create an alternating electromagnetic
field from within a charging base station, and a second induction coil in the portable device
takes power from the electromagnetic field and converts it back into electrical current to
charge the battery. The two induction coils in proximity combine to form an electrical
transformer. Greater distances can be achieved when the inductive charging system uses
resonant inductive coupling.

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CHAPTER 6 INDUCTANCE OF COIL AND COIL DESIGN

17
6.1 Introduction
An ideal inductor has inductance, but no resistance or capacitance, and does not dissipate or
radiate energy. However, real inductors have resistance (due to the resistance of the wire and
losses in core material), and parasitic capacitance (due to the electric field between the turns
of wire which are at slightly different potentials). At high frequencies the capacitance begins
to affect the inductor's behavior; at some frequency, real inductors behave as resonant circuits,
becoming self-resonant. At frequencies above this the capacitive reactance becomes the
dominant part of the impedance. Energy is dissipated by the resistance of the wire, and by any
losses in the magnetic core due to hysteresis. At high currents, iron core inductors also show
gradual departure from ideal behavior due to nonlinearity caused by magnetic saturation. At
higher frequencies, resistance and resistive losses in inductors grow due to skin effect in the
inductor's winding wires. Core losses also contribute to inductor losses at higher frequencies.
6.2 Single Layer Coil
Figure 5: Single Layer Coil
A single layer coil, as shown in figure, has two advantages. Firstly, like all air core coils, it is
free from iron losses and the non-linearity mentioned above. Secondly, single layer coils have
the additional advantage of low self-capacitance and thus high self-resonant frequency.
In the simple case of a single layer solenoidal coil the inductance may be calculated as
follows:

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Where L is the inductance, d is the coil diameter in meters, l is the coil length in meters and n
is the number of turns.
6.3 Losses in coil:
At high frequencies, particularly radio frequencies (RF), inductors have higher resistance and
other losses. In addition to causing power loss, in resonant circuits this can reduce the Q
factor of the circuit, broadening the bandwidth. In RF inductors, which are mostly air core
types, specialized construction techniques are used to minimize these losses. The losses are
due to these effects:
I. Skin effect: The resistance of a wire to high frequency current is higher than its resistance
to direct current because of skin effect. Radio frequency alternating current does not penetrate
far into the body of a conductor but travels along its surface. Therefore, in a solid wire, most
of the cross sectional area of the wire is not used to conduct the current, which is in a narrow
annulus on the surface. This effect increases the resistance of the wire in the coil, which may
already have a relatively high resistance due to its length and small diameter.
II. Parasitic capacitance: The capacitance between individual wire turns of the coil, called
parasitic capacitance, does not cause energy losses but can change the behavior of the coil.
Each turn of the coil is at a slightly different potential, so the electric field between
neighboring turns stores charge on the wire. So the coil acts as if it has a capacitor in parallel
with it. At a high enough frequency this capacitance can resonate with the inductance of the
coil forming a tuned circuit, causing the coil to become self resonant.
6.4 Block Diagram

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Figure 6: Block Diagram
6.5 Circuit Diagram

20
Figure 7: Circuit Diagram Of Transmitter
Figure 8: Circuit Diagram Of Receiver

21
6.6 Components used in transmitter:
Table 1 : Components used in transmitter
Component’s Name Component’s Value Or Code
Voltage Source, Vdc 15V
Capacitor, C 10nF
Resistor, R1 39 ohm, 5watt
Resistor, R5 5.6k ohm

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Resistor, R6 5.6k ohm
Diode, D1 1N4148
Diode, D2 1N4148
MOSFET,Q1 IRF540
MOSFET, Q2 IRF540
Radio Frequency Choke,L1 120 µH
Radio Frequency Choke, L2 120 µH
Transmitter coil, L 8 µH
6.7 Components used in receiver:
Table 2 : Components used in receiver
Component’s Name Component’s Value or code

23
Diode, D1 OA79
Diode, D2 OA79
Diode, D3 OA79
Diode, D4 OA79
Capacitor, C1 10 Nf
Capacitor, C2 100 µF
Voltage Regulator IC IC LM 7812
Receiver coil, L 8 µH

24
CHAPTER 7 TRANSMITTER
7.1 Working of transmitter circuit:
The transmitter module of our project is made up of a D.C. power source, an oscillator circuit
(commonly known as an inverter) and a transmitter coil.
The D.C. power source provides a constant D.C. voltage to the input of the oscillator circuit.
There, this D.C. power is converted to a high frequency A.C. power and is supplied to the
transmitter coil. The transmitter coil, energized by the high frequency A.C. current, produces
an alternating magnetic
field.

