seminar report on wireless inductive charging

1. A
Report On
INDUCTIVE CHARGING
DEPARTMENT ELECTRONICS & COMMUNICATION ENGINEERING
COLLEGE OF TECHNOLOGY AND ENGINEERING
Maharana Pratap University of Agriculture and Engineering
Udaipur (Rajasthan)
Submitted to:- Submitted By:- Mr. P.C.
Bapna Jai Lal Meena
Assistant Prof. B.E.FINAL YEAR
ECE (CTAE) ECE (CTAE)
ACKNOWLEDGEMENT

2. Before we get thick, I would like to add heartful words for the people who
helped me a lot in the completion of my seminar .I would like to give
sincere gratitude to my parents. Words are unable to express their values
in my life.
I would like to take this opportunity to express my honors, respect, deep
gratitude & Regards to my guide Mr. P.C. Bapna sir, without whom help
this seminar would not have been success. Also giving me all the support &
cooperation required & for being tremendous source of my inspiration &
motivation.
I will be failing in my duty, if I do not my express my gratitude towards
other staff members and friends who have helped me to complete my
seminar work successfully and in time.
Yours Faithfully
ABSTRACT

3. An inductive charging system for vehicle battery chargers includes a
transformer having a stationary primary coil and a secondary coil mounted
on the vehicle. The primary coil is mounted in a charging station and has a
power source connected therewith. When the vehicle is parked adjacent to
the charging station, the secondary coil on the vehicle is proximate to the
primary coil in the station. The power source is activated to deliver current
to the primary coil which generates a magnetic field to induce a voltage in
the secondary coil. A controller is connected with the power source to
adjust the voltage delivered to the primary coil. A feedback loop between
the secondary coil and the controller delivers a secondary voltage signal to
the controller which continuously adjusts the power source in order to
maintain the secondary output voltage at a predetermined value.
INDEX
1. Introduction
2. History
3. Terminology
3.1 DC/AC converter
3.2 Split-core transformer
3.3 Transmitting inductor
3.4 Receiving inductor
3.5 Rectifier and filter

4. 3.6 Voltage regulation
4. How ordinary charger work
5 How inductive charger work
6. Advantage
7. disadvantage
8. Use area of inductive charging
8.1 Electric car
8.2 Artificial heart
8.3 Mobile charger
8.4 Toothbrush
8.5 Power Mats
9. Refrence
Introduction
A transformer can be used to induce a current from one circuit to another
nearby circuit, due to the mutual inductance of the two circuits. The coil
carrying the power is called the primary, and the other coil is the
secondary. Current flows through the primary inductive coil and the
resulting magnetic flux induces an alternating current through the magnetic
field and across the secondary coil, completing the circuit. When applied to
a transformer the primary and secondary coils are fixed in relation to one
another. Using these electromagnetic properties, and patents leased by
Dr. John Boys of the University of Auckland, Wampfler®
has developed an
inductive charging system that can be used to charge a range of different
devices. Some of the current applications of this system include the

5. powering of a floor conveying system at both an Audi and a BMW engine
assembly line, three sorting system distribution centers located in Europe,
and an outdoor elevator in Germany.
The major aim of this project is to test how the orientation of the primary
and secondary coils affects the charging rate of the batteries. The two
most important aspects of the design include a frame capable of supporting
the secondary coil in a range of orientations above the primary coil, and a
positioning system capable of accurately measuring what that orientation
is. This frame will simulate the underside of the bus carrying the secondary
coil. The data obtained from running these experiments will help determine
the tolerances in which the bus must be aligned with the primary coil to
obtain a sufficient charge for the bus within a given time frame.
Problem Statement
The Inductive Charging team has been tasked with developing and
implementing a method in which to determine the sensitivity of the charging
rate of the Inductive Power Transfer system, to the orientation of the
primary and secondary coils.

