28-08-2014, 12:12 PM
WITRICITY ON SEMINAR REPORT
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Wireless Electricity Transmission
Abstract
The idea of wireless generation and transmission of
power is in experiment from a long time. Here, in this paper
we are trying to develop a proper device that can generate
voltages and then transmit them wirelessly through a local
network (after that our next stage will be to expand it to globalscale) in the RF range for household electricity requirement.
Ongoing engineering revolutions going in field of
transmission and distribution will help us to make this dream
to come in reality. The person who first paved the way of
dreaming wireless power is NIKOLO TESLA. In 1888 he
developed the principles of his Tesla coil and began working
with his ideas for polyphase systems, which would allow
transmission of AC electricity over large distances. The
connection would be made by electrostatic induction or
conduction through plasma. Tesla firmly believed that
Wardenclyffe would permit wireless transmission and
reception across large distances with negligible losses. But
after lighting vacuum tubes wirelessly, he provided us with
enough evidence of the potential and feasibility of wireless
power transmission network
Introduction
Nikolo Tesla generated AC of one million volts
using a conical Tesla coil. Harmlessly passes through human
tissue with virtually no feeling or shocking effects. He was
developing a system for wireless telegraphy, telephony and the
transmission of power, experimented with high-voltage
electricity and the possibility of wireless transmitting and
distributing large amounts of electrical energy over long
distances. Tesla discovered terrestrial stationary waves within
the earth. He demonstrated that the Earth behaves as a smooth
polished conductor and possesses electrical vibrations. he lit
hundreds of lamps wirelessly at a distance of up to twenty-five
miles (40 km). He transmitted signals several kilometers and
lit neon tubes conducting through the ground
What is a Tesla Coil?
A Tesla coil is a category of disruptive discharge
transformer coils, named after the inventor, Nikolo Tesla.
Tesla coils are composed of coupled resonant electric circuits.
It is a special transformer that can take the 110v electricity
from our house and capable of converting it rapidly to a great
deal of high-voltage high–frequency, low amperage power.
The high frequency output of even a small Tesla coil can light
up fluorescent tubes held several feet away without any wire
connections. The high frequency high-voltage energy
produced possesses qualities unlike conventional electricity. It
defies most insulation material , transmits energy without
wires , produces heat , light , and noise yet harmlessly passes
through human tissue with virtually no feeling or shocking
effects. A large number of spent or discarded fluorescent tubes
(their burned out cathodes are irrelevant) will light up if hung
near a long wire running from a Tesla coil while using less
than 100 watts drawn by the coil itself when plugged into an
electrical outlet. Tesla, described new and useful combinations
employed in transformer coils. The transmitting coil or
conductor arranged and excited to cause currents or oscillation
to propagate through conduction through the natural medium
Operational Principle
Later coils consist of a primary tank circuit, which is a series
LC circuit composed of a high voltage capacitor, spark gap,
and primary coil; and the secondary LC circuit, a series
resonant circuit consisting of the secondary coil and the toroid.