25
Figure 9: TRANSMITTER
7.2 DC supply:
The D.C. Power Source consists of a simple step down transformer and a rectifier circuit. The
transformer steps down the voltage to a desired level and the rectifier circuit convert the A.C.
voltage to D.C.
7.3 Oscillator circuit:
The prototype oscillator Circuit designed for the project is a modified Royer oscillator. This
oscillator circuit is incredibly simple yet a very powerful design. Very high oscillating current
can be achieved with this circuit depending on the semiconductor used. Here high current is
necessary to increase the strength of the magnetic field.
7.4 Working of oscillator circuit:
The circuit consists of with two chokes labeled L1 and L2, two semiconductors (Here
N-channel Enhancement power-MOSFETS) labeled Q1 and Q2, a resonating capacitor
labeled C2 and an inductor (here the transmitter coil) labeled L3. Cross-coupled feedback is
provided via the diodes D1 and D2. R1, R3 and R2, R4 are the biasing network for
MOSFETS.
When power is applied, DC current flows through the two sides of the coil and to the
transistors’ drain. At the same time the voltage appears on both gates and starts to turn the
transistors on. One transistor is invariably a little faster than the other and will turn on more.
The current would continue to increase until the coil (transformer) saturates. The resonating
capacitor C causes the voltage across the primary to first rise and then fall in a standard sine
wave pattern.

26
Assuming that Q1 turned on first, the voltage at the drain of Q1’s will be clamped to near
ground while the voltage at Q2’s drain rises to a peak and then falls as the tank formed by the
capacitor and the coil primary oscillator through one half cycle. After that, D1 will be forward
bias by more voltage than D2 and hence it will turn on Q2 and cycle repeats.
The oscillator runs at the frequency determined by the inductance of the coil, the capacitor
value and to a lesser extent, the load applied to the secondary (Source coil). The operating
frequency is the familiar formula for resonance,
F= 1/2 × π × √(LC)
7.5 Transmitter coil:
For this project the transmitter coil was constructed with 92 mm diameter, 17 swg copper
wire and 7 turns.
From the equation of inductance of a single layer air core coil, we get inductance L = 8.1 uH.

27
CHAPTER 8 RECEIVER
8.1 Working of Receiver:
The receiver module of our project is made up of a receiver coil, a rectifier circuit and a
voltage regulator IC. And additional buck converter to get more current by decreasing output
voltage to 5 volt.
An A.C. voltage is induced in the receiver coil. The rectifier circuit converts it to D.C. and the
voltage regulator IC helps to maintain a constant limited voltage at the load.
The following block diagram gives a general idea of the receiver module:

28
Figure 10: Block Diagram Of The Receiver Module
8.2 Receivercoil:
Receiver coil for our project is designed same as transmitter coil with same value.
8.3 Rectifier:
A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration
that provides the same polarity of output for either polarity of input. When used in its most
common application, for conversion of an alternating current (AC) input into direct current a
(DC) output, it is known as a bridge rectifier. The essential feature of a diode bridge is that
the polarity of the output is the same regardless of the polarity at the input.
8.4 Operation of bridge rectifier:
During the Positive half cycle of the input AC waveform diodes D1 and D3 are forward
biased and D2 and D4 are reverse biased. When the voltage, more than the threshold level of
the diodes D1 and D3, starts conducting – the load current starts flowing through it.During the
negative half cycle of the input AC waveform, the diodes D2 and D4 are forward biased, and
D1 and D3 are reverse biased. Load current starts flowing through the D2 and D4 diodes.
Further we can use capacitor filter to remove ripples present in output of bridge rectifier.
After capacitor filter, smooth DC voltage is present at the input of voltage regulator.

29
8.5 Voltage regulator IC:
A voltage regulator is an electrical regulator designed to automatically maintain a constant
voltage level. It may use an electromechanical mechanism, or electronic components.
Depending on the design, it may be used to regulate one or moreAC or DC voltages. In this
project, LM 7812 voltage regulator IC is used since it allowed no more than 12v to the output.
8.6 Buck converter:
It is totally optional part in receiver circuit. It is used here to increase current at output. Buck
converter is DC to DC converter which step down the voltage and according to it, it increase
output current. Efficiency of converter is high (near about 98%) and hence very small amount of
power loss in this module.

