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REVIEW WIRELESS ELECTRIC ENERGY TRANSMISSION THROUGH RESONANCE OR MAGNETIC COUPLING _WITRICITY_

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REVIEW WIRELESS ELECTRIC ENERGY TRANSMISSION THROUGH RESONANCE OR MAGNETIC COUPLING _WITRICITY_ Powered By Docstoc
					  International Journal of Electrical Engineering OF ELECTRICAL ENGINEERING
INTERNATIONAL JOURNAL and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN &
  0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME
                                    TECHNOLOGY (IJEET)

ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
                                                                                    IJEET
Volume 3, Issue 3, October - December (2012), pp. 43-51
© IAEME: www.iaeme.com/ijeet.asp                                                ©IAEME
Journal Impact Factor (2012): 3.2031 (Calculated by GISI)
www.jifactor.com



      REVIEW WIRELESS ELECTRIC ENERGY TRANSMISSION
   THROUGH RESONANCE OR MAGNETIC COUPLING (WITRICITY)

  Dipak A. Mhaske                                 Prof. S.S. Katariya
  Electronics Department,                         Asst. Prof. Electronics Department,
  Amrutvahini College of Engineering, Sangamner   Amrutvahini College of Engineering, Sangamner
  dipak_mhaske85@yahoo.co.in                      nileshpatni@indiatimes.com


  ABSTRACT

  Imagine the world use electricity wirelessly by using any antenna or different technology will
  be a great advantage in terms of human beings. It is indeed low cost system or free of charge
  and can be used in safe mode since the Human Life becomes easier. Therefore, in this project
  an application will be implemented and developed for different power hungry devices by
  using Resonance Frequency. The system is constructed by integrating hardware and.

  I.      INTRODUCTION
          In this era of modernization, electricity has become the cup of life. A moment without
  electricity makes your thinking go dry. The major source of conventional form of electricity
  is through wires. The continuous research and development has brought forward a major
  breakthrough, which provides electricity without the medium of wires. This wonder baby is
  called WiTricity.
          There are certain small but very useful discoveries made in history, which changed
  the world for ever, Newton’s gravitational law, Watt’s steam engine, Thomson’s bulb and
  many more. But a renaissance occurred with the invention of Electromagnetic Waves by
  Maxwell. Sir Jagdish Chandra Bose successfully generated electromagnetic waves having
  wavelength in the range of 5mm to 25 mm. Thereafter an Italian scientist named Marconi
  succeeded in transmitting electromagnetic waves up to a distance of several miles. And with
  this there started a new era called WIRELESS TECHNOLOGY. Today, as we can see the
  word ‘wireless’ is common in day – to – day life. Wireless communication has made the
  world smaller. Almost each and everything is wireless or cordless. Cordless mouse, cordless
  keyboard, satellite communication, mobiles, cordless microphones and headphones, wireless
  internet service i.e. WI-FI, etc. And these have definitely increased the standard of living.
          In fact it dates back to the 19th century, when Nikola Tesla used conduction-
  based systems instead of resonance magnetic fields to transfer wireless power. As it is
  in Radiative mode, most of the Power was wasted and has less efficiency. Further, in 2005,
  Dave Gerding coined the term WiTricity which is being used by the MIT researchers
  today.


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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME

        Moreover, we all are aware of the use of electromagnetic radiation (radio
waves) which is quite well known for wireless transfer of information. In addition,
lasers have also been used to transmit energy without wires. However, radio waves are
not feasible for power transmissions because the nature of the radiation is such that it spreads
across the place, resulting into a large amount of radiations being wasted. And in the case
of lasers, apart from requirement of uninterrupted line of sight (obstacles hinders the
transmission process). It is also very dangerous.

