Projects:2017s1-186 Playing Music Through a Tesla Coil
This project aims to design and test a system comprising of two Tesla Coils and a Control Interface. Each Tesla Coil will utilise a different switching technology which we aim to analyse and compare the performance and characteristics of the differing types. The control panel will be used to send audio information to both coils in a format suitable to each coil type.
Dr Wen Soong 
Dr Andrew Allison 
Basic Theory of Operation
A Tesla Coil is a resonant air core transformer capable of producing very high voltages. While there are many different topologies for Tesla Coils the general principle of operation remains the same for each.
A Tesla Coil is comprised of several elements; a high voltage power supply, a capacitor C1 and primary coil L1 which form a tuned resonant circuit and a switching device SG (traditionally a spark gap). A secondary coil L2 tuned with the primary coil L1 to form an air cored resonant transformer. A capacitive electrode or ‘top-load’ E is used to suppress premature corona discharge (high voltage arcing) which serves to improve the quality factor and increase the output voltage.
In Figure 1, C2 is a representation of the capacitance of the secondary coil windings in parallel with the capacitance of the top-load E. During operation the coil operates a repeating cycle as follows; C1 will charge and then discharge through the spark gap creating a pulse through the primary coil L1 which excites the secondary coil L2 producing high voltages.
Vacuum Tube Tesla Coils (VTTC)
A VTTC operates on the same principle described above however it replaces the spark gap with a switching component called a Vacuum Tube (Valve), which is an older switching device commonly used in the early to mid 1900s before solid state devices such as transistors became popular.
Vacuum tube coils are typically less powerful than a spark gap coil but are more controlled; this is because most tubes cannot handle the current that a spark gap can, however because they are controlled switching devices the drive waveform and frequency can be forced; this is a useful feature when wanting to audio modulate a tesla coil.
Solid State Tesla Coils (SSTC)
Solid state Tesla Coils as the name indicates, use solid state switches (usually IGBTs) as the switching device. A variant of the SSTC is the Dual Resonant SSTC (DRSSTC). It uses a resonant primary circuit tuned to the same frequency as the secondary circuit, as both coils are resonant the quality factor is higher, this means higher voltages are achievable for the same power input.
Some of the limitations of using solid state switches include, operating frequency and primary circuit voltage. The maximum switching capabilities of most power transistors tend to be around 300kHz however with the rapid advancements in semiconductor technology this limitation may disappear in the near future. The voltage limitation is avoided by designing the primary system to be a high current system (instead of a high voltage system) with very few turns on the primary coil.
1 M Barncob. (2017, May) Kaizer Power Electronics.
2 B Wang, M Dupont, and A Spencer. (2014, August) oneTesla.
3 Dan. (2002, May) VTTC I. - Big vacuum tube tesla coil with GU-81M.
4 unknown. (2013, January) History Website - Valve Reciever Circuitry.
5 M Barncob. (2011, August) Kaizer DRSSTC II.
6 Alex Yuan. (2014, July) Pennsylvania State University Personal Wiki.
7 brtaman. (2010, mar) 4HV.ORG.
9 Steve Ward. (2008, November) DRSSTC-5.
10 P Wokoun. (2003, September) INVESTIGATIONS ON USING A SALVAGED MICROWAVE OVEN TRANSFORMER.
11 Deepdriedneon.com. (2002, March) Deep Fried Neon - Helical Coil Calcualtor.