6. History
Wireless power transmission is not a new idea. Nicola Tesla demonstrated
transmission of electrical energy without wires in early 20th century. Tesla
used electromagnetic induction systems. Tesla discovered that electrical
energy could be transmitted through the earth and the atmosphere. In the
course of his research he successfully lit lamps at moderate distances and
was able to detect the transmitted energy at much greater distances. The
Wardenclyffe Tower project was a commercial venture for trans-Atlantic

7. wireless telephony and proof-of-concept demonstrations of global wireless
power transmission. The facility was not completed because of insufficient
funding. Earth is a naturally conducting body and forms one conductor of
the system. A second path is established through the upper troposphere
and lower stratosphere starting at an elevation of approximately 4.5 miles.
A global system for "the transmission of electrical energy without wires"
called the World Wireless System, dependent upon the high electrical
conductivity of plasma and the high electrical conductivity of the earth, was
proposed as early as 1904
Following World War II, which saw the development of high-power
microwave emitters known as cavity magnetrons, the idea of using
microwaves to transmit power was researched.
William C Brown demonstrated a microwave powered model helicopter in
1964. This receives all the power needed for flight from a microwave beam.
In 1975 Bill Brown transmitted 30kW power over a distance of 1 mile at
84% efficiency without using cables. Japanese researcher Hidetsugu Yagi
also investigated wireless energy transmission using a directional array
antenna that he designed. In February 1926, Yagi and Uda published their
first paper on the tuned high-gain directional array now known as the Yagi
antenna. While it did not prove to be particularly useful for power
transmission, this beam antenna has been widely adopted throughout the
broadcasting and wireless telecommunications industries due to its
excellent performance characteristics.
In 2006, more recent breakthroughs were made; using electrodynamics
induction a physics research group, led by Prof. Marin Soljacic, at MIT,
wirelessly power a 60W light bulb with 40% efficiency at a 2 meters
distance with two 60 cm-diameter coils.
Researchers developed several techniques for moving electricity over long
distance without wires. Some exist only as theories or prototypes, but
others are already in use.

8. TERMINOLOGY
Full-wave rectification
A full-wave rectifier converts the whole of the input waveform to one of
constant polarity (positive or negative) at its output. Full-wave rectification
converts both polarities of the input waveform to DC (direct current), and
yields a higher mean output voltage. Two diodes and a center
tapped transformer, or four diodes in a bridge configuration and any AC
source (including a transformer without center tap), are needed. Single
semiconductor diodes, double diodes with common cathode or common
anode, and four-diode bridges, are manufactured as single components.

9. For single-phase AC, if the transformer is center-tapped, then two diodes
back-to-back (cathode-to-cathode or anode-to-anode, depending upon
output polarity required) can form a full-wave rectifier. Twice as many turns
are required on the transformer secondary to obtain the same output
voltage than for a bridge rectifier, but the power rating is unchanged.
The average and root-mean-square no-load output voltages of an ideal
single-phase full-wave rectifier are:
A very common double-diode rectifier tube contained a single
common cathode and two anodes inside a single envelope, achieving full-
wave rectification with positive output. The 5U4 and 5Y3 were popular
examples of this configuration.
Power inverters
A power inverter, or inverter, is an electrical power converter that
changes direct current (DC) to alternating current (AC); the converted AC
can be at any required voltage and frequency with the use of appropriate
transformers, switching, and control circuits.

10. Working principle
The single-phase voltage source half-bridge inverters, are meant for lower
voltage applications and are commonly used in power supplies .Figure
shows the circuit schematic of this inverter.
Low-order current harmonics get injected back to the source voltage by the
operation of the inverter. This means that two large capacitors are needed
for filtering purposes in this design. As Figure , only one switch can be on
at time in each leg of the inverter. If both switches in a leg were on at the
same time, the DC source will be shorted out.
Inverters can use several modulation techniques to control their switching
schemes. The carrier-based PWM technique compares the AC output
waveform, vc, to a carrier voltage signal, vΔ. When vc is greater than vΔ, S+
is on, and when vc is less than vΔ, S- is on. When the AC output is at
frequency fc with its amplitude at vc, and the triangular carrier signal is at
frequency fΔ with its amplitude at vΔ, the PWM becomes a special

