Idea: harmonically driven TC
Crunchy Frog, Tue Aug 24 2010, 04:11AMSo I had a thought. What if one were to drive a TC with the primary resonating at half (or maybe less) the secondary's Fres? I ran across this accidentally in a simulation, and it seems to work in the simulator, so why not in real life?
This would seem to help with (for example) headaches getting IGBTs to switch at high frequencies.
I don't have a setup to test this on, but maybe someone else here does.
Re: Idea: harmonically driven TC
radiotech, Tue Aug 24 2010, 04:49AM
TV flybacks have been doing this for years ,driven at 15734 Hz and resonating at the 3rd harmonic and later the 5th harmonic.
The makers are very particular in the winding design and there is considerable difference between solid state TV's and the tube ones.
radiotech, Tue Aug 24 2010, 04:49AM
TV flybacks have been doing this for years ,driven at 15734 Hz and resonating at the 3rd harmonic and later the 5th harmonic.
The makers are very particular in the winding design and there is considerable difference between solid state TV's and the tube ones.
Re: Idea: harmonically driven TC
teravolt, Tue Aug 24 2010, 04:51AM
you could do this but the pulse width would have to be equal to 1/2 cycle so your tesla f=200khz then your pulse width is 5us. A igbt can do about 100khzs max so your wave form would be 100khz or a multipul of 200khz with a 5us pulse width. does this make sense
teravolt, Tue Aug 24 2010, 04:51AM
you could do this but the pulse width would have to be equal to 1/2 cycle so your tesla f=200khz then your pulse width is 5us. A igbt can do about 100khzs max so your wave form would be 100khz or a multipul of 200khz with a 5us pulse width. does this make sense
Re: Idea: harmonically driven TC
radiotech, Tue Aug 24 2010, 06:23AM
Crunchy Frog wrote "I ran across this accidentally in a simulation, and it seems to work in the simulator,"
Did your simulation allow changing the coefficient of coupling?
That image in reply to Dingo 27's thread gives some math on the effect of coupling governing which 2 frequencies will be present in both the primary and secondary of a drtc. Also EastVoltResearch mentioned the effect of the arc's capacity changing fres.
"I don't have a setup to test this on, but maybe someone else here does. "
Of course a spectrum analyser would be nice but a simple investigation can be done with the most simple tool-a wavemeter which consists of a variable condenser, from an AM radio and an inductance to resonate around 200-400 kHz , perhaps 300 uHy. A dmm connected to a diode tap on the coil will indicate resonance and the dial of the variable cap can be marked off in frequency.
radiotech, Tue Aug 24 2010, 06:23AM
Crunchy Frog wrote "I ran across this accidentally in a simulation, and it seems to work in the simulator,"
Did your simulation allow changing the coefficient of coupling?
That image in reply to Dingo 27's thread gives some math on the effect of coupling governing which 2 frequencies will be present in both the primary and secondary of a drtc. Also EastVoltResearch mentioned the effect of the arc's capacity changing fres.
"I don't have a setup to test this on, but maybe someone else here does. "
Of course a spectrum analyser would be nice but a simple investigation can be done with the most simple tool-a wavemeter which consists of a variable condenser, from an AM radio and an inductance to resonate around 200-400 kHz , perhaps 300 uHy. A dmm connected to a diode tap on the coil will indicate resonance and the dial of the variable cap can be marked off in frequency.
Re: Idea: harmonically driven TC
Dr. Dark Current, Tue Aug 24 2010, 08:47AM
I think it would only work at f0/3, f0/5 etc. because a square wave has odd harmonics. This would probably work better for a DRsstc, because in a SSTC the primary current would ramp up to a huge value because of the primary's low inductance.
Dr. Dark Current, Tue Aug 24 2010, 08:47AM
I think it would only work at f0/3, f0/5 etc. because a square wave has odd harmonics. This would probably work better for a DRsstc, because in a SSTC the primary current would ramp up to a huge value because of the primary's low inductance.
Re: Idea: harmonically driven TC
Hazmatt_(The Underdog), Wed Aug 25 2010, 02:15AM
Actually, the odd part is the secondary will ring up when the primary is at 2/3 Fo. I was doing some sweeps with my power amps and noticed this, but I can't account for it just yet in simulation, and I need to rebuild my poweramp. I may post more on that later, I dunno, it's hard to do this stuff and work full time.