II. NEED OF WITRICITY

        WiTricity is nothing but wireless electricity. Transmission of electrical energy from
one object to another without the use of wires is called as WiTricity. WiTricity will ensure
that the cell phones, laptops, iPods and other power hungry devices get charged on their own,
eliminating the need of plugging them in. Even better, because of WiTricity some of the
devices won't require batteries to operate.
        Imagine a future in which wireless power transfer is feasible: cell phones, household
robots, mp3 players, laptop computers, and other portable electronics capable of charging
themselves without ever being plugged in, freeing us from that final, ubiquitous power wire.
Some of these devices might not even need their bulky batteries to operate.

III. DIFFERENT TERMS FOR WITRICITY

A. The Possibility of Energy Transfer via Coupled Magnetic Resonances
        Resonance phenomenon is widely existed in nature. Different kind of resonance
contains different kind of energy. The sound of tuning fork is produced by resonance and the
earthquake is also produced by resonance, while the energy of earthquake is much higher
than the sound of tuning fork. Resonance is a trend that one physical system in its natural
frequency tends to absorb more energy from the environment. In other words, it is a
phenomenon that one object vibrates which cause the other one with the same frequency
vibrates. Resonances can transfer energy. There is a simple example: when two tuning forks
A and B with the same frequency are placed not far apart, hit fork A to make it phonating,
when we hold fork A to stop its phonation, we find that fork B without hitting is phonating.
        Frequency in it, the electromagnetic resonance is generating, energy in the inductance
coil continues gathering, the voltage is increasing, and the receiving energy can be used by
the load after being converted by follow-up circuits. Generally speaking, electromagnetic
systems with same resonance frequency are weak couplings apart in a certain distance. Two
systems with same inherent resonance frequency will generate strong magnetic resonance and
form a magnetic resonances system. If there are more than two resonators in effective range,
they can also join the resonances system. One resonator can be connected with continuously
power supply to serve as the energy source and others consume the energy, so the energy
transfer system realized. In other words, we can transfer energy from one place to another via
invisible magnetic field instead of the visible electrical wires.
        Magnetically coupled resonators used for wireless power transfer have shown the
potential to deliver power with more efficiency than far-field approaches, and at longer
ranges then traditional inductively coupled schemes. However, this prior work is limited to a
fixed distance and orientation, with efficiency falling off rapidly when the receiver is moved
away from its optimal operating point.
In this work, we extend prior analysis of coupled magnetic resonance to elucidate several key
system concepts including frequency splitting, critical coupling, and impedance matching.


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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME




       Fig. 1 Sketch Of The Magnetically Coupled Resonance Wireless Power System

    We present a model of magnetically coupled resonators in terms of passive circuit
elements and derive system optimization parameters. Additionally, a method for
automatically tuning the wireless power system is demonstrated, so that the maximum
possible transfer efficiency is obtained for nearly any distance and/or orientation as long as
the receiver is within the working range of the transmitter. This is important from a practical
standpoint because in many applications, such as laptop recharging, the range and orientation
of the receive device with respect to the transmit device varies with user behaviour. [1]


B. WiTricity Technology: The Basics
        Understanding What WiTricity technology is transferring electric energy or power
over distance without wires is quite simple. Understanding how it works is a bit more
involved. We’ll start with the basics of electricity and magnetism, and work our way up to
the WiTricity technology [2].
Magnetism:-
        A fundamental force of nature, which causes certain types of materials to attract or
repel each other. Permanent magnets, like the one on your refrigerator and the earth’s
magnetic field, are examples of objects having constant magnetic fields. Oscillating magnetic
fields vary with time, and can be generated by alternating current (AC) flowing on a wire.
The strength, direction, and extent of magnetic fields are often represented and visualized by
drawings of the magnetic field lines[2].




                  Fig. 2 Illustration Representing The Earth’s Magnetic Field

Electromagnetism:-
         A term for the interdependence of time-varying electric and magnetic fields. For
example, it turns out that an oscillating magnetic field produces an electric field and an
oscillating electric field produces a magnetic field.




