1.INTRODUCTION

In our present electricity generation system we waste more than half of its resources.

Especially the transmission and distribution losses are the main concern of the present power

technology. Much of this power is wasted during transmission from power plant generators to

the consumer. The resistance of the wire used in the electrical grid distribution system causes

a loss of 26-30% of the energy generated. This loss implies that our present system of

electrical distribution is only 70-74% efficient.

And We know that large amount of solar power is available in the outer space the power can

be used to limit some of the power problems. The power available cannot transmit through

wires at outer space so micro wave technology is used transmission which is wireless. The

transmission of power without wires may be one noble alternative for electricity

transmission.

This concept of wireless power technology was proposed by Nicholas tesla in 1893 and he

started a wardenclyff tower project to transmit power wirelessly which has been stopped due

to economical problems. His proposal is that power can be transmitted without using wires

using electromagnetic waves or by electrifying the ionosphere.

So in this project we mainly concentrate on tesla`s principle of transmitting the power

through electromagnetic waves and in this project our main aim is to develop a prototype

wireless system using strongly coupled electromagnetic waves which can transfer power over

1-2feet distance.

The definition of Wireless Power Transmission (WPT) is: efficient transmission of electric

power from one point to another trough vacuum or an atmosphere without the use of wire

or any other substance. This can be used for applications where either an instantaneous

amount or a continuous delivery of energy is needed, but where conventional wires are

unaffordable, inconvenient, expensive, hazardous, unwanted or impossible. The power can

be transmitted using microwaves, millimeter wave or lasers. WPT is a technology that can

transport power to locations, which are otherwise not possible or impractical to reach.

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2.BACKGROUND

Although  it was not until 1954-1959 when  experimental  measurements 

were  made of the frequency that is propagated in the  resonant  cavity    surrounding  the

Earth, recent analysis shows that it was Nikola  Tesla    who,  in 1899, first noticed the

existence of stationary waves  in  the  Schumann cavity.  Tesla's experimental

measurements of the wave length and   frequency   involved   closely   match  

Schumann's   theoretical   calculations.  Some of these observations were made in 1899

while Tesla was   monitoring  the  electromagnetic  radiations  due  to   lightning 

discharges  in  a hunderstorm which passed over his  Colorado  Springs laboratory  and 

then  moved more than 200 miles  eastward  across  the  plains.   In his  Colorado  Springs 

Notes,  Tesla  noted  that  these  stationary waves "... can be produced with an oscillator,"

and added in parenthesis,  "This is of immense importance."6 The importance of  his 

observations is due to the support they lend to the prime objective of the Colorado Springs

laboratory.  The intent of the experiments and the laboratory Tesla   had constructed was 

to prove  that  wireless transmission of electrical power was possible

  Schumann Resonance is analogous to pushing a pendulum.  The intent of    Project Tesla

is to create pulses or electrical disturbances that would    travel in all directions around the

Earth in the thin membrane of  non-conductive  air between the ground and the ionosphere. 

The  pulses  or waves would follow the surface of the Earth in all directions expanding

outward  to  the  maximum circumference of the  Earth  and  contracting inward  until

meeting at a point opposite to that of  the  transmitter. This  point  is  called the anti-pod. 

The traveling waves  would  be reflected  back from the anti-pode to the transmitter to

be  reinforced and sent out again.

      At  the  time of his measurements Tesla was  experimenting  with  and   researching 

methods  for "power transmission  and  transmission  of  intelligible  messages to any point

on the globe."  Although Tesla  was  not  able to commercially market a system to transmit

power around  the globe,  modern scientific theory and mathematical calculations  support

his  contention  that the wireless propagation of electrical  power  is possible and a feasible

alternative to the extensive and costly grid of electrical   transmission  lines  used  today 

for   electrical power  distribution. Tesla did experiments in the field of pulsed wireless 2

energy transfer in 1899. Tesla's Magnifying Transmitter, an early type of Tesla Coil that

measured 16 meters in diameter, could transmit tens of thousands of watts without wires.

Tesla supposedly managed to light 200 lamps, without wires, from 40kilometers away. No

documentation from Tesla's own records has been published validating that this actually

happened. In 1897, he filed his first patents dealing with Wardenclyff tower. This aerial

tower was meant to be a pilot plant for his “World Wireless System” to broadcast energy

around the globe. The core facility was never fully operational and was not completed due

to economic problems.

The Raytheon Company did the first successful WPT experiment in 1963.In this

experiment energy was transmitted with a DC-to-DC efficiency of 13%. This company also

demonstrated a microwave-powered helicopter in 1964. The Jet propulsion lab of NASA

carried out an experiment and demonstrated the transfer of 30 kW over a distance of 1 mile

in 1975. They used an antenna array erected at the Goldstone facility. This test

demonstrated the possibilities of wireless power outside the laboratory.

Rockwell International and David Sarnoff Laboratory operated in 1991 a microwave

powered rover at 5.86 GHz. Three kilowatts of power was transmitted and 500 watts was

received.

This paper provides an overview of the technologies, possibilities and uses of wireless

power transmission. An overall view of the past present and possible transmission systems

are presented. In this paper also the different systems; economical, ecological and social

aspects are discussed. The paper focuses on wireless power transmission systems with

microwaves in the power range of about 100 W to 100 kW.

The Nicholas tesla had designed a tower called Wardenclyff tower or tesla tower through

which he thought of availing world for wireless power systems and this tower was stopped

due to economical problems.

