Re: [TCML] SRSG "sputter"

[Joe Mastroianni <joe@xxxxxxxxxxxxxx>]

HI Gary and John,
I have made some mods to the phase control variac.  Previously, what I had been doing is using the hot lead from the input to the variac and the hot lead from the output (ignoring the neutral and ground) and using that as the variable inductor.  

I put the phase shift circuit onto the oscilloscope channel B along with wall current channel A and looked at what happened when I rotated the variac.  I got a phase shift along with a distortion of the waveform from a sinusoid to a distorted triangular shape, the peak of which maxed at about 15 degrees away from the top of the public service voltage before increases in inductance caused more voltage drop than phase shift.   After about 15 degrees I was down to about 60V and the motor lost lock. This didn't seem too out of whack with what I had been told - that I'd only get about 15 degrees.

Then I tried just using the hot and neutral from the output circuit only as in the picture on this page (http://www.hvtesla.com/phase.html) and I'm noticing about 25-30 degrees deflection before the motor loses lock.  Thanks to Brandon for the help on that one.

Now, as it turns out I have been out of the house all day on a family excursion, and only returned home this evening to do the experiments.  It's a bit late to run the coil as it would indeed wake the neighbors, so I am going to have to wait till tomorrow AM to run some experiments watching the streamers.    I did try to get a video using my iPhone yesterday in the semi-darkness, but the dark image response of that thing is pretty awful - even the streamers are hard to see in what it thinks is pitch black.  I need to get a real camera.

More to come.

With regards,
Joe


On Jul 10, 2010, at 3:08 PM, Gary Lau wrote:

> Hi Joe,
> 
> There's no way that having the gap BPS being a sub-multiple of the resonant
> frequency would affect anything.  When the SRSG phase is significantly out
> of whack, the gap fails to fire at the end of a mains half-cycle because the
> electrodes aren't aligned at the voltage peak.  So the voltage now begins to
> charge in the opposite direction.  But contrary to intuition, this energy
> isn't simply "lost".  In an L-C resonant circuit, the energy transfers
> alternately between voltage in the cap and current in the inductor.  The L-C
> circuit at this point is the cap, and the NST secondary winding, resonating
> at or near 60Hz.  Yes, you have a Larger Than Resonant sized cap, but when
> NST secondary currents flow through capacitive loads, we think that the
> current limiting shunts saturate, and ferroresonance kicks in and strange
> stuff happens, permitting at or near mains resonance.  Bottom line, the
> energy isn't lost, but when the voltage reverses, then charges to the
> opposite polarity, it will reach a FAR higher voltage than on the previous
> half-cycle, enough to break down a safety gap or insufficient RSG
> insulation.
> 
> As John said, it's not possible that the cap can carry a charge between
> bangs.  Once a spark gap fires, it won't stop firing until pretty much all
> of the energy has been dissipated.  This happens pretty fast, and the fact
> that the electrodes are spinning quickly doesn't matter.
> 
> Now that your gap timing is in the ballpark, can you describe what happens
> as you sweep the phase adjustment Variac through its range?
> 
> Regards, Gary Lau
> MA, USA
> 
> On Sat, Jul 10, 2010 at 12:09 AM, Joe Mastroianni <joe@xxxxxxxxxxxxxx>wrote:
> 
>> Hi All,
>> Well, indeed the problem was curable by advancing the timing on the rotor
>> about 30 degrees.  Now I can bring it up to full power - BUT - I would say
>> that on full power the arcs aren't as large as they were when I had the
>> "sputter" problem.  After doing a bit of reading I've come to the conclusion
>> that the sputter was indeed some off-timing resonance issue where I was not
>> entirely discharging my MMC bank.   Perhaps it was some out-of-control
>> ringup issue that the safeties were saving me from, with the pulses hitting
>> the cap bank at some multiple of the resonant frequency.  I measured my
>> Thus the safeties were firing to offload the additional charge.
>> 
>> Java TC suggests my resonant freq is around 130khz but it wouldn't surprise
>> me if it was closer to 120khz, which, perhaps, would cause some issues at
>> 120bps under certain conditions.  It would take me going out and getting
>> some HV probes for my scope to see it for myself...
>> 
>> Meanwhile, it works now fine.
>> 
>> Of course, this will not stop me from trying the other SRSG designs.  I'm
>> too curious.
>> I'm also going to try an ARSG, as I do like the sound.... ;-)
>> 
>> Joe
>> 
>> 
>> 
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla