Energy Contactless Transfer System

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Index

Problems With Conventional Methods

Emergence Of CEET

Different Ways Of Energy Transfer

Inductive Power Transfer

Working Principle

Model Of Magnetic System

Simulation results

Applications

Methods Of Improving Efficiency

References


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Problems associated with the conventional

methods

Results in greenhouse gases and pollute environment

Wear and tear on electrical contactsExposure 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.


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Emergence ofCEET

In 1996, Auckland Uniservices developed an Electric Bus power

system using electrodynamic induction and Prof. John Boys Teamcommissioned 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.


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What Contactless EnergyTransmission Is

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


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Different Ways ofEnergyTransfer

1. Electromagnetic induction

A) Electrodynamic induction method

B) Electrostatic induction method

2. Electromagnetic radiation

A) Microwave method

B) Laser method

3. Electrical conduction


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Electromagnetic Induction

Electrodynamicinduction method

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 dooccur. 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 tohundred KW


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Electrostatic Induction Method

Electrostatic or capacitive coupling is the passage of

electrical energy through a dielectric

The capacitive coupling is used in low power range (sensorsupply systems)

The electric field is created by an alternating current of high

potential and high frequency


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Electromagneticradiation

Microwave method

More directional power transmission via radio waves, allowinglonger 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%


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Lasermethod

Closer to visible region of spectrum (10s of microns (um) to 10s ofnm)

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

Advantages

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


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Disadvantages

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


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Electrical Conduction

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.

The electrical displacement is also by means of electrostatic induction

Electrical conduction through atmospheric strata is made possible by

the creation of discharge plasma through the process of atmospheric

ionization.


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WorkingPrinciple Of IPT

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)


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Model OfMagnetic System


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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 thefollowing equations:

L(h): main inductance

R1, R2: ohmic resistances

R(L): secondary load

resistance

L1, L2: leakage inductances


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Observations from results

Maximum output power

depends on:square of the primary

magneto motive force,

the main inductance

transmission frequency


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Applications

Powering the Home

Wireless Charging

Defence

Space based Solar Power

Transport


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Portable phone battery Charger


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Methods ofimproving efficiency

Leakage inductance compensation method

Realized by a parallel resonance capacitor or seriesresonance capacitor at secondary coil

Resonance capacitor is independent of secondary load

resistance given by 1/(L1+L20)(N2*N2)(w*w)


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Use Of ferrite cores

improves the magnetic

characteristics.

Increases transferable

electrical power and

efficiency


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Conclusion

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 donein 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.


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References

Eer, A.; Nagel, A.: Contactless 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.

European Conference on Power Electronics and Applications,Trondheim 1997, Vol. 2, pp 168-173

Hayes, J. G.; Hall, J. T.; Bellino, G.; Conroy, K.: Off-board incuctive

charging for the Genaral Motors EV1electric vehicle.


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Documents

Energy Contactless Transfer System