Most modern coils use only a single secondary coil. The toroid
actually forms one terminal of a capacitor, the other terminal
being the Earth ("ground"). The primary LC circuit is "tuned"
so that it will resonate at the same frequency as the secondary
LC circuit. The primary and secondary coils are magnetically
coupled, creating a dual-tuned resonant air-core transformer; a
Tesla Coil's windings are "loosely" coupled, with the primary
and secondary typically sharing only 10-20% of their
respective magnetic fields. Tesla Coils spread their electric
field over a large distance to prevent high electrical stresses in
the first place, thereby allowing operation in free air
Some notes on Power Consumption of TeslaCoil
1) Power Supply –
Initially, in circuit the upto±170 V is
applied to the inverter. Then a step-up transformer (240/2400
transformer) is to be used ahead of the inverter. A factor of ten
(10(±170) = ±1700 V) gave us enough range. This is an oil
filledtransformer, called a pole pig and was rated at 5kVA, so
the rated input current is 5000/240 = 20.8 A. This is a very
conservative rating, for continuous operation (run four hours
at 30 A without a problem) in a 40oC ambient
Current Sense Resistors
In the metal case containing the
inverter, there are several other components besides those
shown in Fig. 2. These include the current sense resistors, a
filter for the current waveform to the scope, a small current
transformer for supplying current information to the
controller, and some high frequency capacitors for voltage and
current support. These are shown in Fig. 3. The switches
SW1-SW8 represent the 8 IGBTs in the inverter
Wireless energy transfer
It is the transfer of electromagnetic energy from power to do
work via conduction, induction, or transmission without a
physical connection. Wireless energy transfer, does not require
a physical medium through which to flow. With the basic
principle thus established, the challenge then is to channel the
energy of transmission to ensure efficient reception,
whereupon it can be converted into useful power, a flashlight
beam focused narrowly (by a lens) onto a solar cell will
minimize the amount of energy which does not fall on the
receiver and is ambiently lost. The advent of technology for
much higher transmission frequencies, like those used by
microwave transmitters, created the possibility of relaying
electromagnetic energy through the application of directional
antennas. Lasers, which create a coherent and tightly confined
beam of light energy, are even more appropriate. Wireless
Transmission
The Tesla Coil primary winding, spark gap, and tank capacitor
are all connected in series. Once the gap fires, the electrical
behavior of either circuit is identical. In the typical circuit the
spark gap's short circuiting action prevents high frequency
oscillations from "backing up" into the supply transformer.
Regardless of which configuration is used, the HV transformer
must be of a type that self-limits its secondary current by
means of internal leakage inductance. A normal (low leakage
inductance) high voltage transformer must use an external
limiter (called a ballast) to limit current. NST's are designed to
have high leakage inductance to limit their short circuit current
to a safe level. A large Tesla coil of more modern design can
operate at very high peak power levels, up to many megawatts
(a million watts). It should therefore be adjusted and operated
carefully, not only for efficiency and economy, but also for
safety. If, due to improper tuning, the maximum voltage point
occurs below the terminal, along the secondary coil, a
discharge (spark), or possibly a ball of plasma, may break out
and severe damage can take place. Also the atmosphere below
5 miles is also viewed as a propagating medium for a portion
of the aboveground circuit, and, being an insulating medium,
electrostatic induction would be involved rather than true
electrical conduction
Reception
The secondary coil and its capacitor can be used in receiver
mode. The parameters of a Tesla Coil transmitter are
identically applicable to it being a receiver due to reciprocity.
Impedance, is not applied in an obvious way; for electrical
impedance, the impedance at the load (e.g., where the power is
consumed) is most critical and, for a Tesla Coil receiver, this
is at the point of utilization (such as at an induction motor)
rather than at the receiving node
The dangers of high frequencyelectrical current are sometimes
perceived as being less than atlower frequencies. Large Tesla
Coils and Magnifiers can deliverdangerous levels of high
frequency current, and they canalso develop significantly highervoltages (often 250,000–500,000 volts, or more). Because of the higher voltages, largesystems can deliver higher energy, potentially lethal, repetitivehigh voltage capacitor discharges from their top terminals
Conclusion
The wireless power generation and distribution concept can
open up a new dimension is the field of science and
technology. With the slowly depletion of natural reserves like
oil, natural gas and coal, the world is nearing a already
situation of steep energy crunch. A fully developed Global
Wireless Energy System would, conceivably, allow for the
removal of many existing high-tension power transmission
lines, and facilitate the interconnection of electrical generation
plants on a global scale. Tesla believed that energy cold be
efficiently transmitted from the facility by true electrical
conduction through the earth, either displacement currents,
i.e., electrostatic induction or, with a high-power system, true
electrical conduction through plasma. Tesla called his wireless
technique the "disturbed charge of ground and air method."
And we trying to put the final shape to his ideas