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Fig 2.0 Wardenclyff tower

2.1 State of the art of WPT technology:

In order to transport electricity is has to be transformed into a suitable energy form. For

wireless transmission, this has to be a form that can travel trough air. Microwave frequencies

hold this ability. The microwave spectrum is defined as electromagnetic energy ranging from

approximately 1 GHz to 1000 GHz in frequency, but older usage includes lower frequencies.

Most common applications are within the 1 to 40 GHz range.

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A complete microwave transmission system consists of three essential parts:

Electrical power to microwave power conversion

Absorption antenna that captures the waves

Re conversion to electrical power

The components include a microwave source, a transmitting antenna and a receiving antenna.

The microwave source consists of an electron tubes or solid-state devices with electronics to

control power output. The slotted waveguide antenna, parabolic dish and micro strip patch are

the most popular types. Due to high efficiency (>95%) and high power handling capacity, the

slotted waveguide antenna seems to be the best option for power transmission. The

combination of receiving and converting unit is called rectenna. The rectenna is a rectifying

antenna that is used to directly convert microwave energy into DC electricity. It is an antenna

includes a mesh of dipoles and diodes for absorbing microwave energy from a transmitter and

converting it into electric power. Its elements are usually arranged in a multi element phased

array with a mesh pattern reflector element to make it directional.

One of the disadvantages is that microwaves have long wavelengths that exhibit a moderate

amount of diffraction over long distances. The Rayleigh criterion dictates that any beam will

spread (microwave or laser), become weaker, and diffuse over distance. The larger the

transmitter antenna or laser aperture, the tighter the beam and the less it will spread as a

function of distance (and viceversa). Therefore, the system requires large transmitters and

receivers. The used power density of the microwave beam is normally in de order of 100

W/m2. This is relative low compared to the power density of solar radiation on earth (1000

W/m2) and chosen this way for safety reasons.

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2.2 Methods of wireless power transmission:

Micro wave technology

Radio wave technology

Magnetic induction

Resonance

2.2.1 Micro wave technology:

Microwave power transmission (MPT) is the use of microwaves to transmit power through

outer or the atmosphere without the need for wires. It is a sub-type of the more general

wireless methods. MPT is the most commonly proposed method for transferring energy to the

surface of the Earth from solar power satellites or other in-orbit power sources. The output

microwave power ranges from 50 W to 200 W at 2.45GHz.MPT is occasionally proposed for

the power supply in beam-powered propulsion for orbital lift space ships. Although lasers are

more commonly proposed, their low efficiency in light generation and reception has led some

designers to opt for microwave based systems.

Wireless 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 .

It is known that electromagnetic energy also associated with the propagation of the

electromagnetic  waves.  We  can  use  theoretically  all  electromagnetic  waves  for  a  wirele

ss  power transmission (WPT). The difference between the WPT and communication  systems 

is only efficiency.

The   Maxwell’s   Equations   indicate   that   the   electromagnetic   field   and   its   power   di

ffuse   to all directions. Although we transmit the energy in the communication system, 

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the transmitted energy is diffused to all directions. Although the received power is enough 

for a  transmission of information,the  efficiency  from  the  transmitter  to   receiver  is

quiet  low.  Therefore, we do not call  it  the  WPT system.ypical  WPT  is  a  point-to-point   

power  transmission.  For the WPT,  we  had  better  concentrate power to  receiver.  It was

proved that the power transmission efficiency can approach close to 100%.We can 

more concentrate the transmitted microwave power to the receiver aperture areas with taper

method of  the  transmitting  antenna  power  distribution.  Famous power  tapers  of  

the  transmitting antenna  are  Gaussian  taper,  Taylor  distribution,  and   Chebychev  

distribution.  These  taper  of  the transmitting  antenna  is commonly  used  for   suppression  

of  sidelobes.  It corresponds  to  increase the power transmission efficiency.  Concerning 

the power transmission efficiency of the WPT, there are some good optical  approaches 

in Russia.

Future  suitable  and  largest  application  of  the  WPT  via  microwave  i

s  a  Space  Solar   Power

Satellite  (SPS).  The  SPS  is  a  gigantic  satellite  designed  as  an  electric   power  

plant  orbiting  in  the Geostationary  Earth  Orbit  (GEO).  It  consists  of  mainly   three   

segments;  solar  energy collector  to convert the  solar  energy  into   DC  (direct current) 

electricity,  DC-to-microwave  converter,  and large antenna array  to beam down the

microwave power to the ground.The first solar collector can be either photovoltaic  cells or 

solar thermal turbine. The second DC-to-microwave  converter of the SPS can be either 

microwave  tube system and/or semiconductor system.  It may be their combination.  The

third   segment   is   a   gigantic   antenna   array.  Table   1.1   shows   some   typical    

parameters of   thetransmitting antenna of the SPS. An amplitude taper on the 

transmitting antenna is adopted in orderto increase the beam collection efficiency  and to

decrease  side lobe level in almost all SPS design. A typical  amplitude  taper   is  called   

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10  dB   Gaussian in  which   the  power  density  in  the  center  of  the transmitting antenna

is ten times larger than  that on the edge of the transmitting antenna.

