Wireless charging using electromagnetic induction, and resonance magnetic coupling. Effects and limitations, cheallenges faced and meathods to overcome. Success Case study. References included.

1. Wireless Charging
of
Electric Vehicles
Presented by:
Kush Kulshrestha
EEE Section-I
UE124027

2. What are EVs ?
An electric vehicle (EV), also referred to as an electric drive vehicle,
uses one or more electric motors or traction motors for propulsion.
An electric vehicle may be powered through a collector system by
electricity from off-vehicle sources, or may be self-contained with a
battery or generator to convert fuel to electricity. EVs include road
and rail vehicles, surface and underwater vessels, electric aircraft
and electric spacecraft. [1]

3. Need for EVs
 Global Warming/Climate Change.
Due to release of carbon dioxide by
burning of fossil fuels.
 Rising Prizes.
Due to depletion of the reserves of
Oil and Natural Gas.
 Acid Rain
Due to Sulphur Dioxode released by
burning of fossil fuels.
 Effect on Human Health.
Air polution from vehicles and coal powered power palnts.
 Impact on Aquitic Life by Oil Spills.

4. Problem with EVs
Battery technology is expensive because batteries in
electric cars need to be able to hold massive
amounts of charge to make the cars practical for
most drivers. So they are made for expensive
materials which are tough to procure. [2]
1
Affordability
Solution
Electric cars could be less expensive if electric car
makers could ramp up production volume and use
economies of scale. This will happen over time.

5. Problem with EVs
People are worried about how far they can travel in
electric cars before their batteries peter out as most
production electric cars about to hit the market can
only go about 100 miles (160.9 kilometres) on a
single charge. [3]
2
Range Anxiety
Solution
Provide access to a specialized charging station
which are currently in short supply.

6. Problem with EVs
While some charging stations are out in trial phases,
most charging still needs to be at home, in a garage.
That means that people who live in shared housing
or use street parking will likely have the hardest time
charging.
3
Charging Stations
Solution
Improving the infra structure and providing more
public charging stations on highways and in cities.

7. Types of Charging
Systems
Conductive Charging
It utilizes connector
between the Electric
power source and
vehicle battery.
This type of charging is
utilized in Residential
areas.
Inductive Charging
Wireless charging
coupled with magnetic
resonance to transfer
power from a
transmitting pad to a
receiving pad
Battery Switching
Depleted EV battery
pack is switched with a
fully charged battery
pack in the switching
station.

8. Wireless Charging or
Inductive Charging
The technology depends on the same principle of electromagnetic induction
that enables a transformer to change the voltage of an alternating current.
This current flows through one coil of wire, creating a magnetic field whose
polarity reverses with each cycle and inducing a corresponding alternating
field in a secondary coil.
Transformers usually include an iron-rich core, which links the coils and
increases the field strength, but you don’t really need it. If the two coils are
separated by air, current flowing through the first coil will still create a
magnetic field, which will still be picked up by the second coil—it just won’t be
picked up as well. The greater the air gap, the less efficient the transfer of
power will be.

9. Wireless Charging or
Inductive Charging

10. Wireless Charging or
Inductive Charging
The Problem
In 1994, the Partners for Advanced Transit and Highways project, led by
researchers at the University of California, Berkeley, demonstrated the
transfer of power from coils buried in the road to the cars above.[4] The
receiving coils were on the underside of the test vehicles and were
separated from the transmitting coils by an air gap of only 7.5 centimeters.
They captured 65 percent of the injected power, but a scheme that wastes
35 percent of the power could not be brought to the market.
How, then, to increase the efficiency of the power transfer without having to
make the low-slung receivers even more vulnerable??

11. Magnetic Resonance
Coupling
When a transmitting coil sends electromagnetic
waves tuned to a frequency matching the
resonance of a circuit holding a receiving coil, it
will transfer energy to it very efficiently.

