Basic question about SSTC tesla coil design
profdc9, Tue Apr 26 2016, 12:50AMWhy in a SSTC tesla coil is the primary coil and capacitor driven in series rather than in parallel? I understand that in a SGTC that the spark gap basically acts as a switch which allows the primary coil and capacitor to resonate as a separate circuit. But with a SSTC, the primary coil and capacitor are actively driven. Wouldn't driving the primary coil and capacitor in parallel resonance increase the current while maintaining a more or less constant voltage given by the power supply voltage, so that the combination appears as a near open circuit, as opposed to driving them in series where the combination is a near short circuit? In either case the current is large in the primary coil, but in the case of parallel resonance the large currents are limited to the resonant part of the circuit.
The context is that I am trying to make a circuit model of a SSTC in Qucs (qucs.sourceforge.net) so I can play with different ways of feedback and triggering.
Thanks,
Dan
Re: Basic question about SSTC tesla coil design
Sulaiman, Tue Apr 26 2016, 05:30AM
how would you drive the parallel resonant circuit ?
at resonance it requires a very high voltagge
but 'not-at-resonance' it looks like a near short-circuit.
Sulaiman, Tue Apr 26 2016, 05:30AM
how would you drive the parallel resonant circuit ?
at resonance it requires a very high voltagge
but 'not-at-resonance' it looks like a near short-circuit.
Re: Basic question about SSTC tesla coil design
profdc9, Tue Apr 26 2016, 11:22AM
Near the resonance frequency, the parallel circuit looks like a high impedance load. It would be possible I think to drive it at resonance, but switching the transistors on the either side of the bridge slightly in advance of the peak voltage on the parallel circuit tank, so that the phase of the excitation would slightly lead the natural resonance phase of the parallel circuit. Because of the difference in potential between the driving circuit and the parallel circuit at the time the voltage is applied, the applied voltage would add to the current in the load constructively, and therefore increase the current on each consecutive cycle. The voltage in the load would remain relatively constant near the voltage of the rails, but the current would be increased. The secondary would act as a damping load on the primary coil, limiting the current in the parallel circuit.
Dan
profdc9, Tue Apr 26 2016, 11:22AM
Near the resonance frequency, the parallel circuit looks like a high impedance load. It would be possible I think to drive it at resonance, but switching the transistors on the either side of the bridge slightly in advance of the peak voltage on the parallel circuit tank, so that the phase of the excitation would slightly lead the natural resonance phase of the parallel circuit. Because of the difference in potential between the driving circuit and the parallel circuit at the time the voltage is applied, the applied voltage would add to the current in the load constructively, and therefore increase the current on each consecutive cycle. The voltage in the load would remain relatively constant near the voltage of the rails, but the current would be increased. The secondary would act as a damping load on the primary coil, limiting the current in the parallel circuit.
Dan
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