11. sinusoidal case of the carrier based PWM.This case is dubbed sinusoidal
pulse-width modulation (SPWM).For this, the modulation index, or
amplitude-modulation ratio, is defined as ma = vc / v∆ .
The normalized carrier frequency, or frequency-modulation ratio, is
calculated using the equation mf = f∆ / fc .
If the over-modulation region, ma, exceeds one, a higher fundamental AC
output voltage will be observed, but at the cost of saturation. For SPWM,
the harmonics of the output waveform are at well-defined frequencies and
amplitudes. This simplifies the design of the filtering components needed
for the low-order current harmonic injection from the operation of the
inverter. The maximum output amplitude in this mode of operation is half of
the source voltage. If the maximum output amplitude, ma, exceeds 3.24,
the output waveform of the inverter becomes a square wave.
As was true for PWM, both switches in a leg for square wave modulation
cannot be turned on at the same time, as this would cause a short across
the voltage source. The switching scheme requires that both S+ and S- be
on for a half cycle of the AC output period.The fundamental AC output
amplitude is equal to vo1 = vaN. .
Its harmonics have an amplitude of voh =vo1 / h.
Therefore, the AC output voltage is not controlled by the inverter, but rather
by the magnitude of the DC input voltage of the inverter.
Using selective harmonic elimination (SHE) as a modulation technique
allows the switching of the inverter to selectively eliminate intrinsic
harmonics. The fundamental component of the AC output voltage can also
be adjusted within a desirable range. Since the AC output voltage obtained
from this modulation technique has odd half and odd quarter wave
symmetry, even harmonics do not exist. Any undesirable odd (N-1) intrinsic
harmonics from the output waveform can be eliminated.

12. Used Transformer:-
The construction of a simple two-winding transformer consists of each
winding being wound on a separate limb or core of the soft iron form which
provides the necessary magnetic circuit. This magnetic circuit, know more
commonly as the "transformer core" is designed to provide a path for the
magnetic field to flow around, which is necessary for induction of the
voltage between the two windings.
However, this type of transformer construction were the two windings are
wound on separate limbs is not very efficient since the primary and
secondary windings are well separated from each other. This results in a
low magnetic coupling between the two windings as well as large amounts
of magnetic flux leakage from the transformer itself. But as well as this "O"
shapes construction, there are different types of "transformer construction"
and designs available which are used to overcome these inefficiencies
producing a smaller more compact transformer.
The efficiency of a simple transformer construction can be improved by
bringing the two windings within close contact with each other thereby
improving the magnetic coupling. Increasing and concentrating the
magnetic circuit around the coils may improve the magnetic coupling
between the two windings, but it also has the effect of increasing the
magnetic losses of the transformer core.
As well as providing a low reluctance path for the magnetic field, the core is
designed to prevent circulating electric currents within the iron core itself.
Circulating currents, called "eddy currents", cause heating and energy
losses within the core decreasing the transformers efficiency. These losses
are due mainly to voltages induced in the iron circuit, which is constantly
being subjected to the alternating magnetic fields setup by the external
sinusoidal supply voltage. One way to reduce these unwanted power
losses is to construct the transformer core from thin steel laminations.

