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

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1 INTERNATIONAL International Journal of Electrical JOURNAL Engineering and OF Technology ELECTRICAL (IJEET), ISSN 0976 ENGINEERING 6545(Print), ISSN & TECHNOLOGY (IJEET) ISSN (Print) ISSN (Online) Volume 3, Issue 3, October - December (2012), pp IAEME: Journal Impact Factor (2012): (Calculated by GISI) IJEET I A E M E REVIEW WIRELESS ELECTRIC ENERGY TRANSMISSION THROUGH RESONANCE OR MAGNETIC COUPLING (WITRICITY) Dipak A. Mhaske Electronics Department, Amrutvahini College of Engineering, Sangamner dipak_mhaske85@yahoo.co.in Prof. S.S. Katariya Asst. Prof. Electronics Department, Amrutvahini College of Engineering, Sangamner 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 conductionbased 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. 43

2 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. 44

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

3 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. 45

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.

Energy/Power Coupling:- Energy coupling occurs when an energy source has a means of transferring energy to another object.

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.

4 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 46

5 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]. IV. SYSTEM OVERVIEW Fig. 6 WiTricity Technology 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 47

6 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 L 1 that is inductively coupled to a large multi turn resonant coil L2 of the same diameter. The small resonant coil L 3 is inductively coupled to a small coil of the same diameter, labelled L 4, that is terminated by a load element. Lumped capacitors C 2 and C 3 respectively terminate the resonant coils L 2 and L 3. The resistances R 1, R 2, R 3, and R 4 are the small resistances of the coils themselves, while R S is the internal resistance of the source, and R L 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. Λ 1 through Λ 4 and i 1 through i 4 represent complex amplitudes of flux linkages and currents in each of the four coils; V S represents the complex 48

7 amplitude of the ideal voltage source. With resistances R 1 through R 4, R S, and R L, and capacitances C 2 and C 3, 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 V S 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 i 1 through i 4, and thus the complex amplitude of the load voltage V L = R L i 4. Since the system is linear, this analysis determines the transfer function based upon the source frequency, (V L /V S )(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 = m/s is = 2 Coil 2, then has the largest radiation resistance, with value Rr2 = Ω, 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. 49

8 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] [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

9 [4] J.A. Ricaño Herrera, H. Rodríguez Torres, H. Vázquez Leal and A. Gallardo del Angel Experiment About Wireless Energy Transfer 1 St 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. 51

WITRICITY REVIEW THROUGH RESONANCE OR MAGNETIC COUPLING

WITRICITY REVIEW THROUGH RESONANCE OR MAGNETIC COUPLING Sudeep Kumar Yadav,Neeraj yadav Electronics and communication department, Dronacharya college of engineering,gurgaon Haryana,India ABSTRACT: A moment