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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME




                  Fig. 3 Illustration Representing the Electro Magnetic Field
        As electric current, I, flows in a wire, it gives rise to a magnetic field, B, which wraps
around the wire. When the current reverses direction, the magnetic field also reverses its
direction [2].

Energy/Power Coupling:-
        Energy coupling occurs when an energy source has a means of transferring energy to
another object. One simple example is a locomotive pulling a train car the mechanical
coupling between the two enables the locomotive to pull the train, and overcome the forces of
friction and inertia that keep the train still and, the train moves. Magnetic coupling occurs
when the magnetic field of one object interacts with a second object and induces an electric
current in or on that object. In this way, electric energy can be transferred from a power
source to a powered device. In contrast to the example of mechanical coupling given for the
train, magnetic coupling does not require any physical contact between the object generating
the energy and the object receiving or capturing that energy.




                           Fig. 4 Schematic Energy / Power Coupling

       An electric transformer is a device that uses magnetic induction to transfer energy
from its primary winding to its secondary winding, without the windings being connected to
each other. It is used to “transform” AC current at one voltage to AC current at a different
voltage[2].

Resonant Magnetic Coupling:-
        Magnetic coupling occurs when two objects exchange energy through their varying or
oscillating magnetic fields. Resonant coupling occurs when the natural frequencies of the two
objects are approximately the same.




                         Fig. 5 Two Idealized Resonant Magnetic Coils

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   International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
   0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME

           Two idealized resonant magnetic coils, shown in yellow. The blue and red color
   bands illustrate their magnetic fields. The coupling of their respective magnetic fields is
   indicated by the connection of the color bands [7].

    WiTricity Technology -
          WiTricity power sources and capture devices are specially designed magnetic
   resonators that efficiently transfer power over large distances via the magnetic near-field.
   These proprietary source and device designs and the electronic systems that control them
   support efficient energy transfer over distances that are many times the size of the
   sources/devices themselves.
          The WiTricity power source, left, is connected to AC power. The blue lines represent
   the magnetic near field induced by the power source. The yellow lines represent the flow of
   energy from the source to the WiTricity capture coil, which is shown powering a light bulb.
   Note that this diagram also shows how the magnetic field (blue lines) can wrap around a
   conductive obstacle between the power source and the capture device [2].




                                      Fig. 6 WiTricity Technology

   IV. SYSTEM OVERVIEW

3.4 A. Energy Transfer System Via Coupled Magnetic Resonance –




        Fig. 7 Block Diagram of Energy Transfer System Via Coupled Magnetic Resonance

        As shown in figure, a simple structure of energy transfer system via coupled magnetic
   resonance is proposed. The energy supply of source is provided by power convert module,
   inductor Ls and capacitor Cs constitute a resonance source circuit to generate an alternative
   non-radiative magnetic field. The resonance frequency of LC circuit is f s . The control signal
   for power switch tube T is generated by switch drive circuit, and its frequency is f k . In
   theory, when f t is close or equal to f s , the oscillation of source resonance circuit is strongest,
   the value of resonance current is highest, and the magnetic field intensity is also strongest.
   Inductor L t and capacitor C t constitute the receiving resonance circuit to produce resonance
   with the magnetic field which generated by source resonance circuit to receive energy. The

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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME

frequency of receiving resonance circuit is f t , the parameters of L t and C t needn’t be in full
accord with the source resonance circuit. What the receiving resonance circuit must need is to
ensure fs = f t , that is the necessary condition for energy transfer.

B. Circuit Representation Of A Resonant Coupled System With A Single Load




Fig. 8 A Schematic Circuit Drawing Of A Source Coil Pair and A Signal-Receiving Coil Pair.
Each Load In Multiple Receiver System Involves A Receiving Coil Pair.