The SPS is expected to realize around 2030. Before the realization of the SPS, we can 

Consider theother   application   of   the   WPT.   In   resent   years,   mobile   devices 

Advance quickly   and   required decreasing power consumption. It means that we can use 

the diffused weak microwave power as a power   source  of  the mobile  devicesc

with  low  power  consumption  such  as  RF-ID.  The RF-ID is a

Model Old JAXAmodel

JAXA1 model JAXA2 Model NASA/DOEmodel

Frequency 5.8 GHz 5.8 GHz 5.8 GHz 2.45 GHzDiameter oftransmitting antenna

2.6 km 1 km 1.93 km 1 km

Amplitude taper 10 dB Gaussian 10 dB Gaussian 10 dB Gaussian 10 dB GaussianOutput power(beamed to earth)

1.3 GW 1.3 GW 1.3 GW 6.72 GW

Maximum powerdensity at center

263 mW/ cm

2420 mW/cm

2114 mW/cm

22.2 W/ cm

Minimum powerdensity at edge

26.3 mW/ cm

242 mW/ cm

211.4 mW/cm

20.22 W/ cm

Antenna spacing 0.75 λ 0.75 λ 0.75 λ 0.75 λPower per one antenna(Number of elements)

Max. 0.95 W(3.54 billion)

Max. 6.1W(540 million)

Max. 1.7 W(1,950 million)

Max. 185 W(97 million)

Rectenna Diameter 2.0 km 3.4 km 2.45 km 1 kmMaximum Power

Density2

180 mW/cm2

26 mW/cm 100 mW/cm2 223 mW/cm

Collection Efficiency 96.5 % 86 % 87 % 89 %

Table 2.2.1

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radio IC- tug with wireless power transmission and wireless information. This is a

new WPT application like broadcasting.

2.2.2. Radio wave technology:

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic

spectrum longer than infrared light. Naturally-occurring radio waves are produced

by lightning, or by astronomical objects. Artificially-generated radio waves are used for fixed

and mobile radio, broadcasting, radar and other navigation systems, satellite communication,

computer networks and innumerable other applications. Different frequencies of radio waves

have different propagation characteristics in the Earth's atmosphere; long waves may cover a

part of the Earth very consistently, shorter waves can reflect off the ionosphere and travel

around the world, and much shorter wavelengths bend or reflect very little and travel on a line

of sight.

Radio wave technology can transmit the power over kilometers but the amount of power

transmission is low. The frequency is in order of GHz.

Electrical currents that oscillate at RF have special properties not shared by direct

current signals. One such property is the ease with which they can ionize air to create a

conductive path through air. This property is exploited by 'high frequency' units used in

electric arc welding, although strictly speaking these machines do not typically employ

frequencies within the HF band. Another special property is an electromagnetic force that

drives the RF current to the surface of conductors, known as the skin effect. Another property

is the ability to appear to flow through paths that contain insulating material, like

the dielectric insulator of a capacitor. The degree of effect of these properties depends on the

frequency of the signals.

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Electrical currents that oscillate at RF have special properties not shared by direct

current signals. One such property is the ease with which they can ionize air to create a

conductive path through air. This property is exploited by 'high frequency' units used in

electric arc welding, although strictly speaking these machines do not typically employ

frequencies within the HF band. Another special property is that RF current cannot penetrate

deeply into electrical conductors but flows along the surface of conductors; this is known as

the skin effect. Another property is the ability to appear to flow through paths that contain

insulating material, like the dielectric insulator of a capacitor. The degree of effect of these

properties depends on the frequency of the signals.

2.2.3 Magnetic induction:

Electromagnetic induction is the production of voltage across a conductor situated in a

changing magnetic field or a conductor moving through a stationary magnetic field.

Faraday found that the electromotive force (EMF) produced around a closed path is

proportional to the rate of change of the magnetic flux through any surface bounded by that

path.

In practice, this means that an electrical current will be induced in any closed circuit when the

magnetic flux through a surface bounded by the conductor changes. This applies whether the

field itself changes in strength or the conductor is moved through it.

Electromagnetic induction underlies the operation of generators, all electric

motors, transformers, induction motors, motors, solenoids, and most other electrical machines.

The "electrodynamics inductive effect" or "resonant inductive coupling" has key implications

in solving the main problem associated with non-resonant inductive coupling for wireless

energy transfer; specifically, the dependence of efficiency on transmission

distance. Electromagnetic induction works on the principle of a primary coil generating a

predominantly magnetic field and a secondary coil being within that field so a current is

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induced in the secondary. This results in a negligible range because most of the magnetic field

misses the secondary. Over relatively small distances the induction method is inefficient and

wastes much of the transmitted energy.

The application of resonance improves the situation somewhat, moderately improving the

efficiency by "tunneling" the magnetic field to a receiver coil that resonates at the same

frequency. When resonant coupling is used the two inductors are tuned to a mutual frequency

and the input current is modified from a sinusoidal into a non sinusoidal rectangular or

transient waveform. So as to more aggressively drive the system. In this way significant power

may be transmitted over a range of many meters. Unlike the multiple-layer windings typical of

non-resonant transformers, such transmitting and receiving coils are usually single

layer solenoids or flat spirals with series capacitors, which, in combination, allow the

receiving element to be tuned to the transmitter frequency and reduce losses.

Fig 2.2.3 Project on WPT by MIT, USA

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The electrodynamic induction wireless transmission technique is near field over distances up

to about one-sixth of the wavelength used. Near field energy itself is non-radiative but some

radiative losses do occur. In addition there are usually resistive losses. With electrodynamic

induction, electric current flowing through a primary coil creates a magnetic field that acts on

a secondary coil producing a current within it. Coupling must be tight in order to achieve high

efficiency. As the distance from the primary is increased, more and more of the magnetic field

misses the secondary. Even over a relatively short range the inductive coupling is grossly

inefficient, wasting much of the transmitted energy.