30
CHAPTER 9 PCB LAYOUT
9.1 Transmitter:

31
Figure 11: PCB Layout Of Transmitter
9.2 Receiver:
Figure 12: PCB Layout Of Receiver

33
CHAPTER 10 WIRELESS POWER TRANSMISSION
10.1 Needfor WPT
Wireless power transfer (WPT) is the transmission of electrical energy from a power source
to an electrical load, such as an electrical power grid or a consuming device, without the use
of discrete man-made conductors.
Wireless transmission is useful to power electrical devices in cases where interconnecting
wires are inconvenient, hazardous, or are not possible.
10.2 Different methods for WPT
Wireless power techniques fall into two Categories:
1. Non- Radiative or Near Field Method
2. Radiative or Far Field Method
10.3 Near Field Method
In non-radiative techniques, power is typically transferred by magnetic fields using magnetic
inductive coupling between coils of wire. Applications of this type include electric toothbrush
chargers, RFID tags, smart cards, and chargers for implantable medical devices like artificial
cardiac pacemakers.
10.4 Resonance Induction and other Methods
Resonant inductive coupling or Electrodynamic induction is the near field wireless
transmission of electrical energy between two magnetically coupled coils that are part
of resonant circuits tuned to resonate at the same frequency. This process occurs in a

34
resonant transformer, an electrical component which consists of two high Q coils
wound on the same core with capacitors connected across the windings to make two
coupled LC circuits.
Resonant transformers are widely used in radio circuits as band pass filters, and in switching
power supplies. Resonant inductive coupling is also being used in wireless power systems.
We will discuss about Resonance in detail in further Chapters.
10.5 Far Field Methods:
In Radiative or far-field techniques, also called power beaming, power is transferred by
beams of electromagnetic radiation, like microwaves or laser beams. These techniques can
transport energy longer distances but must be aimed at the receiver. Proposed applications for
this type are solar power satellites, and wireless powered drone aircraft.
Wireless power uses the same fields and waves as wireless communication devices like radio,
another familiar technology that involves electrical energy transmitted without wires by
electromagnetic fields, used in cell phones, radio and television broadcasting, and Wi-Fi.
Far field methods achieve longer ranges, often multiple kilometer ranges, where the
distance is much greater than the diameter of the device(s).
10.6 Microwave

35
Microwaves are a form of electromagnetic radiation with wavelengths ranging from one
meter to one millimeter; with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm).
Power transmission via radio waves can be made more directional, allowing longer distance
power beaming, with shorter wavelengths of electromagnetic radiation, typically in the
microwave range. A rectenna may be used to convert the microwave energy back into
electricity. Rectenna conversion efficiencies exceeding 95% have been realized. Power
beaming using microwaves has been proposed for the transmission of energy from orbiting
solar power satellites to Earth and the beaming of power to spacecraft leaving orbit has been
considered.
Power beaming by microwaves has the difficulty that, for most space applications, the
required aperture sizes are very large due to diffraction limiting antenna directionality.
Power beaming by microwaves has the difficulty that, for most space applications, the
required aperture sizes are very large due to diffraction limiting antenna directionality. For
example, the 1978 NASA Study of solar power satellites required a 1-km diameter
transmitting antenna and a 10 km diameter receiving rectenna for a microwave beam at 2.45
GHz. These sizes can be somewhat decreased by using shorter wavelengths, although short
wavelengths may have difficulties with atmospheric absorption and beam blockage by rain or
water droplets.
Wireless high power transmission using microwaves is well proven. Experiments in the tens
of kilowatts have been performed at Goldstone in California in 1975 and more recently (1997)
at Grand Bassin on Reunion Island. These methods achieve distances on the order of
kilometer. Under experimental conditions, microwave conversion efficiency was measured to
be around 54%.
10.7 Lasers and other Methods

36
In the case of electromagnetic radiation closer to the visible region of the spectrum, power
can be transmitted by converting electricity into a laser beam that is then pointed at a
photovoltaic cell. This mechanism is generally known as 'power beaming' because the power
is beamed at a receiver that can convert it to electrical energy. At the receiver, special
photovoltaic laser power converters which are optimized for monochromatic light conversion
are applied.
 Advantages compared to other wireless methods are:
 Collimated monochromatic wavefront propagation allows narrow beam cross-section
area for transmission over large distances.
 Compact size: solid state lasers fit into small products.
 No radio-frequency interference to existing radio communication such as Wi-Fi and cell
phones.
 Access control: only receivers hit by the laser receive power.
 Drawbacks include:
 Laser radiation is hazardous. Low power levels can blind humans and other animals.
High power levels can kill through localized spot heating.
 Conversion between electricity and light is limited. Photovoltaic cells achieve 40%–50%
efficiency. (Note that the conversion efficiency of laser light into electricity is much
higher than that of sun light into electricity using solar cells).
 Atmospheric absorption, and absorption and scattering by clouds, fog, rain, etc., cause up
to 100% losses.
 Requires a direct line of sight with the target.