        Fig.8 shows a schematic circuit representation of a system like the experimental
system shown in above figure, but with only a single load coil pair. We use this system to
develop an understanding of the resonant coupling mechanism and to serve as a basis for
extending it to multiple receivers. In the single receiver system of Fig. 8, the source drives a
large single-turn coil, labelled L1 that is inductively coupled to a large multi turn resonant coil
L2 of the same diameter. The small resonant coil L3 is inductively coupled to a small coil of
the same diameter, labelled L4, that is terminated by a load element. Lumped capacitors C2
and C3 respectively terminate the resonant coils L2 and L3. The resistances R1, R2, R3, and R4
are the small resistances of the coils themselves, while RS is the internal resistance of the
source, and RL is the load resistance.
        The two identical open-circuited “self-resonant” coils, with a resonant frequency
based upon the distributed inductance and distributed capacitance of each coil. Here, with
completely different source and receiver coils, the lumped capacitances are chosen so as to
yield identical resonant frequencies,
                                                1         1
                                          =         =

       This alteration provides a simple means to achieve resonant coupling between a large
source coil and one or several small receiving coils [3].

V SYSTEM ANALYSIS

A. Circuit Analysis
        A circuit model for the experimental setup with only one receiving coil pair driving a
single load, as represented in Fig.7 is based upon the application of Kirchhoff’s voltage law
around each of the four loops. The voltage at the terminals of each coil is described as the
time rate of change of flux linkage. Λ1 through Λ4 and i1 through i4 represent complex
amplitudes of flux linkages and currents in each of the four coils; VS represents the complex


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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME

amplitude of the ideal voltage source. With resistances R1 through R4, RS, and RL, and
capacitances C2 and C3, the circuit constraints at frequency ω are
                           =       +      + + Λ …………… 1
                           0=         +        +      Λ   …………… 2

                           0=         +        +      Λ   …………… 3
                            0=      +        + Λ …………… 4
        Since each of the four coils is inductively coupled to the other three, the flux linkages
are related to the currents by a symmetric 4 × 4 inductance matrix:




                                        …………..(5)
        For a known ideal source voltage VS and known resistances, capacitances, and self
inductances and mutual inductances, (1) to (4), with (5) substituted for the flux linkages,
comprise four simultaneous equations that determine the currents i1 through i4 , and thus the
complex amplitude of the load voltage VL = −RL i4 . Since the system is linear, this analysis
determines the transfer function based upon the source frequency, |(VL/VS )(ω)|.
        Extension of the circuit model to multiple loads, as for the experimental two-load
system straightforward, with six equations replacing four. More generally, extension to an
arbitrary number of loads. The use of a circuit model here is appropriate because, as
described in, the interaction involves magneto quasistatic field structures. Equivalently, we
can compare radiated electromagnetic power with power dissipated in the resistances of the
circuit model. The radiation resistance Rr of a coil with N turns and radius a, at source
frequency f and corresponding free space wavelength λ = c/f
where c = 3.00 × 108 m/s is
                                           2
                                       =
Coil 2, then has the largest radiation resistance, with value Rr2 = 8.7 × 10−4 , which is far
too small in comparison with the ohmic resistance R2 to be significant. Unintended magnetic
coupling with nearby objects is of far less significance than it would be at higher frequencies,
with wavelengths on the scale of the transmitting coil. [3]

B. Comparative Study of Different Energy or Power Transfer System
1. Laser Beam
       The laser beam is a coherent light beam capable to transport very high energies that
makes it an efficient mechanism to transfer energy point to point using a line of sight.
2. Radio waves and Microwaves
       It can be seen an scheme to transmit high power energy through long distances using
Microwaves. Besides, there is a whole research field in the rectenna area which are antennas
capable to collect energy from radio waves.

3. Inductive Coupling
       The inductive coupling works on the resonant coupling effect between the coils of
two LC circuits. Maximum efficiency can only be reached when the transmitter and the
receiver are placed in a very short distance.