This action of an electrical transformer is the simplest form of wireless power transmission.

The primary and secondary circuits of a transformer are not directly connected. Energy

transfer takes place through a process known as mutual induction. Principal functions are

stepping the primary voltage either up or down and electrical isolation. Mobile phone and

electric toothbrush battery chargers, and electrical power distribution transformers are

examples of how this principle is used. Induction cookers use this method. The main

drawback to this basic form of wireless transmission is short range. The receiver must be

directly adjacent to the transmitter or induction unit in order to efficiently couple with it.

The application of resonance increases the transmission range somewhat. When resonant

coupling is used, the transmitter and receiver inductors are tuned to the same natural

frequency. Performance can be further improved by modifying the drive current from a

sinusoidal to a nonsinusoidal transient waveform. Pulse power transfer occurs over multiple

cycles. In this way significant power may be transmitted between two mutually-attuned LC

circuits having a relatively low coefficient of coupling. Transmitting and receiving coils are

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usually single layer solenoids or flat spirals with series capacitors, which, in combination,

allow the receiving element to be tuned to the transmitter frequency.

Common uses of resonance-enhanced electrodynamic induction are charging the batteries of

portable devices such as laptop computers and cell phones, medical implants and electric

vehicles. A localized charging technique selects the appropriate transmitting coil in a

multilayer winding array structure. Resonance is used in both the wireless charging pad (the

transmitter circuit) and the receiver module (embedded in the load) to maximize energy

transfer efficiency. This approach is suitable for universal wireless charging pads for portable

electronics such as mobile phones. It has been adopted as part of the Qi wireless charging

standard.

It is also used for powering devices having no batteries, such as RFID patches and contactless

smartcards, and to couple electrical energy from the primary inductor to the helical resonator

of Tesla coil wireless power transmitters.

2.2.4 Resonance:

Electrical   resonance occurs in an electric circuit at a particular resonance frequency when

the impedance between the input and output of the circuit is at a minimum (or when

the transfer function is at a maximum). Often this happens when the impedance between the

input and output of the circuit is almost zero and when the transfer function is close to one.

Resonant circuits exhibit ringing and can generate higher voltages and currents than are fed

into them. They are widely used in wireless transmission for both transmission and reception.

Resonance occurs in electrical circuits as well, where it is used to select or "tune" to specific

frequencies.  Resonant   energy   transfer or resonant   inductive   coupling is the short-

distance wireless transmission of energy between two coils that are highly resonant at the

same frequency. The equipment to do this is sometimes called a resonant transformer. While

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many transformers employ resonance, this type has a high Q and is nearly always air-cored to

avoid 'iron' losses. The coils may be present in a single piece of equipment or in separate

pieces of equipment.

With the developments of mobile and implantable devices, wireless power transfer (WPT) has

become increasingly necessary to free a variety of electronic systems from using power cords

and batteries. WPT is especially important in providing medical implants with an alternative

power source since changing battery in an implant implies a surgery. In recent years, several

WPT methods have emerged, including magnetic induction and omnidirec- tional or

unidirectional electromagnetic radiation. In 2007, a magnetic resonant coupling WPT method

was reported which brought the research on WPT to a new climax. This new method transmits

power wirelessly in the mid-range, which represents several times the average radius of the

resonators in the WPT system. The energy transmission efficiency of the new method is much

higher than the magnetic induction method. In addition, the new method does not suffer from

the tracking problem as the unidirectional electromagnetic radiation method does. Despite the

advantages, a simple two-resonator WPT system has limited applications due to the

insufficient transmission range in many practical applications. A multiple-resonator system

provides an effective solution to this problem, but has not yet been fully understood despite

the recent interest in this subject. In this thesis, the three- resonator relayed WPT system is

analyzed theoretically. The coupled mode theory (CMT) is utilized to find the optimal relay

position at which the maximum efficiency is achieved. Experiments were performed which

verified the results of our theoretical analysis. It was found that the relay resonator increased

the WPT distance significantly while providing ahigh energy transfer efficiency.

As an important application, we constructed a new platform for performing biological

experiments on laboratory rodents implanted with miniature devices. Our WPT system

supplies a sufficient amount energy to the implanted devices regardless of the locations of

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rodents in the platform. A new hexagonal PCB based resonator was designed. Seven such

resonators were fabricated and placed under the platform in a unique pattern. These resonators

transmit power to an innovative receiving resonator which is integrated within the container of

an implanted device.

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 to it,

the coil can pick up most of the energy before it is lost, even if it is some distance away.

Resonant energy transfer is the operating principle behind proposed short range wireless

electricity systems such as WiTricity and similar systems.

 Resonant transformers such as the Tesla coil can generate very high voltages without arcing,

and are able to provide much higher current than electrostatic high-voltage generation

machines such as the Van de Graff generator. 

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Resonant Induction recharging:-

Fig. 2.2.4 Resonant Induction recharging

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3.0 Principle used in WPT:

The main principle used in this type of wireless power transmission using inductive coupling.

The idea behind the project was to create a small tabletop demonstrator of magnetically

coupled wireless power transfer, resembling a miniature version of the MIT 'witricity' device.

The goal was to keep the circuit simple with easily obtainable parts, and to keep voltage and

power levels low so the device is safe for handling and doesn't require special methods of

cooling.

