CHAPTER IV DESIGN OF TESLA COIL

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1 CHAPTER IV DESIGN OF TESLA COIL In this chapter, the design and calculation regarding spark gap tesla coil is shown as well as the design for the voltage regulator and the zero voltage switching driver with schematics and discussions. Voltage Regulator Figure 4.1 Regulated Power Supply 24V, 10A Schematic Diagram The diagram above shows the power supply with MSK5012 voltage regulator, an output of 24V, 10A that will be supplying the zero voltage switching flyback driver. The MSK5012 linear regulator has a variable voltage output that depends resistors R1 and R2 as shown in Figure 4.2. Furthermore, the capacitors Cin and Cout act as filters to provide a smooth flow of current and voltage towards the driver. Figure 4.2 Proper Resistor Divider Connection Retrieved from M.S.KENNEDY CORP (2006)

Zero Voltage Switching Flyback Driver Figure 4.3 The proponents Zero Voltage Switching Flyback Driver The driver stage is the driver for Flyback transformer.

2 Zero Voltage Switching Flyback Driver Figure 4.3 The proponents Zero Voltage Switching Flyback Driver The driver stage is the driver for Flyback transformer. Researchers will be using the Zero Voltage Switching (ZVS) Driver because it is the most conventional way of converting DC to a square wave during the switch s on-time with resonant switching transitions (Andreycak,1999). Furthermore, the regulation of the flyback transformer is accompanied by adjusting the duty cycle to reduce further hysteresis in the transformer due to HV output. When the ZVS is switched off the LC tank circuit resonates. Zero Voltage Switching Driver also reduces FMI/EMI transitions, reduces gate drive requirements i.e. Miller effect.

3 Fig 4.4 Zero Voltage Switching Driver Schematic Diagram by Mazilli Tesla Coil In this section the calculations with regards to the primary coil, tank capacitor, secondary coil, and toroid will be shown. The resonant frequency, the length and the wire diameter, etc. Primary Coil The primary coil is made up of AWG No. 7 Copper Conductor. The primary coil is set into a flat coil because this type of design is more efficient when it comes to high-power tesla coils according to Jadwani et. al The normal spacing for the turns in the primary coil is 0.25 thus setting its value to that. American Wire Gauge No. 7 has a diameter of 0.144, and setting the turns into 15, the total diameter, average radius, and the width of the coil can now be calculated. Moreover, the primary coil has an inner diameter of six (6) inches.

4 Fig 4.5 Primary coil with 15 turns. Using the formula below, the total diameter of the coil can be calculated: Outer Diameter = Inner Diameter + (2(No. of Turns)(Wire Diameter + Spacing)) Outer Diameter = 6 + (2(15)( )) Outer Diameter = 17.82" To solve for the width W: To solve for the average radius R: To solve for the length of wire: Width W = No. of Turns(Wire Dia. +Spacing) W = 15( ) W = 5.91" Radius R = (Inner Diamter + Width)/2 R = ( )/2 R = 5.955" Outer Dia. +Inner Dia. Wire Lenght = No. of Turns pi ( ) 2 Wire Length = 15π( ) 2 Wire Length = " Wire Length = meters

Thus, the inductance of the coil is: L p = (NR)2 8R + 11W (15 5.955) 2 L p = 8(5.955) + 11(5.91) L p = 70. 89884 μh Secondary Coil The secondary coil is made up of magnetic wire, and PVC pipe.

