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4 'Problems With Conventional Methods 'Emergence Of CEET 'Different Ways Of Energy Transfer 'Inductive Power Transfer 'Working Principle 'Model Of Magnetic System 'Simulation results 'Applications 'Design methodology 'Methods Of Improving Efficiency 'References

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' Wear and tear on electrical s ' Exposure to environmental problems ' Around 23% of transmission and distribution losses

Also the technology for alternative sources of energy like solar, wind etc are still considered costly.

r rr ' In 1996, Auckland Uniservices developed an Electric Bus power system using electrodynamic induction and Prof. John Boys Team commissioned 1st commercial IPT Bus in New Zealand. ' Prof. Marin Solacic, at MIT, wirelessly powered a 60W light bulb with 40% efficiency at 2 meters with two 60 cm-diameter coils.

ÿ r 4 ' Transmission of electrical energy from a power source to an electrical load without interconnecting wires ' Large amount of power transmitted is received ' Closely related to optimization of transferable power, efficiency and heat development ' Elimination of cables, slip rings, plugs and sockets, increasing reliability ' Maintenance free operation

ÿr 1. Electromagnetic induction A) Electrodynamic induction method B) Electrostatic induction method 2. Electromagnetic radiation A) Microwave method B) Laser method 3. Electrical conduction

r 4 r ' This 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. ' Electric current flowing through a primary coil creates a magnetic field that acts on a secondary coil producing a current within it. ' Inductive coupling allows power transfer from few mW up to hundred KW

r 4 ' Electrostatic or capacitive coupling is the age of electrical energy through a dielectric ' The capacitive coupling is used in low power range (sensor supply systems) ' The electric field is created by an alternating current of high potential and high frequency

r ' More directional power transmission via radio waves, allowing longer distance power beaming, with shorter wavelengths of electromagnetic radiation. ' A rectenna is used to convert the microwave energy back into electricity having efficiency greater than 95%

j ' Closer to visible region of spectrum (10s of microns (um) to 10s of nm) ' Power can be transmitted by converting electricity into a laser beam that is then pointed at a solar cell receiver ' Also known as power beaming

ë ' no radio-frequency interference to existing radio communication ' control of access; only receivers illuminated by the laser receive power ' compact size of solid state lasers

' Conversion to light, such as with a laser, is inefficient. ' Conversion back into electricity is inefficient, with photovoltaic cells achieving 40%-50% efficiency ' Atmospheric absorption causes losses. ' As with microwave beaming, this method requires a direct line of sight with the target

r ' Actual displacement of charge through earth and atmosphere. ' Low frequency alternating current transmitted through earth with low loss because the net resistance of earth is less than 1 ohm. ' Electrical conduction through atmospheric strata is made possible by the creation of discharge plasma through the process of atmospheric ionization.

ÿ ! 4! ' Consists of magnetically coupled transmitter coil L1 and a receiver coil L2 ' Alternating current in transmitter coil generates magnetic field inducing voltage in the receiver coil ' Efficiency depends on the coupling (k) between the inductors and their quality (Q)



The inductances L(h), L1 and L2 can be obtained by means of a magnetic flux simulation. The inductances can be calculated as described in the following equations:

L(h): main inductance R1, R2: ohmic resistances R(L): secondary load resistance L1, L2: leakage inductances

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' Powering the Home ' Wireless Charging ' Defence ' Space based Solar Power ' Transport

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j Realized by a parallel resonance capacitor or series resonance capacitor at secondary coil

Use Of ferrite cores

' improves the magnetic characteristics. ' Increases transferable electrical power and efficiency

Thus we have seen that wireless energy transmission has improvements over the conventional ones. An efficiency greater than 90 % can be realized by using this system. A lot of study is being done in this field. It finds application in many fields like spacecraft propulsion, battery charging and defence. Thus this technology used in combination with the conventional methods can lead to an effective and efficient system.

° 'Modelling and design of a less energy transfer system for a notebook battery charger Pascal Meyer, Paolo Germano and Yves Perriard 'Eßer, A.; Nagel, A.: less high speed signal transmission integrated in a compact rotatable power 'transformer. European Conference on Power Electronics and Applications, Brighton 1993, Vol. 4, pp 409-414 'Green, A. W.; Boys, J. T.: 10 kHz inductively coupled power transmission ± concept and control. 'International Conference on Power Electronics and Variable Speed Drives, London 1994, pp 694-699 'Knaup, P.; Hasse, K.: Zero voltage switching converter for magnetic transfer of energy to movable systems. 'Hayes, J. G.; Hall, J. T.; Bellino, G.; Conroy, K.: Off-board incuctive charging for the Genaral Motors EV1electric vehicle.