The basic idea is to feed a parallel LC tank circuit from an AC voltage source at it's resonant

frequency, which allows large reactive current to circulate in the circuit while only real power

is being drawn from the source. This sets up a large alternating magnetic field in the inductor,

which is designed as a single conductive loop in this case.

Now, another LC tank with load attached is brought in proximity to the excited LC circuit,

significant amounts of power can be transferred via weak magnetic coupling between them.

This is because AC current itself in the transmitting loop is very large, and inductive reactance

of the receiver loop is canceled out by the capacitor.

For a practical device, the AC voltage source had to be substituted with an appropriate

oscillator, which would take feedback from the tank circuit itself and hence always drive it at

it's resonant frequency.

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3.1 Block Diagram of Wireless power Transmission:-

Fig 3.1 Block Diagram of Wireless power Transmission

3.2 List of Components Used:-

3.2.1 Components used in Power Supply Unit:

S. No. Component Description Rating Quantity

1 Transformer (StepDown Transformer) 230/15V, 6A 1

2 Bridge KBR 1010 (10A) 1

3 Voltage Regulator 7812(TO3 Package, 5A) 1

4 Capacitor C1 2200uf, 50V 1

5 Capacitor C2 1000uf, 25V 1

6 Capacitor C3 1uf (Box Type) 1

Table 3.2.1 Components used in power supply unit

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3.2.2 Components used in Transmitter Unit:

S. No. Component Description Rating Quantity

1 LED Green 1

2 Resistors 1K Ohm 1

3 Resistors 10K Ohm 2

4 Resistors 100 Ohm 2

5 Diodes 1N4148 2

6 Capacitor 100n/63 V 1

7 Inductors100uH(10A) 2

8Mosfet with Heat Sink IRFZ44N 2

9Capacitors (Polypropylene) 6.8nF (1000V or more) 10

10Copper Tube 6mm 1

Table 3.2.2 Components used in Transmitter unit

3.2.3 Components used in Receiver Unit:

S. No. Component Description Rating Quantity

1 Capacitors (Polypropylene) 48.3nF (630V or more) 1

2 Bulb 12V, 5W 1

3 Copper wire 3mm Solid 1

Table 3.2.3 Components used in Receiver Unit

3.3 Power supply unit:

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The power supply unit consists of 230/15v 6Amp ac step down transformer. The specially

designed transformer can maintain the constant voltage of 15v up to 6Amperes of load. The

15v ac is given to rectifier unit which converts ac to dc.

Fig 3.3 Circuit Diagram of Power Supply Unit

D1, D2 = Diodes 1N4003D3 = Diode 1N4001 C1 = 1000 Micro Farad aluminum electrolytic capacitor

C2 = 10 Micro Farad aluminum electrolytic capacitor

IC1=7812 for +12V DC output

The power supply consists of transformer which converts the 230 to 15v ac and thereby the 15

v ac is converted into dc by using rectifier unit. The rectifier unit consists of regulators and

diodes.

3.4 Rectifier unit:

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The rectifier unit takes the input as 15v AC from power supply transformer and it converts the

15V AC to DC. The regulators used in this power supply are 7812 TO3 package. And the

bridge used in this circuit is KBR1010 which can withstand 10 amperes of current.

Fig 3.4 Circuit Diagram of Rectifier Unit

The capacitor used in the circuit is to smooth out the dc voltage obtained.

3.5 Transmitter unit:

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The transmitter unit generates the high frequency using the oscillator and the power will be

transmitted through the electromagnetic waves and with air as the medium The transmitter

takes the 15v dc as the input and the power will be transmitted to the receiver unit by using the

strongly coupled electromagnetic waves. The power transmitted is around 6watts.the

transmitter unit will consists of mosfet irfz44n used to produce the oscillations and the

transmitter unit consists of tank circuit which is used to tune the transmitter and the receiver

unit.

Fig 3.5 Transmitter unit

The transmitter unit main components are:

Oscillating circuit

Tank circuit

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Inductors

3.5.1 Oscillating circuit:

To produce the high frequency the oscillator circuit is constructed. The produced oscillations

are in order of 1.5Mhz.The oscillator works on the principle of the mazzilli fly back oscillator.

The two Mosfets are connected back to back in this circuit which conducts alternately to

produce the oscillations.

Fig 3.5.1 Oscillating circuit in the transmitter

The oscillating circuit consists of oscillating Mosfets which are responsible for producing the

frequency. A self-excited solid-state oscillator for supplying a high-power RF inductive load.

The oscillator includes at least one MOSFET transistor connected in a self-excited oscillator

configuration, an output tuned circuit including an inductive load and a tank circuit connected

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to the load, the tank circuit having a resonant frequency determined at least in part by the

inductance of the load, an RF feedback transformer coupling the tank circuit to the gate of the

MOSFET for providing a switching signal to the MOSFET for causing the MOSFET to

alternate between the on state and the off state at a frequency equal to the resonant frequency

of the tank circuit, and a bias circuit for superimposing a forward bias voltage on the switching

signal. So, the Mosfets used in this circuit are IRFZ44N.

3.5.1.1 Mosfets(IRFZ44N):

The Mosfets are used for producing the oscillations and thereby high frequency is generated

which is used to generate the electromagnetic waves.