12. Magnetic Resonance
Coupling
The Solution
In 2007, MIT professors caught the world’s attention by powering a light
bulb suspended in space, 2 meters away from the transmitting coil. Those
researchers went on to found a Massachusetts start-up, WiTricity Corp.,
which is working with several auto companies on wireless charging stations
for household garages. Quebec’s Bombardier is developing its Primove
system in Europe to transmit power to public buses and trams.[5]

13. Magnetically
Coupled Resonance
in EV’s

14. Magnetic Resonance
Coupling
Success Case Study: OLEV Developed by KAIST
On 9 March 2010, researchers from The Korea Advanced Institute of Science and
Technology (KAIST) launched Online Electric Vehicle (OLEV), a public transport system
using a “recharging road“.
Electric power strips have been buried 30 cm (11.8 in) under the road surface and
connected to the national grid. Pick-up equipment underneath the vehicle then
collects power through non-contact magnetic induction which is used either to power
the vehicle prime-mover or for battery charging.
As the tram rolls along, magnetic sensors in the road detect its approach and
activate the transmitters to send 62 kilowatts to the receiving coils on the underside
of the tram. The bus still contains a battery, but it carries 40 percent less energy than
it would have to otherwise. It’s also 6 percent lighter and significantly cheaper.

15. Magnetic Resonance
Coupling
Success Case Study: OLEV Developed by KAIST
Key Advances made by the team:
 Design of the Electromagnetic Field
An engineer can choose the relative strength of the two components fields – electric
and magnetic.
 Increase in efficiency of Power Transmission using shaped Magnetic Field
The path of the magnetic field from the transmitter coil to the receiver coil is guided
by the presence of the ferrite cores on both sides.
As a result, the OLEV bus was charged while it was being driven, its body 20 cm above the
road, and achieved an average transfer efficiency of 75 percent.

16. Magnetic Resonance
Coupling
Further Modifications / Future Scope:
By embedding the transmission coils at points where vehicles stop and linger, like
parking garages, taxi stands, traffic lights, the vehicles can be charged more
efficiently and investments in construction can be reduced. Hence charging at
places where vehicles stand a lot of time standing gives a boost to the efficiency.
By selecting the resonance frequency in kilohertz range, a proportionally higher
voltage is generated in the receiving coils and gain better transfer efficiency. But
increasing the frequency above the megahertz range, the cables for the
transmitting and receiving coils could suffer from Skin Effect, which is very less in
Kilohertz range.[6]

17. Magnetic Resonance
Coupling
Challenges to be solved:
Efficiency
Although Magnetic Resonance Coupling has increased the efficiency of wireless
power transmission to the EVs up to 75 percent, still 25 percent of the energy is
wasted. Improving this efficiency up to 90 percent is very essential if wireless
charging is to be used on a huge scale.
Heat Generated
For High Power transfer system like in railways, the heat generated in the system is
very large and difficult to remove.

18. Magnetic Resonance
Coupling
Challenges to be solved:
Compact Design
How to make the pickup module light and compact enough to use in small air-gap
trains, trams, buses, and cars is the next challenge.
Cost Reduction
In order to make the system of wireless transmission of power to EVs feasible for
large scale use, the developers have to drastically reduce the cost of the system by
finding inexpensive ways to build the components. Currently, construction of
Km loop at the zoo, costs around $550,000.

19. References
◇[1] https://en.wikipedia.org/wiki/Electric_vehicle
◇[2] http://auto.howstuffworks.com/challenges-facing-the-electric-car-industry.htm
◇[3] http://www.cheatsheet.com/automobiles/5-problems-standing-in-the-way-of-
electric-vehicle-adoption.html/?a=viewall
◇[4] http://spectrum.ieee.org/transportation/advanced-cars/the-allelectric-car-you-
never-plug-in
◇[5] http://spectrum.ieee.org/transportation/advanced-cars/the-allelectric-car-you-
never-plug-in
◇[6] http://www.wirelesspowerconsortium.com/technology/magnetic-resonance-and-
magnetic-induction-making-the-right-choice-for-your-application.html

20. Thanks!
Any questions?
Find me at:
kulshresthakush@gmail.com
kushkul.wordpress.com