Originally posted by yampa
Triacs allow RMS power and voltage control - you can mess with the waveform produced by the power supply. You can certainly apply PWM to a triac.

No, no, you can't. Once you switch it on, it's on. There's no turning it off. You can't PWM with one whatsoever, in the proper sense. The only "PWM" you can do is delay where in the incoming AC waveform you switch the triac on, and that's old fashioned phase control. You can't control voltage either. TRIACS can't be modulated like a transistor or FET, you fire them and they're on. That's it. No level control at all. And once on, the only way to turn it off is to wait for the current to fall to the critical level.

Who is to say that knowing the right way to switch the output doesn't facilitate a reaction? Perhaps he is switching to create some kind of harmonic? Or maybe wants a deliberately noisy signal, so switches it at random?

Me. I'm the one to say it. The output of a TRIAC is on, and once on, it's on until the current through it falls to near zero. There's no special way to do it. It's fired, or it isn't.

eta: and what you get out of it when you're phase controlling with AC isn't a sine wave - diddling the firing point in the phase gives you control over RMS power, but it's not a nice sine wave anymore, it's pretty nasty looking. Fine for a motor or an incandescent light, not so good for other things...

etaa: and the waveform you get is textbook typical for phase control using a TRIAC on AC. You can't make secret new waveforms with it.

You can modulate the signal with a triac (plus other components) if you synchronize to zero crossing. I guess that isn't true PWM waveform generation though.

Rossi's experiment had a three phase input originally, and we don't know the frequency of the input PSU. I think you could create some interesting signals with a high frequency, three phase AC controlled by triacs?

We don't have details of what is in the control box and we have no idea which signals/waveforms are and aren't useful for facilitating unknown reactions.

Apparently the later version no longer uses triacs or three phase output:

The E-Cat HT2's power supply departs from that of the device used in December in that it is
no longer three -phase, but single-phase: the TRIAC power supply has been replaced by a control
circuit having three -phase power input and single-phase output, mounted within a box, the
contents of which were not available for inspection, in as much as they are part of the
industrial trade secret. But the main difference between the E-Cat HT2 and the previous model
lies in the control system, which allows the device to work in self -sustaining mode, i.e. to
remain operative and active, while powered off, for much longer periods of time with respect to
those during which power is switched on. During the test experiment we observed that, after an
initial phase lasting about two hours, in which power fed to the resistor coils was gradually
increased up to operating regime, an ON/OFF phase was reached.
In the ON/OFF phase, the resistor coils were powered up and powered down by the control system at
regular intervals of about two minutes for the ON state and four minutes for the OFF state. This
operating mode was kept more or less unchanged for all the remaining hours of the test.

Originally posted by yampa
You can modulate the signal with a triac (plus other components) if you synchronize to zero crossing. I guess that isn't true PWM waveform generation though.

Nah, what you have then is jelly bean phase control. It's not up to "secret waveforms", unless classic TRIAC phase control is secret.

Rossi's experiment had a three phase input originally, and we don't know the frequency of the input PSU. I think you could create some interesting signals with a high frequency, three phase AC controlled by triacs?

If you're handling the power upstream to the extent that you're supplying 'high frequency three phase AC', you don't need the TRIACs, just make it what you want. That's the issue I have with humming in 'TRIACs' as a magic bean here, it sounds sciency but it's not what you'd use in this case. eta: TRIACs aren't really that good with high frequencies either, you've got a really big volume you have to sweep clean of charge carriers before they turn off, the higher powered the TRIAC the more sluggish they are.

We don't have details of what is in the control box and we have no idea which signals/waveforms are and aren't useful for facilitating unknown reactions.

What I'm saying is that if he needed weird waveforms or signals, he could not have gotten them with a TRIAC, and I see his invoking them here as a sort of pseudo-sciencey smoke screen of cool terms. If you tell me with a straight face you are making 'industrial secret waveforms' with TRIACs, you are a liar, they are not suitable for that purpose.

Originally posted by Bedlam

What I'm saying is that if he needed weird waveforms or signals, he could not have gotten them with a TRIAC, and I see his invoking them here as a sort of pseudo-sciencey smoke screen of cool terms. If you tell me with a straight face you are making 'industrial secret waveforms' with TRIACs, you are a liar, they are not suitable for that purpose.

I think this is your own bias about what constitutes 'weird waveforms' showing. I don't see Rossi invoking anything about secret waveforms - I see the author of the papers summarising the resistor heater control system as a secret. You can fit the idea of 'waveform' to several levels of signal control here and we don't know what the authors of the paper meant by this.

It is my own interpretation that he is using the power control to raise the complexity of the emission from the resistor coils. I can think of a few different ways to use triacs to influence the charge emission from those heater coils.

I think your ideas about what triacs can and can't be used for are deliberately limited because you are not genuinely thinking about nickel powder + hydrogen heat engines.