A Power MOSFET is a specific type of metal oxide semiconductor field-effect transistor

(MOSFET) designed to handle large amounts of power. Compared to the other power

semiconductor devices (IGBT, Thyristor...), its main advantages are high commutation speed

and good efficiency at low voltages. It shares with the IGBT an isolated gate that makes it

easy to drive.

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Fig 3.5.1.1 N-Channel Power MOSFET

A traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer

of silicon dioxide (Si O 2) on top of a silicon substrate and depositing a layer of metal

or polycrystalline silicon(the latter is commonly used). As the silicon dioxide is

a dielectric material, its structure is equivalent to a planar capacitor, with one of the electrodes

replaced by a semiconductor.

When a voltage is applied across a MOS structure, it modifies the distribution of charges in

the semiconductor. If we consider a P-type semiconductor (with NA the density of

acceptors, p the density of holes; p = NA in neutral bulk), a positive voltage, VGB, from gate

to body (see figure) creates a depletion layer by forcing the positively charged holes away

from the gate-insulator/semiconductor interface, leaving exposed a carrier-free region of

immobile, negatively charged acceptor ions (see doping (semiconductor)). If VGB is high

enough, a high concentration of negative charge carriers forms in an inversion layer located in

a thin layer next to the interface between the semiconductor and the insulator. Unlike the

MOSFET, where the inversion layer electrons are supplied rapidly from the source/drain

electrodes, in the MOS capacitor they are produced much more slowly by thermal generation

through carrier generation and recombination centers in the depletion region. Conventionally,

the gate voltage at which the volume density of electrons in the inversion layer is the same as

the volume density of holes in the body is called the threshold voltage.

This structure with P-type body is the basis of the N-type MOSFET, which requires the

addition of an N-type source and drain regions. A metal–oxide–semiconductor field-effect

transistor (MOSFET) is based on the modulation of charge concentration by a MOS

capacitance between a body electrode and a gate electrode located above the body and

insulated from all other device regions by a gate dielectric layer which in the case of a

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MOSFET is an oxide, such as silicon dioxide. If dielectrics other than an oxide such as silicon

dioxide (often referred to as oxide) are employed the device may be referred to as a metal–

insulator–semiconductor FET (MISFET). Compared to the MOS capacitor, the MOSFET

includes two additional terminals (source and drain), each connected to individual highly

doped regions that are separated by the body region. These regions can be either p or n type,

but they must both be of the same type, and of opposite type to the body region. The source

and drain (unlike the body) are highly doped as signified by a '+' sign after the type of doping.

If the MOSFET is an n-channel or nMOS FET, then the source and drain are 'n+' regions and

the body is a 'p' region. As described above, with sufficient gate voltage, above a threshold

voltage value, electrons from the source (and possiblyalso the drain) enter the inversion layer

or n-channel at the interface between the p region and the oxide. This conducting channel

extends between the source and the drain, and current is conducted through it when a voltage

is applied between source and drain.

For gate voltages below the threshold value, the channel is lightly populated, and only a very

small sub threshold leakage current can flow between the source and the drain.

If the MOSFET is a p-channel or pMOS FET, then the source and drain are 'p+' regions and

the body is a 'n' region. When a negative gate-source voltage (positive source-gate) is applied,

it creates a p-channel at the surface of the n region, analogous to the n-channel case, but with

opposite polarities of charges and voltages. When a voltage less negative than the threshold

value (a negative voltage for p-channel) is applied between gate and source, the channel

disappears and only a very small sub threshold current can flow between the source and the

drain.

The source is so named because it is the source of the charge carriers (electrons for n-channel,

holes for p-channel) that flow through the channel; similarly, the drain is where the charge

carriers leave the channel.

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The device may comprise a Silicon On Insulator (SOI) device in which a Buried OXide

(BOX) is formed below a thin semiconductor layer. If the channel region between the gate

dielectric and a Buried Oxide (BOX) region is very thin, the very thin channel region is

referred to as an Ultra Thin Channel (UTC) region with the source and drain regions formed

on either side thereof in and/or above the thin semiconductor layer. Alternatively, the device

may comprise a Semiconductor On Insulator (SEMOI) device in which semiconductors other

than silicon are employed. Many alternative semiconductor materials may be employed.

When the source and drain regions are formed above the channel in whole or in part, they are

referred to as Raised Source/Drain (RSD) regions.

Fig 3.5.1.2 Representation of pins of mosfet

3.5.2 Tank circuit(L-C):

The tank circuit of the transmitter consists of bank of capacitors and the loop of the inductor

(copper loop).The tank circuit is used for resonance. In this tank circuit the copper loop acts as

an inductor. The circuit consists of bank of capacitors which are connected in parallel.

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Fig 3.5.2 Bank of capacitors

The capacitors used in the transmitting circuit is of 6.8nf,1600v polypropylene type. It's

important that capacitors are polypropylene dielectric and foil or foil film based - other types

will heat up and melt in this application. Number of capacitors was later increased to 8,

removing the need of additional tuning. This prototype, though, had one problem - if the

supply voltage rose too slowly, such as while DC filter capacitance is charging, it tended to

fail to oscillate and just keep shorting the power supply with one mosfet ON. In the final

design this was solved with a relay, which acts as under voltage lockout of sorts, applying Ugg

power rapidly after supply voltage rose high enough.

A copper tube is used as a inductor. The tube is made up of copper and the tube is 6mm

thickness hallow tube which is connected to the capacitors to produce the resonance.

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The LC tank circuit is the part where heavy current circulates, and is required to be sturdy.