37
Laser 'power-beaming' technology was explored in military weapons and aerospace
applications. Also, it is applied for powering of various kinds of sensors in industrial
environment. Lately, it is developed for powering commercial and consumer electronics.
Wireless energy transfer systems using lasers for consumer space have to satisfy laser safety
requirements standardized under IEC 60825.
10.8 Comparison
Figure 13: Comparison

38
CHAPTER 11 MAGNETIC RESONANCE INDUCTION
11.1 Resonant Induction:

39
Resonant inductive coupling or electrodynamic induction is the near field wireless
transmission of electrical energy between two magnetically coupled coils that are part of
resonant circuits tuned to resonate at the same frequency. This process occurs in a resonant
transformer, an electrical component which consists of two high Q coils wound on the same
core with capacitors connected across the windings to make two coupled LC circuits.
Resonant transformers are widely used in radio circuits as band pass filters, and in switching
power supplies.
Resonant transfer works by making a coil ring with an oscillating current. This generates an
oscillating magnetic field. Because the coil is highly resonant, any energy placed in the coil
dies away relatively slowly over very many cycles; but if a second coil is brought near it, the
coil can pick up most of the energy before it is lost, even if it is some distance away. The
fields used are predominantly non-radiative, near fields , as all hardware is kept well within
the 1/4 wavelength distance they radiate little energy from the transmitter to infinity.
Non-resonant coupled inductors, such as typical transformers, work on the principle of a
primary coil generating a magnetic field and a secondary coil subtending as much as possible
of that field so that the power passing through the secondary is as close as possible to that of
the primary. This requirement that the field be covered by the secondary results in very short
range and usually requires a magnetic core. Over greater distances the non-resonant induction
method is highly inefficient and wastes the vast majority of the energy in resistive losses of
the primary coil.
Using resonance can help improve efficiency dramatically. If resonant coupling is used, each
coil is capacitively loaded so as to form a tuned LC circuit. If the primary and secondary coils
are resonant at a common frequency, it turns out that significant power may be transmitted
between the coils over a range of a few times the coil diameters at reasonable efficiency.
One of the applications of the resonant transformer is for the CCFL inverter. Another
application of the resonant transformer is to couple between stages of a super heterodyne
receiver.

40
11.2 Terms related to Resonance:
11.2.1 Coupling coefficient:
k is the coupling coefficient, Le1 and Le2 is the Leakage inductance.
The coupling coefficient is the fraction of the flux of the primary that cuts the secondary coil,
and is a function of the geometry of the system. The coupling coefficient, k, is between 0 and
1.
Systems are said to be tightly coupled, loosely coupled, critically coupled or over coupled.
Tight coupling is when the coupling coefficient is around 1 as with conventional iron-core
transformers. Over coupling is when the secondary coil is so close that it tends to collapse the
primary's field, and critical coupling is when the transfer in the pass band is optimal. Loose
coupling is when the coils are distant from each other, so that most of the flux misses the
secondary. In Tesla coils around 0.2 is used, and at greater distances, for example for
inductive wireless power transmission, it may be lower than 0.01.
11.2.2 Energy transfer and efficiency:
The general principle is that if a given oscillating amount of energy is placed into a primary
coil which is capacitively loaded, the coil will 'ring', and form an oscillating magnetic field.
The energy will transfer back and forth between the magnetic field in the inductor and the
electric field across the capacitor at the resonant frequency. This oscillation will die away at a
rate determined by the gain-bandwidth (Q factor), mainly due to resistive and radiative losses.
However, provided the secondary coil cuts enough of the field that it absorbs more energy
than is lost in each cycle of the primary, then most of the energy can still be transferred.