Hazmatt_(The Underdog), Wed Aug 25 2010, 02:15AM
Actually, the odd part is the secondary will ring up when the primary is at 2/3 Fo. I was doing some sweeps with my power amps and noticed this, but I can't account for it just yet in simulation, and I need to rebuild my poweramp. I may post more on that later, I dunno, it's hard to do this stuff and work full time.
Re: Idea: harmonically driven TC
radiotech, Wed Aug 25 2010, 03:05AM
Hazmatt the Underdog wrote: Actually, the odd part is the secondary will ring up when the primary is at 2/3 Fo.
Yes but that usually sparks up (sic) a furious debate about whether or not subharmonics do in fact exist.
radiotech, Wed Aug 25 2010, 03:05AM
Hazmatt the Underdog wrote: Actually, the odd part is the secondary will ring up when the primary is at 2/3 Fo.
Yes but that usually sparks up (sic) a furious debate about whether or not subharmonics do in fact exist.
Re: Idea: harmonically driven TC
Coronafix, Sun Aug 29 2010, 12:03AM
It's called a Perfect Fifth in music! i don't see what the debate could possibly be about.
Coronafix, Sun Aug 29 2010, 12:03AM
It's called a Perfect Fifth in music! i don't see what the debate could possibly be about.
Re: Idea: harmonically driven TC
dex, Sun Aug 29 2010, 05:36PM
I've heard only of higher harmonics (from Fourier analysis).Would you be kind to define and specify meaning of "subharmonics"? I've done some PSPICE simul for DRSSTC excited by 2/3 Fo of secondary natural frequency, with typical coupling of 0.15.All I can see from it is that the power transfer is poor in comparison with Fo excitation...
dex, Sun Aug 29 2010, 05:36PM
radiotech wrote ...
Hazmatt the Underdog wrote: Actually, the odd part is the secondary will ring up when the primary is at 2/3 Fo.
Yes but that usually sparks up (sic) a furious debate about whether or not subharmonics do in fact exist.
Hazmatt the Underdog wrote: Actually, the odd part is the secondary will ring up when the primary is at 2/3 Fo.
Yes but that usually sparks up (sic) a furious debate about whether or not subharmonics do in fact exist.
I've heard only of higher harmonics (from Fourier analysis).Would you be kind to define and specify meaning of "subharmonics"? I've done some PSPICE simul for DRSSTC excited by 2/3 Fo of secondary natural frequency, with typical coupling of 0.15.All I can see from it is that the power transfer is poor in comparison with Fo excitation...
Re: Idea: harmonically driven TC
radiotech, Sun Aug 29 2010, 07:21PM
The debate centers around the fundamental. If a harmonic is a higher multiple of the fundamental then subharmonics are just an as yet not undiscovered fundamental. In Helmholtz, (Sensations of Tone), he states the G S Ohm was the first to declare that there is no form of vibration that will give rise to no harmonic upper partial tones,and therefore will consist soley of the prime tone.
The electrical cases are found in apparent subharmonics in non-linearalities especially in AC ferrite magnetizations. Hence Hazmatt's comment, which is valid in that they do appear. Squedging is common is a lot of stuff, especially oscilators. But he was driving the flyback with something that made it produce multiple signals. his conclusion 3/5 Fo was based on the fact that this was 3/5 of what is ' should' have ringing at. The key word in his send was the word coupling because that is the variable known since spark transmitters
of adjustable to regulate multiple modes.
Back to Hemholtz. .. this a form of vibration pecular to pendulums and tuning forks.. we will call these pendular vibrations, or since they cannot be be analysed into a compound of different tones, simple vibrations.
Helmholtz used an early oscilloscope A smoked drum onto which a stylus made a mark as it rotated.
radiotech, Sun Aug 29 2010, 07:21PM
The debate centers around the fundamental. If a harmonic is a higher multiple of the fundamental then subharmonics are just an as yet not undiscovered fundamental. In Helmholtz, (Sensations of Tone), he states the G S Ohm was the first to declare that there is no form of vibration that will give rise to no harmonic upper partial tones,and therefore will consist soley of the prime tone.
The electrical cases are found in apparent subharmonics in non-linearalities especially in AC ferrite magnetizations. Hence Hazmatt's comment, which is valid in that they do appear. Squedging is common is a lot of stuff, especially oscilators. But he was driving the flyback with something that made it produce multiple signals. his conclusion 3/5 Fo was based on the fact that this was 3/5 of what is ' should' have ringing at. The key word in his send was the word coupling because that is the variable known since spark transmitters
of adjustable to regulate multiple modes.