The copper pipe used as conductor heats up significantly under ~20A it's passing continuously

to handle the current while keeping losses tolerable, capacitor consists of 6 paralleled 6.8nF

1000V are used.

Fig 3.5.2.1 Copper loop with ferrite core

3.5.3 Radio frequency chokes:

A choke is an inductor designed to block (have a high reactance to) a particular frequency in

an electrical while passing signals of much lower frequency or direct current.

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Chokes used in radio circuits are divided into two classes – those designed to be used with

power and audio frequencies, and the others to be used with radio frequencies.

Audio frequency coils, usually called A.F. chokes, usually have ferromagnetic iron cores to

increase their inductance. Chokes were used as filters, in conjunction with large electrolytic

capacitors, in power supplies; working at low power-line frequencies they were large, heavy,

and expensive, but more effective and power-efficient than resistor-capacitor hum filters.

Modern components and circuits, with very large and cheap electrolytic capacitors and

electronic circuits which suppress hum, have long made chokes obsolete in mains-frequency

power supplies, although small and inexpensive inductors are used in high-frequency switch-

mode power supplies.

Chokes for higher frequencies often have iron powder or ferrite cores (see Ferrite bead). They

are often wound in complex patterns (basket winding) rather than regularly to reduce self-

capacitance. Chokes for even higher frequencies have non-magnetic cores and low inductance.

3.5.3 .1 Common-mode choke

Common-mode choke coils[clarification needed] are useful in a wide range of prevention of

electromagnetic interference (EMI) and radio frequency interference (RFI) from power supply

lines and for prevention of malfunctioning of electronic equipment. They pass differential

currents (equal but opposite), while blocking common-mode currents.[1]

3.5.3 .2 Solid-state chokes

Solid-state chokes (SSC)[clarification needed] can manage higher currents than simple passive

Inductors.

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Choke coils are inductances that isolate AC frequency currents from certain areas of a radio

circuit. Chokes depend upon the property of self-inductance for their operation. They can be

used to block alternating while passing direct current (contrast with capacitor). Common-

mode choke coils are useful in a wide range of prevention of electromagnetic

interference (EMI) and radio frequency interference (RFI) from power supply lines and for

prevention of malfunctioning of electronic equipment.

Solid-state chokes (SSC) can manage higher currents than traditional chokes. They can help

reduce the high frequency buzzing noises that occur when running under high electrical

currents.

The radio frequency chokes used in this circuit are were 100uH,10amperes at first iron powder

cores, but later switched to ferrite which produced much better results. Powdered iron cores

tended to heat up from magnetic flux they picked up from the transmitting loop.

Fig 3.5.3 Radio frequency choke

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3.5.4 Ferrite cores:

Ferrite cores are used at transmitter and receiver unit to tune the circuit for better power

transfer. Generally the ferrite cores are used for high frequency applications.

The ferrite core in this circuit is used for tuning the tank circuit.

Ferrite is a class of ceramic material with useful electromagnetic properties and an interesting

history. Ferrite is rigid and brittle. Like other ceramics, ferrite can chip and break if handled

roughly. Luckily it is not as fragile as porcelain and often such chips and cracks will be merely

cosmetic. Ferrite varies from silver gray to black in color. The electromagnetic properties of

ferrite materials can be affected by operating conditions such as temperature, pressure, field

strength, frequency and time.

Fig 3.5.4 Ferrite core

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There are basically two varieties of ferrite: soft and hard. This is not a tactile quality but rather

a magnetic characteristic. 'Soft ferrite' does not retain significant magnetization whereas 'hard

ferrite' magnetization is considered permanent.

3.6 Receiver unit:

The power transmitted by the transmitter unit will be received by the receiver unit wirelessly.

the power transfer takes place by using the inductive coupling. The receiver unit consists of a

tank circuit which is in resonance with the transmitter unit.

The power received by the receiver is in the order of 6 watts. The receiver circuit capacitance

will provided by a single capacitor which is the total of the capacitance at the transmitter unit.

a single total capacitance is provided instead of eight parallel capacitors because of the

circulating current in individual capacitors. The capacitor used at the receiving unit is also a

polypropylene type with 54.9nf,1600volts capacity.

On the receiver side only a single capacitor and a loop of 3mm solid copper wire was used.

The wire heats up significantly, a small matching inductor in series with the load, which is a

24V 5W. It's choice was guessed at 6uH and it improved performance somewhat at larger

distances.

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Fig 3.6 Receiving unit

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3.7 Circuit Diagram og Wireless power Transmission kit

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3.8 Wireless Power Transmission Kit

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4.0 Operation:

The circuit operates on the principle of strongly coupled electromagnetic waves. The circuit

consists of power supply rectifying unit, transmitting unit and a receiving unit. The oscillating

part of the circuit will be working on the mazzilli fly back driver principle As the circuit needs

12v dc as input supply the 230 volts AC is converted into 12v AC by using a step-down

transformer. The 15v AC from step-down transformer is given to the rectifier bridge circuit

which converts 15V AC to 15 DC. The 15v DC supply is given to the transmitting circuit. The

transmitting unit consists of two IRFZ44N Mosfets which are connected back to back. Both

the Mosfets are similar type but as no device in the nature are ideal one of the mosfet will

conduct first among the two Mosfets and the other mosfet will remain in OFF state.

