Group Leader:
Gonzales, Kervin Tommy A
Members:
Ramos, Justin Rabaya, Janray Leslie, Jaime Manay, Janray
Proposed Topic: Tesla Coil
Additional Features:
Wireless electricity lighting up the bulb without physical contact with electricity
Electromagnetics Relationship:
Magnetic Fields Current Magnetic Induction Transformer Half-Bridge Resonant Circuit
Background:
Brief introduction about Tesla Coil:
A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla around 1891. It is used to produce high-voltage, low-current, high frequency, alternating-current electricity. Tesla experimented with a number of different configurations consisting of two, or sometimes three, coupled resonant electric circuits. Tesla developed the coil in 1891, before conventional iron-core transformers were used to power things like lighting systems and telephone circuits. These conventional transformers can't withstand the high frequency and high voltage that the looser coils in Tesla's invention can tolerate. The concept behind the coil is actually fairly simple and makes use of electromagnetic force and resonance. Employing copper wire and glass bottles, an amateur electrician can build a Tesla coil that can produce a quarter of a million volts.
Setting up the tesla coil: A Tesla coil is consists of two parts a primary and secondary coil, each with its own capacitor. The two coils and capacitors are connected by a spark gap, a gap of air between two electrodes that generates the spark of electricity. The Tesla coil is two open electric circuits connected to a spark gap. A tesla coil needs a high-voltage power source. A regular power source fed through a transformer can produce a current with the necessary power.
How it works: The power source is hooked up to the primary coil. The primary coil's capacitor acts like a sponge and soaks up the charge. The primary coil itself must be able to withstand the massive charge and huge surges of current, so the coil is usually made out of copper, a good conductor of electricity. Eventually, the capacitor builds up so much charge that it breaks down the air resistance in the spark gap. Then, similar to squeezing o ut a soaked sponge, the current flows out of the capacitor down the p rimary coil and creates a magnetic field. The massive amount of energy makes the magnetic field collapse quickly, and generates an electric current in the secondary coil. The voltag e zipping through the air between the two coils creates sparks in the spark gap. The energy sloshes back and forth between the two coils several hundred times per second, and builds up in the secondary coil and capacitor. Eventually, the charge in the secondary capacitor gets so high that it breaks free in a spectacular .The resulting high-frequenc y voltage can illuminate fluorescent bulbs several feet away with no electrical wire connection. In a perfectly designed Tesla coil, when the secondary coil reaches its max imum charge, the whole process should start over again and the device should become self-sustaining. In practice, however, this does not happen. The heated air in the spark gap pulls some of the electricity away from the secondary coil and back into the gap, so eventually the Tesla coil will run out of energy. This is why the coil must be hooked up to an outside power supply. The principle behind the Tesla coil is to achieve a phenomenon called resonance. This happens when the primary coil shoots the current into the secondary coil at just the right time to maximize the energy transferred into the secondary coil. Think of it as timing when to push someone on a swing in order to make it go as high as possible. Setting up a Tesla coil with an adjustable rotary spark gap gives the op erator more control over the voltage of the current it produces. This is how coils can create crazy lightning displays and can even be set up to play music timed to bursts of current. While the Tesla coil does not have much practical application anymore, Tesla’s invention completely revolutionized the way electricity was understood and used. Radios and televisions still use variations of the Tesla coil today.
Concepts:
Current, Magnetic Field and Induction
The basics of electromagnetism are Current, Magnetic Field and Induction. In Maxwell’s equation which is Ampere’s law stated that current flowing through a wire creates a magnetic field around it.
Transformer
We can coil the wire to use this magnetic field to our advantage. Magnetic fields form the individual turns add together in the center.
Constant current makes a static magnetic field but when we apply changing current through the wire, this tells us that the magnetic field changing in time induces a voltage across the wire proportional to the rate of change of the magnetic field which is called Faraday’s law of induction.