13. In all types of transformer construction, the central iron core is constructed
from of a highly permeable material made from thin silicon steel laminations
assembled together to provide the required magnetic path with the
minimum of losses. The resistivity of the steel sheet itself is high reducing
the eddy current losses by making the laminations very thin. These steel
laminations vary in thicknesses from between 0.25mm to 0.5mm and as
steel is a conductor, the laminations are electrically insulated from each
other by a very thin coating of insulating varnish or by the use of an oxide
layer on the surface.
Voltage Regulation:-
A voltage regulator is used to produce a constant linear output voltage.
It’s generally used with AC to DC power supply. And also it can be used as
well as a DC to DC voltage converter. To regulating low voltage, most used
device is one single IC. 7805, 7812, 7905 etc. 78xx series are design for
positive and 79xx series are for Negative voltage regulator. 7805 is a three
terminal +5v voltage regulator IC from 78XX chips family. See 7805 pin
out below. LM78XX series are from National Semiconductor. They are
linear positive voltage regulator IC; used to produce a fixed linear stable
output voltage. National Semiconductor has also negative voltage
regulator chips family, they indicate with LM 79XX. 78xx is used more than
79xx because negative voltage has a few usability purposes as we see.
I was previously posted a 5v regulated power supply circuit using 7805 IC,
that circuit and this 7805 voltage regulator circuit is almost the same.

14. Circuit diagram of 7805 Voltage Regulator
Fig: 7805 Voltage Regulator Circuit

15. Fig: Pin out of 7805
Its output voltage is +5V DC that we need. You can supply any voltage in
input; the output voltage will be always regulated +5V. But my
recommendation is, don’t supply more than 18V or less than 8V in input.
There used two capacitors in this voltage regulator circuit, they aren’t
mandatory to use. But it will be best if you use them. They helped to
produce a smooth regulated voltage at output. Use electrolyte capacitor
instead of ceramic capacitor.
One limitation of 7805 I have found that is its output current 1A maximum.
Otherwise it is a good voltage regulator if you are happy with 1A. But if
you need over 400mA current in output then you should use a Heat
Sink with IC LM7805. Otherwise it may fall damage for overheating.

16. How ordinary charger work
Most of the small electronic appliances we use in our homes work on relatively
low voltages
Typically 5-10 percent as much voltage as hefty electric appliances like vacuum
cleaners and clothes washers.That means we generally need to use transformersto
"step down" the domestic voltage so it will safely power electronic gadgets without
blowing them up. All those chargers you have (little boxes attached to wires that
plug into things like yourMP3playerandcellphone) actually have electricity
transformers hiding inside. It's easy to understand how these simple chargers work:
electricity flows into the charger from the electricity outlet on your wall. Inside the
charger, a transformer "steps down" the electricity to a much lower voltage. The
low-voltage current then flows from the charger into the battery in your appliance.
The important thing to note is that all three parts of the transformer (the primary
coil, the secondary coil, and the iron core linking them together) are contained
inside the charger:

17. Photo: Ordinary electric charging: all the components of the transformer are
contained inside the charger
HOW INDUCTION CHARGERS WORK
SO FAR SO GOOD— BUT WHAT HAPPENS WITH SOMETHING LIKE AN ELECTRIC
TOOTHBRUSH, WHICH HAS NO POWER LEAD TO PLUG INTO THE WALL? WHEN
YOU STAND THE TOOTH BRUSH ON ITS CHARGER, HOW DOES THE ELECTRICITY
FLOW FROM ITS PLASTIC-COATED BASE INTO THE BATTERY INSIDE THE BRUSH
WHEN PLASTIC IS AN INSULATOR (THAT IS, DOESN'T ALLOW ELECTRICITY TO
FLOW THROUGH IT)?
IT'S NOT MAGIC WE HAVE HERE— IT'S JUST ANOTHER KIND OF TRANSFORMER
IN A CUNNING DISGUISE. AN ELECTRIC TOOTHBRUSH AND ITS CHARGER USE A
TRANSFORMER JUST LIKE A CELL PHONE OR AN MP3 PLAYER, BUT IT'S
CLEVERLY SPLIT INTO TWO PIECES, WITH HALF THE TRANSFORMER IN THE
BOTTOM OF THE TOOTHBRUSH AND THE REST OF IT IN THE CHARGER BASE IT
STANDS ON:

18. ARTWORK: INDUCTION CHARGING: HALF THE TRANSFORMER IS IN THE TOOTHBRUSH;
HALF IS IN THE STAND.
THE PRIMARY COIL IS IN THE CHARGER BASE AND IT HAS AN IRON PEG ON TOP
of it covered in plastic. The secondary coil is in the base of the toothbrush, which
you stand on the iron peg. What's the peg for? It's not just to stop the toothbrush
wobbling about: it's the core that links the primary and secondary coils together
electromagnetically. When the toothbrush is standing on the peg, you've got a
complete transformer that works by electromagnetic induction :energy flows from
the coil in the base to the coil in the toothbrush via the iron peg that links them.
The two ends of the coil in the toothbrush are simply hooked up to the
rechargeable battery inside.

19. USES AREA OF INDUCTIVE CHARGING
Electric car

20. Electric vehicle energy storage systems are normally recharged using direct contact
conductors between an alternating current (AC) source such as is found in most
homes in the form or electrical outlets; nominally 120 or 240 VAC. A well known
example of a direct contact conductor is a two or three pronged plug normally
found with any electrical device. Manually plugging a two or three pronged plug
from a charging device to the electric automobile requires that conductors carrying
potentially lethal voltages be handled. In addition, the conductors may be exposed,
tampered with, or damaged, or otherwise present hazards to the operator or other
naïve subjects in the vicinity of the charging vehicle. Although most household
current is about 120 VAC single phase, in order to recharge electric vehicle
batteries in a reasonable amount of time (two-four hours), it is anticipated that a
connection to a 240 VAC source would be required because of the size and
capacity of such batteries. Household current from a 240 VAC source is used in
most electric clothes dryers and clothes washing machines. The owner/user of the
electric vehicle would then be required to manually interact with the higher voltage
three pronged plug and connect it at the beginning of the charging cycle, and
disconnect it at the end of the charging cycle. The connection and disconnection of
three pronged plugs carrying 240 VAC presents an inconvenient and potentially
hazardous method of vehicle interface, particularly in inclement weather.
In order to alleviate the problem of using two or three pronged conductors,
inductive charging systems have been developed in order to transfer power to the
electric vehicle. Inductive charging, as is known to those of skill in the art, utilizes
a transformer having primary and secondary windings to charge the battery of the
vehicle. The primary winding is mounted in a stationary charging unit where the
vehicle is stored and the secondary winding is mounted on the vehicle
There is a time varying aspect to the AC voltage, and hence there is a time-varying
aspect to the magnetic fields in both the primary and secondary transformer cores.
Typically, house current in the U.S. operates at about 60 hertz (Hz), or cycles per
second. The problem with using a voltage that oscillates at 60 Hz, is that the size of
the components in an inductive charging system is inversely proportional to the
frequency, and thus the lower the frequency of the voltage, the greater the size of
the inductive charging system. Size is extremely critical to vehicle manufacturers
because it is very important to automotive owners. The size and weight of an

21. object directly affects the fuel mileage of the vehicle. Thus in other inductive
charging systems, high frequency voltages, normally above 10 kHz, have been
used to transfer power by radiation and tuned coils.
The present invention relates to inductive proximity charging. More particularly,
the invention relates to a system and method for increasing the efficiency of a
gapped transformer used in inductive charging of a vehicle and for regulating the
load voltage of the transformer.
Working
Referring first to FIG. 1, the inductive charging system according to the invention
will be described. The system includes a charging station 2 and transformer 4. The
transformer includes a stationary primary coil 6 which is preferably mounted on
the ground such as the floor of a garage. The primary coil is connected with the
charging station. The transformer further includes a secondary coil 8 which is
mounted on a vehicle 10. The secondary coil is mounted at a location on the
vehicle so that the vehicle can be positioned adjacent to the charging station with
the secondary coil above the primary coil as shown. Preferably, the coils are
arranged with their axes in alignment for maximum energy transfer. However,
because axial alignment is imprecise, the inductive charging system according to