The mosfet will be OFF during next cycle of operation. As this mosfet gets OFF another

mosfet gets into conduction mode and the two Mosfets get operated alternatively. As the two

Mosfets oscillates the 1.5Mhz frequency is generated in the circuit and this frequency is fed to

the bank of capacitors. The capacitors will charge and discharge periodically which results in

production of the electromagnetic waves these waves propagates with the help of the copper

loop. So the generated electromagnetic waves are transmitted to the receiver side through the

loop and air as the medium. The receiver circuit consists of the tank circuit which is in

resonance with the transmitting unit the power from the sending end will be received at the

receiving end and it will be demonstrated with the help of any load of 6watts.

For better tuning purpose a ferrite core is placed at transmitting and receiving end so that the

distance between power transmission can be improved further.

The intensity of the light at receivers end can be varied by varying the position of the receiver.

This can be explained in following cases:

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Case1: When both are parallel to each other

Case2: When one of the unit is perpendicular to other.

Case3: When both are placed beside .

4.1 Case1:

When the both transmitter are placed parallel to each other or placed to facing each other

the magnetic flux linkages will be maximum and when one of the unit brings nearer to

other unit the intensity of the light will be increased.

If one of the unit takes away from the another unit the intensity of the light decreases

because the strength of the flux linkages will be weakened.

Fig 4.1 Power transferring wirelessly to receiver

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4.2 Case2:

When the one of the unit in the two units are place perpendicular to another the power will be

not transferred to receiver unit from transmitter unit because the flux linkages will be

minimum and it will be not sufficient enough to transfer the power to receiver and hence the

light at receiver will not glow.

Fig 4.2 Power not transferring when placed perpendicularly

4.3 Case3:

When the two units are placed beside each other the power will not transfer to receiving unit

because the flux be not able to link with the receiving unit.

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Fig 4.3 Power transfer when two units placed beside each other

5.0 Applications:

WTP for space solar

Power transfer, bridging applications

For transmission purposes.

5.1 WTP for space solar:

The largest application for microwave power transmission is space solar power satellites

(SPS). In this application, solar power is captured in space and converted into electricity. The

electricity is converted into microwaves and transmitted to the earth.

The microwave power will be captured with antennas and converted into electricity. NASA is

still investigating the possibilities of SPS. One of the problems is the high investment cost due

to the space transport. The current rates on the Space Shuttle run between $7,000 and $11,000

per Kilogram of transported material.

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Fig 5.1 Solar power satellite-1

5.2 Power transfer, bridging applications :

Using a powerful focused beam in the microwave or laser range long distances can be

covered. There are two methods of wireless power transmission for bridging application. First

is the direct method, from

transmitting array to rectenna. A line of sight is needed and is therefore limited to short (< 40

km) distances. Above 40 kilometers, huge structures are needed to compensate for the

curvature of the earth.The second method is via a relay reflector between the transmitter and

rectenna. This reflector needs to be at an altitude that is visible for both transmitter and

receiver.

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5.3 Tranmission purposes:

The resistance of the wire used in the electrical grid distribution system causes a loss of 26-

30% of the energy generated. This loss implies that our present system of electrical

distribution is only 70-74% efficient. So the wireless power transmission can be used in

transmission system which increases the efficiency to a considerable amount.

6.0 Advantages of WPT:

Using this electromagnetic waves it cannot cut the human body. so the proposed wireless

power transmission system doesn’t face obstacle due to human interference.

An electrical distribution system, based on this method would eliminate the need for an

inefficient, costly, and capital intensive grid of cables, towers, and substations. The

system would reduce the cost of electrical energy used by the consumer and rid the

landscape of wires, cables, and transmission towers.

The electrical energy can be economically transmitted without wires to any terrestrial

distance, so there will be no transmission and distribution loss.

Faster rise in the demand for electrical power in the near future. These systems can only

meet these requirements with 90–94 %efficient transmission

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6.1 High Transmission Integrity and Low Loss :

To transmit wireless power to any distance without limit. It makes no difference what the

distance is. The efficiency of the transmission can be as high as 96 or 97 per cent, and there

are practically no losses.

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7.0 Demerits:

7.1 Biological Impact:

One common criticism of the Tesla wireless power system is regarding its possible

biological effects. Calculating the circulating reactive power, it was found that the frequency

is very small and such a frequency is very biologically compatible.

A general public perception that microwaves are harmful has been a major obstacle for

the acceptance of power transmission with microwaves. A major concern is that the long-

term exposure to low levels of microwaves might be unsafe and even could cause cancer.

A clearly relevant bio-effect is the effect of microwave radiation on birds, the so-called

"fried bird effect".

7.2 Economic Impact:

The concept looks to be costly initially.

For the very short range (1-10 meters), preliminary demonstrations of WTP at low power

levels (less than 1 kW) were in general quite costly.

8.0 Conclusions:

The proposed system of wireless power is the prototype for the wireless power

transmission carried out by Nicholas tesla.

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Using the tesla`s principle the wireless power transmission is demonstrated using the

strongly coupled electromagnetic waves.

The distance of power transmission can be increased further by using the components of

higher values.

9.0 Future Scope &improvements:

The research on wireless power transmission is still carrying out by NASA and The solar

power satellite is expected to realize around 2030.

Fig 9.0 Solar power satellite-2

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A typical amplitude taper is called 10 dB Gaussian in which the power density in the

center of the transmitting antenna is ten times larger than that on the edge of the

transmitting antenna is building.

10.0 Bibliography:

www.teslacoil.it

www.4hv.org

http://www.nss.org/settlement/ssp/index.htm

www.california university.com

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