Where to find a large power supply or amplifier that can operate at the required
What are your requirements just for the power supply? Perhaps low voltage? For example 36 or 48 volts maybe up to 400 amps or so? I may know of sources for that voltage and amperage range..
Over
Terry
I'm just looking at wattage and frequency so far with the solid state approach. I've wanted to make something large. I need something that can drive a large tesla coil secondary. Depending how I wind it, anything from 70 to 120khz.
Lower frequencies will allow me to use ferrite transformers in the modulation stage. But I don't really want to go much below 80khz resonant frequency on the tesla coil secondary because if it gets too close to the audio spectrum in it's resonant frequency it won't sound good when it's audio modulated.
The voltage isn't too critical... it's going to be a pain because I'm either going to be dealing with high current or high voltage to obtain high power levels anyways.
My personal beef with the Tesla coil crowd is their failure to understand that these are transmitters!
As such - for display purposes they need to be in a GROUNDED and SHIELDED enclosure - like a metal building for example.
There are a bunch of sites and people who have driven large Tesla coils with solid state and tube gear...
...speaking only my opinion, if you have to ask these questions, you're better off not messing around with HIGH VOLTAGE & HIGH POWER.
The bottom of the secondary needs to be well grounded. As far as shielding, wind is a bigger issue than RF, at least at these frequencies. Are you doing something below 1mhz that I'm going to mess up if the building that holds this isn't metal? I doubt my 75khz tesla coil is going to bother anyone on the air from afar. It may bother the neighbors or interfere with electronics locally.
It's not like I'm trying to run a spark gap coil... those can make some real interference.
-----------------------------------------------------------------------------------------------------------------
THOUGHTS ON AUDIO MODULATION
I had an interesting idea for how to modulate this tesla coil that I definitely will need some advice on.
Rather than having to come up with a filament transformer and water cooling for a tube, I'd rather use a simpler means to accomplish the audio modulation...
the magnetic amplifier
further reading can be found here:
http://teslapress.com/magamp.pdfhttp://www.tuks.nl/pdf/Reference_Material/Magnetic_Amplifiers/Platt%20-%20Magnetic%20Amplifiers%20Theory%20and%20Application%20-%201958.pdfhttp://arizona.openrepository.com/arizona/bitstream/10150/319332/1/AZU_TD_BOX2_E9791_1956_56.pdfhttp://www.dtic.mil/dtic/tr/fulltext/u2/021818.pdfhttp://sparkbangbuzz.com/mag-amp/mag-amp.htmhttp://sparkbangbuzz.com/mag-audio-amp/mag-audio-amp.htmReally what I'm after is a magnetic modulator.
The primary of this modulatior transformer is run in series with the 1kw induction heater output. The inductance is high when there is no signal, and lowered by the addition of a signal in the other winding. Bias is controlled by the DC voltage which is applied to the "modulation winding" (unless anyone knows the actual term for this).
They actually work exactly like tubes in a certain sense, except relying on magnetic rather than electrostatic principles for switching. An image of the modulator circuit I intend to use is included, as well as a direct comparison of the magnetic amplifier to a tube.
Some design considerations for this transformer.. The primary winding must handle 36 volts at 30 amps.
I'm unsure of what the other winding should be. According to my reference material (sparkbangbuzz) a gain of 10-15 was observed in a magnetic amplifier circuit that did not use a diode on the power coil, and a gain of 1000 was observed with the addition of the diode in series with the power winding. It's impossible to know just what the gain might be until it's built. My design consideration will assume a maximum of 100 watts drive, with extra taps because I intend to use a setup which includes diodes.
The control winding on this transformer would see a DC voltage and a signal from an audio amp with 8 ohms output. So if I assume the control winding would need to handle a maximum of 100 watts and it acts as an 8 ohm load, that would be approximately 28 volts at 3.5 amps. To avoid induced AC voltage, this control winding can be two 14 volt windings with two legs hooked together such that the remaining two legs show 0 volts AC between them. DC voltage will be applied between these two points for bias, and audio will be coupled through a capacitor into these windings.
Here are some vendors I've found who sell cheaply customized ferrite transformers. Their cost is very economical for the amount of power they handle:
https://www.aliexpress.com/item/Customize-Vertical-Type-Horizontal-Type-EE55B-Primary-Pure-Copper-Inverter-High-frequency-Transformer-12V-24V-1000W/32755579418.htmlhttps://www.aliexpress.com/item/ER3501-PTH-vertical-high-frequency-switch-power-supply-transformer-set-up-transformer-push-pull/32728017774.htmlAny input is appreciated. I know this may seem like a bit of a hair-brained scheme but I think making a few custom transformers for modulation may be the easiest and cheapest way to accomplish reasonably high quality audio modulation.