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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME

4. Strong Electromagnetic Resonance
 In a wireless energy transfer method was introduced, this method uses the strong
electromagnetic resonance phenomenon, achieving energy transfer in an efficient way
through several tens of centimetres

5. Health Effects Due To the Electromagnetic Waves
        The result of radio frequencies flowing everywhere is the dispersion of the
electromagnetic waves. People are getting more concerned about the effects caused by the
electromagnetic radiation generated every day.
        To this concern one more effect should be added by the wireless energy transfer
mechanism, because it is based on electromagnetic waves. Several studies have been
performed on the effects of the electromagnetic waves, in particular the cellular phone waves,
verifying that on the fringe of the international safety values certain effects on the genes are
noticed. In ensures that it is not yet possible to establish health effects in the short or long
term due to the electromagnetic waves exposure like the ones generated by broadcasting
stations and cellular phone stations.
        Some studies reveal that there are harmful effects on humans, but these effects occur
on high frequencies (>800 MHz), therefore there are no health concerns for the experiment.

6. Electric Resonance
         Electromagnetic radiation has been used, typically, for information broadcasting. But
that is not the only possible application, however. In particular, using microwaves the energy
can be directed to an specific point. Although the method is efficient, it has two draw-backs:
requires a sight line and it is a dangerous mechanism for live beings. [4]

VI. CONCLUSION
        This paper disclosed that witricity power application not much operate at full
efficiency. The potential applications of witricity are expected to materialize in the new
future, of say a few years’ time, after the necessary modifications are to them. These witricity
applications are expected to work on the gadgets that are in close proximity to a source of
wireless power where in the gadget charges automatically without necessarily having to get
plugged in. There are no limitations in witricity power application where anything and
everything that used to run with batteries or electrical connections can be used using
witricity. Just imagine, the future witricity power application permit you to use wireless
energy, without having to replace or recharge batteries either or of remembering to recharge
batteries periodically. In addition to this, with witricity, there is no need of plugging in any
wires and plugs and thus face a mess of wires.


REFERENCES

[1] Alanson P. Sample, David T. Meyer, and Joshua R. Smith, “Analysis, Experimental
    Results, and Range Adaptation of Magnetically Coupled Resonators for Wireless Power
    Transfer” Downloaded on June 04,2010 at 17:09:09 UTC from IEEE Xplore.
[2] http://www.witricity.com/pages/technology.html
[3] Benjamin L. Cannon, James F. Hoburg, Daniel D. Stancil, and Seth Copen Goldstein,
    “Magnetic Resonant Coupling As a Potential Means for Wireless Power Transfer to
    Multiple Small Receivers” IEEE TRANSACTIONS ON POWER ELECTRONICS,
    VOL. 24, NO. 7, JULY 2009


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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN
0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME

[4] J.A. Ricaño Herrera, H. Rodríguez Torres, H. Vázquez Leal and A. Gallardo del Angel
    “Experiment About Wireless Energy Transfer” 1St International Congress on
    Instrumentation and Applied Sciences


                      Dipak A. Mhaske has completed his B.E. (Electronics) & currently
                      appear to M.E. (Electronics) in Amrutvahini College of Engineering,
                      Sangamner. Dist.- Ahmednagar, Maharashtra, India. He is working as
                      Lecturer in Electronics Department, Pravara Rural Engineering College,
                      Loni, Maharashtra, India.



                        Prof. Shraddha S. Katariya             (Patni), has completed her
                        M.E.(Electronics) & B.E. (E& TC), Member of IEEE & ISTE. She is
                        working as a Assistant Professor in Electronics Department,
                        Amrutvahini College Of Engineering, Sangamner, Dist. Ahmednagar,
                        Maharashtra, India. Prof Katariya has teaching experience of 13 years
                        to Undergraduate, Graduate & Post Graduate Students. Prof S S
                        Katariya has Published 04 papers in International Journal, 02 papers in
                        National Journal & presented 02 papers in International Conference &
                        13 papers in National Conferences.




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