22. the invention is designed to adjust the charging station to maximize energy
transfer.
The inductive charging system according to the invention will be described in
greater detail with reference to FIG. 2. The charging station 2 is connected with a
power source 12. The power source is preferably a 220 volt AC supply operating at
between 50 and 60 Hz. The charging station includes a power converter 14 which
is capable of converting the incoming source voltage from the power supply into a
voltage of arbitrary frequency and voltage. The voltage is supplied to the stationary
primary coil 6. Current within the primary coil generates a magnetic field 16 which
induces a current in the secondary coil 8 mounted on the vehicle. This in turn
produces an output voltage which is delivered to a battery charger 18 in the vehicle
to charge the vehicle battery.
An AC capacitor 20 is connected in series with the secondary coil 8 to create a
resonant circuit in order to efficiently transfer energy within the transformer and to
regulate the load voltage. The resonant circuit is between the transformer leakage
inductance and the capacitor. Such a circuit is useful when the transformer leakage
inductance is large, as is the case for the coil arrangement according to the
invention, and must be cancelled by the capacitor in order to prevent an
unacceptable voltage drop when the battery charger load is applied.
The primary coil is preferably energized at a frequency corresponding to the
resonant frequency of the primary-to-secondary coil leakage inductance and the
series connected capacitor. In this case, the no load voltage at the output of the
transformer will equal the input voltage multiplied by the secondary-primary turns
ratio and by the coupling factor between the coils. As the secondary coil is loaded,
the voltage drop at the load will be only that due to the primary and secondary
winding resistance, assuming that the primary coil is excited with a constant
voltage. However, there are many factors which alter this ideal scenario.
The coupling factor between the primary and secondary coils, which dictates the
output voltage of the transformer, depends on the relative alignment between the
coils with respect to both the axial and radial positions of the coils. If the primary
coil is energized at 220V AC for example, the secondary voltage at no load may be
220V AC at a gape of three inches and perfect radial alignment. However, if the

23. radial alignment is off by one-third of the diameter of the coils, the secondary
voltage will be significantly lower. The secondary voltage might be below the
acceptable range for the load or might result in excessive secondary coil current,
thereby reducing the efficiency of the inductive charging system. It is therefore
desirable to maintain a regulated voltage at the load for reasonable radial and axial
misalignments of the coils.
According to the invention, reductions in the secondary voltage may be
compensated by adjusting the power input. Accordingly, a voltage sensor 22 is
connected with the output of the secondary coil 8 and the capacitor 20. The voltage
sensor 22 generates a secondary voltage signal. A radio frequency (RF)
communication device 24 is connected with the voltage sensor 22 and delivers the
secondary voltage signal to a controller 26 within the charging station 2 via a
feedback loop. The controller continuously adjusts the voltage applied to the
primary coil in accordance with the secondary voltage so that the secondary
voltage is maintained at a fixed value. Thus, the output voltage is maintained at an
acceptable level regardless of misalignment of the coils or various in the gap
between the coils. The controller also compensates for the resistive voltage drop as
the battery charger load is applied to the inductive charging system. A voltage
sensor 28 connected with the output of the power converter 14 delivers a signal
corresponding to the voltage output of the power converter to the controller for
further adjustment of the power converter to maintain an adequate voltage supply
to the system transformer.
In addition to the normal variations in coupling factors that must be
accommodated, the inductive charging system must be able to accommodate
variation in both leakage reactance and series capacitance, which define the
resonant frequency of the system. Variations in leakage reactance will arise due to
differences in coil geometries and due to steel or conductive material which is
introduced into the magnetic path as a result of application of the coil to the
vehicle. Variations in capacitance also occur over time as the capacitor ages.
In order to adjust for these variations in system resonant frequency, an algorithm is
used in the controller to adjust the frequency of the voltage applied to the primary
coil. At the resonant frequency of the system, the ratio between the output voltage