5 Thus, the inductance of the coil is: L p = (NR)2 8R + 11W ( ) 2 L p = 8(5.955) + 11(5.91) L p = μh Secondary Coil The secondary coil is made up of magnetic wire, and PVC pipe. The secondary coil is a 26 AWG magnetic wire that has inch cross-sectional diameter. The secondary coil is set into 20 in. high and 4 in. diameter, therefore, dividing the height into the crosssectional diameter creates the number of turns require. Thus, the number of turns is equal to Furthermore, the secondary coil has resistance, self-capacitance, and inductance. Fig 4.6 Varnish-applied secondary coil with 1177 turns To Solve for Self-Capacitance: Based on R. Connick (2011) Csc 1 = KD Heigh of Coil (in. ) K = Diameter of Coil (in. )

6 K = ( 20 4 ) K = Csc 1 = ( )(Diameter of Coil in cm. ) Csc 1 = ( )(10.16) Csc 1 = pf Based on M. Behrend (n.d.), Csc 2 = 0.29(Height of Coil in inches) (Radius of coil in inches) Radius3 Heigh of Coil Csc 2 = 0.29(20) (2) Csc 2 = pf Averaging Csc1 and Csc2, Csc = Csc 1 + Csc 2 2 Csc = pf To Solve for the Inductance: L s = (Number of Turns X Radius in inches) 2 9(Radius in inches) + 10(Height of Coil in inches) L s = ((1177)(2))2 9(2) + 10(20) L s = μh Solving for the Resistance in the wire: Wire Length = π(1177) Wire Length = m R = ρl A R = ( Ω m)(375.68m) ( π 4 )( )2 R = Ω

Top Load (Toroid) The top load acts as a capacitor in the secondary side of the Tesla coil. The common form of top load is toroid due to its capability to adjust long stacks of high voltages.

7 Top Load (Toroid) The top load acts as a capacitor in the secondary side of the Tesla coil. The common form of top load is toroid due to its capability to adjust long stacks of high voltages. The top load is usually made of aluminum to minimize corona effect. The top load has a total diameter of 16 inches, and a cross-sectional diameter of 4 inches. In this study, the researchers used aluminum ducting that is commonly used in aircon ducting. The researchers used aluminum ducting due to market availability, and to minimize the cost. Solving for Toroid Capacitance: Based on R. Connick (2011), Fig 4.7 Aluminum Toroid C T1 = 1.8(Total Diameter Cross Sectional Diameter) 8(Outer Diameter Cross Sectional Diameter) ln ( ) Cross Sectional Diameter 1.8( ) C T1 = 8( ) ln ( ) C T1 = pf Based on M. Behrend (n.d.),, units in centimeter C T2 = 1.4( Cross Sectional Dia. ) π(cross Sectional Dia. )(Total Dia. CS Dia. ) Total Dia. C T2 = 1.4( ) π(4)(16 4) 16 C T2 = pf

Averaging the values of CT1 and CT2, Tank Capacitor C T = C T1 + C T2 2 C T = 17.

8 Averaging the values of CT1 and CT2, Tank Capacitor C T = C T1 + C T2 2 C T = pf The common capacitor that is used in Tesla coils are polypropylene capacitors due to its linear and negative temperature coefficient of -150ppm. The polypropylene capacitor has a dielectric absorption of 0.02% and a high temperature range which is up to 105 C (H.R. Bissell, 1999). However, due to unavailability of polypropylene capacitors in General Santos City the researchers will make their own version of high voltage capacitor out of bottles. There will be eight (8) 1.5L bottles that will have a supersaturated solution of salt and water which will fill more than half of the bottle. For the remaining space, a motor oil will top off the bottle which will float above the salt solution. Fig 4.8. Bottle capacitors set-up. (Retrieved from Jadwani et. al., 2013)

9 Output Voltage The output voltage is the voltage in the secondary side of the tesla coil. With resonance at the primary and secondary coil the formula for output voltage is, V out = V flyback L s L p Since the flyback transformers do not give exact output voltage, however the output voltage ranges from 50kV to 80kV. For safety purposes and for the sake of calculations, the researchers will be using 80kV as an output voltage of flyback transformer. Thus, the output voltage is V out = MV

Spark-Gap Tesla Transformer

Spark-Gap Tesla Transformer 1 Introduction I built two secondary coils: Small coil D25.4/H119 (Diameter=25.4mm and Height=119mm) and Medium coil D73/H228. I experimented with the spark gap, and observed