41
The primary coil forms a series RLC circuit, and the Q factor for such a coil is:
Q= (1/R)sqrt(L/C).
Because the Q factor can be very high, (experimentally around a thousand has been
demonstrated with air cored coils) only a small percentage of the field has to be coupled from
one coil to the other to achieve high efficiency, even though the field dies quickly with
distance from a coil, the primary and secondary can be severaldiameters apart.
It can be shown that a figure of merit for the efficiency is:
U=k*sqrt(Q1*Q2)
Where Q1 and Q2 are the Q factors of the source and receiver coils respectively, and k is the
coupling coefficient described above.
11.2.3 Power transfer:
Because the Q can be very high, even when low power is fed into the transmitter coil, a
relatively intense field builds up over multiple cycles, which increases the power that can be
received—at resonance far more power is in the oscillating field than is being fed into the coil,
and the receiver coil receives a percentage of that.
11.2.4 Voltage gain:

42
The voltage gain of resonantly coupled coils is directly proportional to the square root of the
ratio of secondary and primary inductances.
A=k*sqrt(L2/L1)
11.2.5 Transmitter coils and circuitry:
Unlike the multiple-layer secondary of a non-resonant transformer, coils for this purpose are
often single layer solenoids (to minimize skin effect and give improved Q) in parallel with a
suitable capacitor, or they may be other shapes such as wavewound litz wire. Insulation is
either absent, with spacers, or low permittivity, low loss materials such as silk to minimize
dielectric losses.
To progressively feed energy/power into the primary coil with each cycle,different circuits
can be used. One circuit employs a Colpitts oscillator.
11.3 Implementation of MRI in our project:
In our project we use the principle of Induction for the transfer of power from the primary to
the secondary coil. By using only Induction one cannot get a good stable power at the receiver
end so we use the principle of Resonant Magnetic Induction.

43
CHAPTER 12 WIRELESS POWER TRANSMISSION USING
RESONANTINDUCTIVE COUPLING
12.1 Introduction
Previous work in this field has indicated that wireless power transmission between two
inductively coupled coils has poor range and efficiency. This is standard inductive coupling
which results in low power efficiency (<30%) and large coils since most of the flux is not
linked between the coils. The resonance of an inductively coupled system increases the
amount of magnetic flux linked between coils and improves the power transmission
significantly. In this project, we will introduce wireless power transfer using resonant
inductive coupling to increase power transfer efficiency and density with smaller coils.
We use two coils, transmitting coil and receiving coil that are tuned to resonate at a particular
frequency so that the power transmission improves significantly. In this project we have used
a Royer Oscillator and a variable capacitor to tune the circuit.
12.2 Block Diagram

44
Figure 14: Block Diagram Of Wireless Power Transmission Using Resonant Inductive
Coupling
12.3 Basic Components
12.3.1 Step-down Transformer:
Supply is taken from a normal 220V, 50Hz single phase socket and fed to the step down
transformer. It has a current rating of 2A. Here, we have stepped down the voltage from 220V
AC to 12V AC.
12.3.2 Bridge Rectifier :

45
The output from the transformer is rectified using a Bridge Rectifier module. At the output we
get a 12V unregulated DC output.
12.3.3 Voltage Regulator:
We need to obtain a constant regulated DC voltage to supply the oscillator circuit. Hence we
have used a Buck Converter module. It is a DC-DC converter which gives a regulated DC
supply at the output.
12.3.4 Oscillator:
We need to get an oscillating signal at the transmitting coil. Hence we use a suitable oscillator
circuit to get a sinusoidal output. We have chosen Royer Oscillator circuit in our project.
12.3.5 Transmission & Receiving Coils:
We have used two coils which inductively coupled and their flux is linked with each other.
These behave like an air core transformer for the transmission of power. We have chosen
copper and aluminum coils of different sizes to find the optimum design for maximum power
transfer.
12.3.6 Output Rectification:
At the receiving end, we again use a Bridge Rectifier module to get a DC output from
the receiving coil. This DC output is unregulated. We hence use a Buck Converter to
get a constant rectified voltage. This regulated DC voltage is supplied to any kind of
DC load.

46
CHAPTER 13 OSCILLATOR DESIGN
13.1 Introduction
An electronic oscillator is a circuit that produces a periodic, oscillating electronic signal, often
a sine wave or a square wave. Oscillators convert direct current (DC) from a power supply to
an alternating current (AC) signal. They are widely used in many electronic devices. Common
examples of signals generated by oscillators include signals broadcast by radio and television,
clock signals that regulate computers and quartz clock, and the sounds produced by electronic
beepers and video games.
Oscillators are often characterized by the frequency of their output signal:
 A low frequency oscillator (LFO) is an electronic oscillator that generates a frequency
below ≈20 Hz. This term is typically used in the field of audio synthesizers, to
distinguish it from an audio frequency oscillator.
 An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz.
 An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to
100 GHz.
In this project we will be using a class of oscillator known as relaxation oscillator.