A transformer takes advantage of the law of indu ction to step AC voltages up or down. It consists of two coils of wire around a core. The core is soft iron or ferrite, materials which are easily magnetized and demagnetized.
An oscillating current in the primary winding establishes an oscillating magnetic field in the core. The core concentrates the field, ensuring that most of it passes through the secondary. As the magnetic field oscillates, it induces an oscillating current in the secondary coil. The voltage across each turn of wire is the same, so the total voltage across the coils is proportional to the number of turns:
Because energy is conserved, the the higher voltage is smaller by the same
current on the side of the transformer with proportion.
Resonant Circuit
A resonant circuit is like a tuning fork: it has a very strong amplitude response at one particular frequency, called the resonant or natural frequency. In the case of the tuning fork, the tines vibrate strongly when excited at a frequency determined by its dimensions and the material properties. A resonant circuit achieves the highest voltages when driven at its natural frequency, which is determined by the value of its components. Resonant circuits use capacitors and inductors, and therefore are also kn own as LC circuits. They are also known as “tank circuits,” because of the energy storage elements present. Capacitors store energy in the form of an electric field between two plates separated by an insulator, known as a dielectric. The size of the capacitor is dependent upon the size of the plates, the distance between them, and the properties of the dielectric. Inductors store energy in the form of a magnetic field around a wire, or in the middle of a loop of wire.
The resonant frequency of an LC circuit, or the frequency at which the energy cycles between the capacitor and inductor as described above, is:
Materials:
Spark Gap Spark gap is used as a switch to momentarily connect the primary capacitor to the primary coil. When the gap is shorted the cap is allowed to discharge into the coil.
Primary Coil Primary coil is used with the primary capacitor to create the primary LC tank circuit. The Primary coil also couples to the secondary coil to transfer power from the primary to the secondary circuit.
Secondary Coil Secondary coil and the top load create the secondary LC tank circuit. The secondary coil also couples to the primary coil and transfers power from the primary circuit to the secondary circuit.
Top Load Top load acts as a capacitor in the secondary circuit
Calculations:
Tr ansfor mer I nput and Output
EPIP = ESIS EP = primary voltage IP = primary current in amps ES = secondary voltage IS = secondary current in amps
Resonant Circui t F ormula
F = frequency in hertz L = inductance in henrys C = capacitance in farads
Spiral Coil I nductance
L = inductance of coil in microhenrys (µH) R = average radius of the coil in inches N = number of turns W = width of the coil in inches
H eli cal Coil I nductance
L = inductance of coil in microhenrys (µH) N = number of turns R = radius of coil in inches (Measure from the center of the coil to the middle of the wire.) H = height of coil in inches
Secondary Coil Di mension s
T = AH
L = length of wire in feet D = outer diameter of coil form in inches H = height of windings in inches A = number of turns per inch T = total number of turns B = thickness of wire in inches
En ergy for L and C
Capacitance
Inductance
J = 0.5 V2 C
J = 0.5 I2 L
J = joules of energy stored V = peak charge voltage I = peak current C = capacitance in farads L = inductance in henries
Peak values of V and I are stated in order to emphasize not to use RMS values. The energy stored at any given time is of course: J(t) = 0.5 [V(t)]2 C and J(t) = 0.5 [I(t)]2 L
References: http://www.livescience.com/46745-how-tesla-coil-works.html http://www.teslasociety.com/teslacoil.htm http://powerbyproxi.com/wireless-power/ https://en.wikipedia.org/wiki/Wireless_power_transfer https://en.wikipedia.org/wiki/Tesla_coil https://www.youtube.com/watch?v=6cbMuVTNsVI Engineering Electromagnetics 8th edition by Hayt http://onetesla.com/tutorials/how-a-tesla-coil-works http://www.teslacoildesign.com/construction.html http://teslacoils4christ.org/TCFormulas/TCFormulas.htm http://www.deepfriedneon.com/tesla_frame6.html