24. and input voltage will be at a maximum for a given current level. The control
system can maintain the excitation voltage frequency at the resonant frequency by
periodically applying slight variations to the excitation frequency and then
measuring the output to input voltage ratio. By comparing the ratio before the
adjusted frequency with the ratio at the new frequency, an appropriate adjustment
can be made to the excitation voltage frequency. Because the resonant frequency
will not, in any practical application, vary by more than approximately 10-20%
from a nominal value, the adjustments to the excitation voltage frequency would
need to be relatively minor and performed relatively infrequently in order to
maintain the optimal value. It will be apparent to those of ordinary skill in the art
that there are a number of algorithms which may be utilized to implement this
iterative technique for maintaining the system resonance.
This corresponds to approximately 8A for a 3.3 kW 400VDC charger and
approximately 16A for a 6.6 kW 400VDC charger.
Power Mat 3X
Power Mat 3X as shown in Figure 5 is a sleek, slim three position Wireless
charging mat for home and office. A magnetic attraction between every receiver
and each access point on every Mat assures that alignment is precise and the most
efficient charging occurs. Communication between the Mat and the Receiver
allows the mat to deliver an exact amount of power for the proper length of time so
that the transfer of power is safe and efficient and no energy is wasted. When the
device reaches full charge, power is shut off to that device, which avoids
overcharging of the device's battery as well as saves energy. Once full power is
achieved and
the Auto Shut Off has occurred to save energy, the system will
monitor the status of the battery in the device. If the battery is

25. used, the system will again initiate charging and return the battery to a full charge.
Artificial heart (transcutneous energy transfer):
With the number of cardiac patients increasing dramatically each year, the
potential for development of implantable circulatory assist devices is remarkable.
Such circulatory assist devices consist of totally artificial hearts and ventricular
assist devices. These devices usually require 12-35 W for operation, and they are
powered by portable battery packs and dc-dc converters. Recently, however, there
has been great interest and subsequent development of transcutaneous transfer of
electrical energy to these circulatory assist devices. A depiction of how such a
system is implanted as represented by the Abiocor artificial heart system is shown
below.

26. Figure 1. Transcutaneous energy transmission system location of implantation
Development of such circuitry involves inductive coupling. Inductive coupling
allows for the transfer of energy without any electrical contact. This technique is
accomplished by a power supply that employs a transcutaneous transformer. The
primary of the transformer is to be placed externally with respect to the body. The
secondary winding of the transformer lies underneath the skin. The spacing of
approximately one to two centimeters between the primary and the secondary of
the transformer contributes to the extremely large leakage inductance. This leakage
inductance is much higher than the magnetizing inductance and as a result, the
voltage gain is low. Consequently, a high percentage of primary winding current
flows through the magnetizing inductance in order to reduce the voltage gain. Use
of a dc-dc converter employing the resonance of the secondary side lowers the
impedance and improves the voltage gain. Below is the equivalent circuit model
for the transcutaneous energy transmission circuit.

27. Figure 2. Equivalent circuit model for transcutaneous energy transmission circuit
The circuit in Figure 2 is currently being implemented in FEMLAB. FEMLAB
offers the opportunity to model the above circuit by employing the finite element
method to solve partial differential equations used in electromagnetics and more
specifically in the above circuitry. In the future, this FEMLAB model will be
implemented in the VTB platform. The uses of such modeling are quite expansive.
The concept of transferring electrical energy wirelessly can be applied in medical
fields as well as in areas in which the transfer of energy is compromised by
environmental conditions. Such a case exists in transferring energy to electric ships
surrounded by water. Hence, contactless energy transfer has many applications and
the future has much potential in this area.
Toothbrushes
Specification
1. Rotates clockwise and counterclockwise 8000rpm.
2. Lasts up to14 days when brushing two mins, twice a day
3. Brush your teeth for about 2mins, move the brush head between the teeth,
brushing the outside first, then the inner side and finally the chewing surface.
4. Wash the toothbrush with water and dry it
5. For optimal result and better tooth and mouth hygiene, replace the brush head
every month
6. Overall size: Height: 25mm Length: 220mm (assembled)
7. Weight: 202g