47
13.2 Relaxation Oscillator
A nonlinear or relaxation oscillator produces a non-sinusoidal output, such as a square, saw
tooth or triangular wave. It consists of an energy-storing element (capacitor or, more rarely,
an inductor) and a nonlinear switching device (a latch, Schmitt trigger, or negative resistance
element) connected in a feedback loop. The switching device periodically charges and
discharges the energy stored in the storage element thus causing abrupt changes in the output
waveform.
Some of the more common relaxation oscillator circuits are listed below:
 Pearson-Anson oscillator
 Ring oscillator
 Delay line oscillator
 Royer oscillator
 Multivibrator
13.3 Royer Oscillator
A Royer oscillator is an electronic relaxation oscillator that employs a saturablecore
transformer. It was invented and patented in 1954 by George H. Royer. It has the advantages
of simplicity, low component count, rectangular waveforms, and easy transformer isolation.
By making maximum use of the transformer core, it also minimizes the size and weight of the
transformer. The classic Royer circuit outputs square; a modified version, essentially by
adding a capacitor, turns it into a harmonic oscillator, outputting sine waves. Both versions
are widely used, mainly as power inverters.

48
13.3.1 Circuit Description:
The circuit consists of a saturable-core transformer with a center-tapped primary winding, a
feedback winding and (optionally) a secondary winding. The two halves of the primary are
driven by two transistors in push-pull configuration. The feedback winding couples a small
amount of the transformer flux back in to the transistors bases to provide positive feedback,
generating oscillation. The oscillation frequency is determined by the maximum magnetic
flux density, the power supply voltage, and the inductance of the primary winding.
Figure 15: Circuit Description Of Royer Oscillator

49
13.4 Royer Oscillator in WPT
Magnetic coupling is attractive because it allows fairly large amounts of power to be
transmitted without need for high voltages. The basic idea is again to have two highQ
resonant circuits, which are now coupled magnetically and are preferred to have as low
characteristic impedance as possible.
The first modification to the circuit was to remove the fly back transformer and put an air
cored inductor in its place. To minimize the characteristic impedance of the tank circuit, we
first used a single loop of copper pipe. Tank capacitor was split into more parallel capacitors
of lower value for higher current rating, and also split the inductor in two going to drain of
each MOSFET, in order to avoid tapping the center of the copper loop.
13.4.1 Design :

50
Figure 16: Design Of Royer Oscillator
Our experimental realization of the scheme consists of two coils tuned at the same frequency.
An oscillation circuit is connected with a source coil S is in turn coupled resonant inductively
to a load carrying coil Q. The coils are made of an electrically conducting copper wire of a
cross-sectional radius wound into a concentric coil of multiple turn, radius r. Then a radio
frequency oscillating signal is passed through the coil S, it generates an oscillating magnetic
field through the inductance of the coil S, which is tuned at the same frequency by the
inductance of the coil and a resonating capacitor c. The load coil Q, tuned at the same
resonant frequency receives the power through the magnetic field generated by the source coil
S.
For the oscillator circuit presented, low ESR polypropylene capacitors are highly
recommended to handle the high current flowing through the LC tank. Moreover, other type
of capacitor creates high spikes in the sinusoidal wave at the LC tank circuit and affects the
MOSFETs. However, Mylar capacitors at first were used which has polyester as the dielectric.
The circuit became unstable by using this type of capacitor. Later MKP capacitors were used
which performed much better. At first, the transmitter circuit did not oscillate; instead one
MOSFET and inductor heated up rapidly. Later it was found that, short circuit was caused by
the voltage of power supply rising too slowly on power-up. This was solved by using a switch
on the low voltage side that is immediately between the oscillator circuit and the rectifier.
After the oscillator circuit started to oscillate very little power was available on the load coil.
Because the receiver coil was slightly out of resonance, it could not pick up the power
properly. This was solved by building both LC-tank circuits with identical loops and
capacitances,so that both the circuits have the same resonant frequency.
The following table shows the components which are used to make the oscillator :-
Table 3 : Components are used to make the oscillator
Components Name Components Value or code
Voltage Source, V dc 15V
Capacitor, C1 100nF