Back to Hemholtz. .. this a form of vibration pecular to pendulums and tuning forks.. we will call these pendular vibrations, or since they cannot be be analysed into a compound of different tones, simple vibrations.
Helmholtz used an early oscilloscope A smoked drum onto which a stylus made a mark as it rotated.
Re: Idea: harmonically driven TC
dex, Tue Aug 31 2010, 12:22PM
Thanks for the reply.I didn't know of Helmholz work you mention.
Opposed to that tesla coils are quite a linear machines.
The thing which may be confused with "subharmoonic" ,I think, are perhaps frekquencies of beats which are always present in more or less tuned 2 circuit tc system.
dex, Tue Aug 31 2010, 12:22PM
Thanks for the reply.I didn't know of Helmholz work you mention.
radiotech wrote ...
The electrical cases are found in apparent subharmonics in non-linearalities especially in AC ferrite magnetizations.
The electrical cases are found in apparent subharmonics in non-linearalities especially in AC ferrite magnetizations.
Opposed to that tesla coils are quite a linear machines.
The thing which may be confused with "subharmoonic" ,I think, are perhaps frekquencies of beats which are always present in more or less tuned 2 circuit tc system.
Re: Idea: harmonically driven TC
Steve Conner, Tue Aug 31 2010, 09:03PM
Back in the days of OLTCs we used to experiment with extremely high break rates. The coil would always work best if you adjusted the break rate so that it was a submultiple of the resonant frequency. As you adjusted the break rate, you'd see peaks and nulls in the spark output.
I think Tesla himself observed this back in the 1890s.
The Tesla resonator itself is linear, but the drive waveform, whether it comes from solid-state circuitry or a spark gap, is usually a square wave or some sort of rectangular pulse. The square wave contains the odd harmonics, a pulse wave with other than 50% duty contains all of the harmonics. Whenever a harmonic of the drive matches the resonant frequency of the Tesla resonator, you'll get sparks of some sort.
Steve Conner, Tue Aug 31 2010, 09:03PM
Back in the days of OLTCs we used to experiment with extremely high break rates. The coil would always work best if you adjusted the break rate so that it was a submultiple of the resonant frequency. As you adjusted the break rate, you'd see peaks and nulls in the spark output.
I think Tesla himself observed this back in the 1890s.
The Tesla resonator itself is linear, but the drive waveform, whether it comes from solid-state circuitry or a spark gap, is usually a square wave or some sort of rectangular pulse. The square wave contains the odd harmonics, a pulse wave with other than 50% duty contains all of the harmonics. Whenever a harmonic of the drive matches the resonant frequency of the Tesla resonator, you'll get sparks of some sort.
Re: Idea: harmonically driven TC
radiotech, Tue Aug 31 2010, 10:04PM
Steve McConner wrote : As you adjusted the break rate, you'd see peaks and nulls in the spark output.
Two things, if the break rate was a submultiple of the coil Fr that would have been after the fact that the coil's Fr was already known, and not that it was originating Fr/n. If that was the case, then the coil would have been resonating at a harmonic of the break rate.
From Admiralty Handbook (1925) By using a very short gap and using some means of restoring gap insulation, such as a rotary spark gap, it may be possible to obtain 2 sparks per half cycle (of the AC source driving) The thing they are talking about here
covers issues (need for 'Terry Filters") and damping which decides whether or not the spark (which is the sole source of the RF that fires the coil) will drive the coil at the natural resonance.
radiotech, Tue Aug 31 2010, 10:04PM
Steve McConner wrote : As you adjusted the break rate, you'd see peaks and nulls in the spark output.
Two things, if the break rate was a submultiple of the coil Fr that would have been after the fact that the coil's Fr was already known, and not that it was originating Fr/n. If that was the case, then the coil would have been resonating at a harmonic of the break rate.
From Admiralty Handbook (1925) By using a very short gap and using some means of restoring gap insulation, such as a rotary spark gap, it may be possible to obtain 2 sparks per half cycle (of the AC source driving) The thing they are talking about here
covers issues (need for 'Terry Filters") and damping which decides whether or not the spark (which is the sole source of the RF that fires the coil) will drive the coil at the natural resonance.
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