28. Mobile Charger:
According to Apple's most recent patent application, "Wireless power utilization in
a local computing environment," you could soon be charging your iOS device
simply by keeping it close to your computer system. In case this sounds too
pedestrian for you, the research comes from the field of midrange wireless power
transfer physics. Near field magnetic resonance is used to power devices within

29. 1meter of the power base. Without a mat or extra case.
Inductive Mobile charger

30. Advantage
Inductive charging carries a far lower risk of electrical shock, whencompared with
conductive charging, because there are no exposed conductors .The ability to fully
enclose the charging connection also makes the approach attractive where water
impermeability is required; for instance, inductive charging is used for implanted
medical devices that require periodic or even constant external power, and for
electric hygiene devices, such as toothbrushes and shavers, that are frequently used
near or even in water. Inductive charging makes charging mobile devices and
electric vehicles more convenient; rather than having to connect a power cable, the
unit can be placed on or close to a charge plate .For example, toothbrushes are
guaranteed to get wet during operation. So obviously it would be quite dangerous
to have a wired object that operates in a watery environment. Of course, they could
use some system where the cord could be disconnected during operation, but then
that would become tedious for users. In this case, inductive charging fits perfectly;
there's no fiddling with a wire and more importantly, water won't pose a safety
hazard. As for using it for speakers, it depends on a lot of things. Mainly I would
say it depends on the number of speakers actually, since having lots of separate
charging stations might be more cumbersome than using a single inductive station.
Again though, you'd have to look at the efficiency, and also whether it might be
possible to use a very simple (inexpensive) multi-docking station using conductive
chargers instead.

31. Disadvantage
The main disadvantages of inductive charging are its lower efficiency and
increased resistive heating in comparison to direct contact. Implementations using
lower frequencies or older drive technologies charge more slowly and generate
heat within most portable electronics. Inductive charging also requires drive
electronics and coils, increasing the complexity and cost of manufacturing .Newer
approaches reduce transfer losses through the use of ultra-thin coils, higher
frequencies, and optimized drive electronics. This result in more efficient and
compact chargers and receivers, facilitating their integration into mobile devices or
batteries with minimal changes required. These technologies provide charging
times comparable to wired approaches, and they are rapidly finding their way into
mobile devices. For example, the Magne Charge system employed high-frequency
induction to deliver high power at an efficiency of 86% (6.6 kW power delivery
from a 7.68 kW power draw).A toothbrush which takes about 16 hours to charge,
only lasts about 15minutes. Of course, the main reason for the inefficiency is that
the design forces the use of an inefficient 'transformer' type of circuit (since you
can't use a solid iron core to link the two circuits).The other problem is that you
still need to supply power to the base station. And so you never fully escape the
need for a conventional conductive charger in the end.
Reference:
1. http://answers.yahoo.com/question/index?qid=20081222154050AAANpjF

32. 2. http://web.mit.edu/newsoffice/2007/wireless-0607.html
3. http://en.wikipedia.org/wiki/Inductive_charging
4. http://lifehacker.com/5598744/hack-an-induction-charger-to-work-with-any-
cellphone
5. http://www.explainthatstuff.com/inductionchargers.html
6. http://www.instructables.com/answers/How-do-I-build-an-inductive-charger/
7. http://en.wikipedia.org/wiki/Electric_car
8. http://en.wikipedia.org/wiki/Artificial_heart
9. http://en.wikipedia.org/wiki/Magne_Charge
10. http://en.wikipedia.org/wiki/WiTricity
11. http://en.wikipedia.org/wiki/Electromotive_force
12. http://en.wikipedia.org/wiki/Electromagnetic_induction
13. http://en.wikipedia.org/wiki/Rectifier