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Musical microwave oven transformer?

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LAN_403

teslarevolution

Sun Jul 07 2013, 10:37PM

Registered Member #16903 Joined: Thu May 09 2013, 08:00PM
Location: Sumter, SC
Posts: 23

ok i've had this idea but never tried doing it but is it possible to rectify the mains voltage feed it in to a mot through a mosfet and switch the mosfet on and off to make music much like a tesla coil?

HV Enthusiast

Sun Jul 07 2013, 11:19PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

If you rectifiy the mains voltage and feed it through a MOT, you are essentially putting DC into a transformer which is not possible.

If you mean to modulate the input voltage to a MOT with audio frequencies, that will not work either. The core of a MOT is designed for 50/60Hz operation. You will saturate the core with high frequency (audio) input signals.

You can rectify the output of a MOT, and then modulate that DC voltage. There are many types of high side modulation schemes available for that type of set-up. Mostly used with vacuum tube amplifiers.

Also, that's basically how high-side vacuum tube audio tesla coils work. Generally an audio modulation transformer is used at the plate voltage side with a push-pull circuit to modulate the plate voltage to the tubes. Sue Gaeta did a very nice demonstration of this about 10 years ago. If you search for her name, you may be able to find some information about her high side VTTC audio modulation coil.

MR-ZAPPY

Tue Jul 09 2013, 09:11PM

Registered Member #16018 Joined: Fri May 03 2013, 07:19PM
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Posts: 53

You could just modulate a flyback which would be much simpler

Dr. Dark Current

Wed Jul 10 2013, 08:40AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

The core will not saturate with high frequencies. The problem is that the arc would go out all the time during zero crossings and silent passages, you need an arc with idle power which is able to keep it burning. This is possible only by modulating a DC voltage, or with a carrier wave.

HV Enthusiast

Wed Jul 10 2013, 02:30PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Uh, the core WILL saturate with high frequencies. You put 20kHz in a closed core that's designed for 50/60Hz, it WILL saturate.

Tetris

Thu Jul 11 2013, 04:29PM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

I think even if you managed to do that without destroying the MOT, it would be drowned out by 60/50hz hum.

Dr. Dark Current

Fri Jul 12 2013, 01:31PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
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Posts: 3384

EasternVoltageResearch: The core will not saturate with higher frequencies, but with lower ones than the core was designed to work with (while keeping the same voltage and waveform). At a very high frequency, the flux density in the core will be very small. Psi = integral of V, where psi = N * fi is the linkage flux, "fi" is magnetic flux in the core, "N" is number of turns.

However, there would be another problem at high frequencies, and that is the winding capacitance and leakage inductance, which form a resonant low-pass filter and the high frequency would not get through the transformer.

HV Enthusiast

Fri Jul 12 2013, 02:42PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Dr. Dark Current wrote ...

EasternVoltageResearch: The core will not saturate with higher frequencies, but with lower ones than the core was designed to work with (while keeping the same voltage and waveform). At a very high frequency, the flux density in the core will be very small. Psi = integral of V, where psi = N * fi is the linkage flux, "fi" is magnetic flux in the core, "N" is number of turns.

However, there would be another problem at high frequencies, and that is the winding capacitance and leakage inductance, which form a resonant low-pass filter and the high frequency would not get through the transformer.

Yes, you are correct. I stand corrected.

teravolt

Fri Jul 12 2013, 04:58PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

if you want to just try something you could try what Zilipoper did

using a full or half bridge and modulate it either with frequency or modulate it like a DRSSTC

the mad scientist

Tue Jul 23 2013, 06:30PM

Registered Member #3768 Joined: Tue Mar 22 2011, 12:46AM
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Posts: 107

ASHPoD wrote ...

I think even if you managed to do that without destroying the MOT, it would be drowned out by 60/50hz hum.

Exactly, using a MOT for this is somewhat inpractical.

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