Final Research Update -
Bimodal Tesla Coil
Collin Matthews
Advisor: Dr. Jovan Jevtic
5/21/2013
Abstract
The Tesla coil, invented in the 1890s, has found applications in areas as varied as radio-technology, medical and industrial X-rays, electromagnetic pulse weapons, lightning simulators, education and entertainment. Since its creation many evolutions have occurred: spark gap, rotary spark gap, vacuum tube, and solid-state designs. When used as lighting simulator Tesla coils are only capable of producing current pulses of short duration as would naturally occur in cold lightning. However, the most damaging form of lighting, hot lightning is a continuous current of much longer duration. We are proposing the first bimodal Tesla coil. In our design we will simultaneously excite the Tesla coil at two frequencies. The purpose of the first frequency is to excite the conventional mode of the Tesla coil, to establish a high voltage that can initiate the breakdown of the spark gap. Unique to our design is the second frequency, which excites a higher order mode of the Tesla coil resulting in a continuous current flow once the high voltage terminal has been grounded though the spark. Our hypothesis is that the addition of a higher order mode will extend the spark duration, allowing us to add a continuous current component to the discharge of a Tesla coil. We have run simulations based on laboratory measurements of a Test coil. The resonant frequency and driving impedances with the discharge terminal open and short circuited to ground were measured and recorded for the first three resonant frequencies. Using the data from the measurements, we built a power supply capable of producing two independently adjustable frequencies to drive the coil.
1 of 20
Table of Contents
Abstract .............................................................................................................................................1
Project Timeline and Updates.............................................................................................................3
Basic principles and operation of a rotary spark gap coil .....................................................................4
Why is a Rotary Interrupter Spark Gap Important?.................................................................................. 4
The Oberbeck Theory .........................................................................................................................5
Initial Multisim Simulation .................................................................................................................6
What I have learned from helical resonator research ..........................................................................9
Helical resonators and a bimodal coil ............................................................................................... 10
Physical Coil Characteristics.............................................................................................................. 11
DC Resistance .......................................................................................................................................... 11
Physical Coil Characteristics .................................................................................................................... 11
Coil Inductance ....................................................................................................................................... 12
Measured Resonant Frequencies ........................................................................................................... 13
Matlab Calculated Resonant Frequencies .............................................................................................. 13
Matlab Projected Voltage and Current Distributions ............................................................................. 14
Bucket Coil Basic Physical and Electrical