51
Capacitor, C 60nF
Resistor, R1 100Ω
Resistor, R2 100Ω
Resistor, R3 10kΩ
Resistor, R4 10kΩ
Diode, D1 1N4142
Diode, D2 1N4142
MOSFET, Q1 1RF1010
MOSFET, Q2 1RF1010
Radio Frequency Choke, L1 100

52
Radio Frequency Choke, L2 100
CHAPTER 14 ANTENNA DESIGN
14.1 Introduction
An antenna (plural antennae or antennas), or aerial, is an electrical device which converts
electric power into radio waves, and vice versa. It is usually used with a radio transmitter or
radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at
radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and
the antenna radiates the energy from the current as electromagnetic waves (radio waves). In
reception, an antenna intercepts some of the power of an electromagnetic wave in order to
produce a tiny voltage at its terminals, which is applied to a receiver to be amplified.Typically
an antenna consists of an arrangement of metallic conductors (elements), electrically
connected (often through a transmission line) to the receiver or transmitter. An oscillating
current of electrons forced through the antenna by a transmitter will create oscillating
magnetic fields around the antenna elements, while the charge of the electrons also creates an
oscillating electric field along the elements. These time-varying fields radiate away from the
antenna into space as a moving transverse electromagnetic field wave. Conversely, during
reception, the oscillating electric and magnetic fields of an incoming radio wave exert force
on the electrons in the antenna elements, causing them to move back and forth,creating
oscillating currents in the antenna.
14.2 Resonant Antenna
The majority of antenna designs are based on the resonance principle. This relies on the
behavior of moving electrons, which reflect off surfaces where the dielectric constant changes,
in a fashion similar to the way light reflects when optical properties change. In these designs,
the reflective surface is created by the end of a conductor, normally a thin metal wire or rod,
which in the simplest case has a feed point at one end where it is connected to a transmission
line. The conductor, or element, is aligned with the electrical field of the desired signal,
normally meaning it is perpendicular to the line from the antenna to the source (or receiver in
the case of a broadcast antenna).
14.2.1 Loop Antenna:

53
Loop antennas consist of a loop or coil of wire. Loops with circumference of a wavelength or
larger act similarly to dipole antennas. However loops small in comparison to a wavelength
act differently. They interact with the magnetic field of the radio wave instead of the electric
field as other antennas do, and so are relatively insensitive to nearby electrical noise.However
they have low radiation resistance, and so are inefficient for transmitting. They are used as
receiving antennas at low frequencies, and also as direction finding antennas.
14.3 DesignDetails
14.3.1 First Design :
Single turn coil, 18cm in diameter made of 6mm copper tube.
Resistance : 0. 1Ω
Inductance : 1µH
Q factor : 44.7
Resonant frequency : 520 kHz
Maximum distance : 3cm

54
Figure 17: Coil Design 1
14.3.2 Second Design :
75 turn coil, 16cm in diameter made of 0.51mm diameter aluminum wire.
Resistance : 5Ω

55
Inductance : 400µH
Q factor : 17.88

56
14.3.3 Third Design :
25 turn coil, 16cm in diameter made of 1.15 mm diameter copper wire.
Resistance : 0.3Ω
Inductance : 42µH
Q factor : 96.6

57
14.4 Comparison of the designs
Table 4 : Comparison of the designs

58
Design Description Resistance
Ω
Inductance
µH
Resonant
frequency
kHz
Distance
cm
Q
factor
1st Single turn coil,
18cm in diameter
made of 6mm
copper tube.
0.1 1 520 3 44.7
2nd 75 turn coil, 16cm
in diameter made
of 0.51mm
diameter
aluminum wire.
5 400 60 7 17.88
3rd 25 turn coil, 16cm
in diameter made
of 1.15 mm
diameter copper
wire.
0.3 42 114 40 96.6

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CHAPTER 15 FINAL ASSEMBLY
15.1 Introduction
Packaging is the technology of enclosing or protecting products for distribution, storage, sale,
and use. Packaging also refers to the process of designing, evaluating, and producingpackages.
Packaging can be described as a coordinated system of preparing goods for transport,
warehousing, logistics, sale, and end use. Packaging contains, protects, preserves, transports,
informs, and sells. In many countries it is fully integrated into government, business and
institutional, industrial, and personal use.
15.2 Purpose of packaging
Packaging and package labeling have severalobjectives
 Physical protection – The objects enclosed in the package may require protection from,
among other things, mechanical shock, vibration, electrostatic discharge, compression,
temperature,etc.

