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Old 7th Nov 2017, 8:22 pm   #104
Al (astral highway)
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Join Date: Nov 2006
Location: London, UK.
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Default Re: Design-and-building a large valve Tesla coil (class C, Armstrong oscillator).

Note:

1) the MOSFET driver chip has two outputs. Together they can source 6A. I note from a quick mental calc that 'only' about 2A is needed to switch this HiperFET on and I'm only using one output. This is a perfect little example of peak (pulse) power versus average power, a nice metaphor for the way the whole Tesla coil will work. The power supply regulator runs cold, and so does the driver chip- peak current is intense, but average current is low.

1b) Also, peak voltage across the MOSFET is when it is switched off. This is again clearly shown by comparing the (x 10 ) blue trace (sinusoidal and square combined) with the yellow Gate pulse. The MOSFET is off for 3/4 of the time.

2) The advantage of having built a robust modulator already is that I can model the characteristics of the main resonators in detail at low voltage. This includes the design of the grid leak. Although I won't know how the power oscillator valve behaves until later, I will be able to experiment with various values of R and C to see the resultant waveform, instead of either guessing or messing around with a high voltage probe uniformed, later on. So that's all good!
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Last edited by Al (astral highway); 7th Nov 2017 at 8:40 pm.
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