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 Barrier protection – A barrier to oxygen, water vapor, dust, etc., is often required.
Permeation is a critical factor in design. Some packages contain desiccants or oxygen
absorbers to help extend shelf life. Modified atmospheres or controlled atmospheres are
also maintained in some food packages. Keeping the contents clean, fresh, sterile and
safe for the duration of the intended shelf life is a primary function. A barrier is also
implemented in cases where segregation of two materials prior to end use is required, as
in the case of special paints, glues, medical fluids, etc. At the consumer end, the
packaging barrier is broken or measured amounts of material are removed for mixing and
subsequent end use.
 Convenience – Packages can have features that add convenience in distribution,
handling, stacking, display, sale, opening, reclosing, using, dispensing, reusing, recycling,
and ease of disposal.
15.3 Final Packaging
15.3.1 High Frequency Convertor:

61
Figure 20: High Frequency Converter 1

63
Figure 21: High Frequency Converter 2
15.4 HF Convertor Closed
Figure 22: HF Converter Closed 1

65
Figure 23: HF Converter Closed 2
15.5 Transmission and Receiving coils

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Figure 24: Transmission and Receiving coils
CHAPTER 16 RESULTS
16.1 CRO Waveforms
16.1.1 No load Input

68
Figure 25: CRO Waveforms At No Load Input
16.1.2 No load Output

69
Figure 26: CRO Waveforms At No Load Output

71
Figure 27: CRO Waveforms At No Loaded Output
CHAPTER 17 CONCLUSION
The goal of this project was to design and implement a wireless power transfer system via
magnetic resonant coupling. After analyzing the whole system systematically for optimization,
a system was designed and implemented. Experimental results showed that significant
improvements in terms of powertransfer efficiency have been achieved.
We have described and demonstrated that magnetic resonant coupling can be used to deliver
power wirelessly from a source coil to a load coil with an intermediate coil placed between
the source and load coil and with capacitors at the coil terminals providing a sample mean to
match resonant frequencies for the coils. This mechanism is a potentially robust means for
delivering wireless power to a receiver from a source coil.

73
CHAPTER 18 POSSIBLE APPLICATIONS AND FUTURE WORK
17.1 Applications:
1) Smart Phones,Portable Media Players, Digital Cameras and Tablets.
2) Public Access Charging Terminal.
1) Computer Systems
2) Miscellaneous: Wireless chargers are finding its way into anything with a battery inside it.
This includes game and TV remotes, cordless power tools, cordless vacuum cleaners, soap
dispensers, hearing aids and even cardiac pacemakers. Wireless chargers are also capable of
charging super capacitors (super caps), or any device that is traditionally powered by a
low-voltage power cable.
17.2 Future work:
To transmit the power to a greater distance, a high power radio frequency amplifier connected
with an oscillator is needed. But the construction of the bulky RF power amplifier requires
much time and patience.
High power vacuum tube transistor amplifier with high current will make the system more
efficient.
A crystal oscillator circuit might be a better option for the transmitter circuit since it can
produce a very high frequency A.C. current
.
Further effort on this same project can yield some real solutions that can solve the problems
of this project. The knowledge of this project will help those who want to design a wireless
charging system.

74
Figure 28: POSSIBLE APPLICATIONS AND FUTURE WORK

75
CHAPTER 18 REFERENCES
https://en.wikipedia.org/wiki/Wireless_power_transfer
https://markobakula.wordpress.com
http://4hv.org/e107_plugins/forum/forum_viewtopic.php?74096
http://www.instructables.com/id/ZVS-Driver/
http://electronics.stackexchange.com/questions/175170/understanding/
http://www.smps.us/inverters.html
http://wiki.4hv.org/index.php/Royer_oscillator
https://www.wirelesspowerconsortium.com/
http://www.icnirp.org/en/frequencies/high-frequency/index.html
http://www.eurekalert.org/pub_releases/2014-04/tkai-wpt041714.php

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CHAPTER 19 BIOGRAPHY
1) Jacob Millman and Christos C. Halkias, ―Integrated Electronics: Analog and Digital
Circuits and Systems
2) Muhammad H. Rashid, ―Power Electronics: Circuits, Devices,and Applications
3) Robert L. Boylestad and Louis Nashelsky, Electronic Devices and Circuit Theory
4) William H.Hayt,Jr. and John A.Buck, Engineering Electromagnetics

78
APPENDIX
1) Datasheet of MOSFET IRF540.
2) Datasheet of OA79.
3) Datasheet of LM7812.

Wireless Power Transmission Project Report

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