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Re: [TCML] SRSG "sputter"
HI Gary -
Ok - some measurements available on YFrog
<http://yfrog.com/13t2qj> This is the maximum phase shift I've measured. What you're seeing is the sine wave from utility power against a distorted triangular wave. This is the voltage between my household hot lead (black) and the household neutral lead (white).
That triangle wave is measured from the point where the variac L output connects to the run cap and feeds into the motor relative to the neutral connection (white). So the motor is across the neutral and this point which I am measuring. Notice the maximum phase shift appears to be between 1.2 and 1.6ms (lets say 1.4). That would put the max phase shift, as measured from the power supplies, at 360*1.4/16.67 = ~30 degrees.
Now, we could argue that the waveform from the power supply going into the motor may somehow not relate directly to the motor timing angle. Ok, I would kind of wonder why that might not be so, but for the sake of argument I have added these videos.
I attached 2 rectangular neodymium magnets to 2 of the rotating tungsten rods on the SRSG wheel with wire ties. I then wrapped 20 turns of 26gauge magnet wire around one of the stationary tungsten electrodes.
The first video shows 2 waveforms. <http://yfrog.com/0jrelmotdrivez> Channel A is the power feeding the motor, out of the variac/cap circuit. Notice how that waveform distorts as the variac L is progressed from "0" to about 1/2 way. Channel B is the voltage "blip" taken off the coil as the magnets rotate past. I think we can presume TDC is when the magnet/timing waveform crosses "0". I rotated the variac until the motor began to lose lock (you can hear it in the background, and see the waveform begin to oscillate). Notice the magnet pulses do not change phase with respect to the power supply to the motor, even though that voltage waveform begins to distort when the variac L is moved off "0".
The second video shows 2 waveforms. <http://yfrog.com/bcrelutilz > Channel A once again is public service power, taken from the feed to the coil. Channel B is the voltage taken off the 20-turn magnet wire, measuring the passage of the magnets attached to the spinning tungsten electrodes. Here you can see the phase change quite dramatically, and it's clearly about 30 degrees before the motor loses lock.
Apologize for the video quality - this is taken from my iPhone as I kneel beside the coil and rotate the variac.
Hope this data is useful.
Cheers,
Joe
On Jul 11, 2010, at 9:03 AM, Gary Lau wrote:
> Hi Joe,
>
> I didn't understand the before and after circuit configurations of your
> phase Variac. A Variac is a 3-terminal device - Call the two ends of the
> inductor A (hot) and C (neutral), and call the variable tap B. Mains ground
> only goes to the case for safety (and should be used). In the phase shift
> circuit, we want just a 2-terminal variable inductor, so use terminals A & B
> or B & C (plus the case ground).
>
> If I understand your post, you previously used "the hot lead from the input
> to the variac and the hot lead from the output". Terminals A & B.
>
> You then switched to "the hot and neutral from the output circuit".
> Terminals B & C?
>
> Both configurations should go from 0-100% of the total inductance, the only
> difference being that in one the full inductance is at the CW end and the
> other is at the CCW end. I don't think there should have been any
> difference in total phase shift achievable, if I understood the
> configurations correctly.
>
> You mentioned seeing phase shifts of 15 and 25 degrees. Since 360 degrees
> is 16.67 msec, 15 degrees is only 0.69 msec, and 25 degrees is 1.16 msec. Is
> this correct? It would be good to verify that the motor shaft varies by the
> same amount.
>
> Regards, Gary Lau
> MA, USA
>
> On Sun, Jul 11, 2010 at 1:54 AM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:
>
>> 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
>>>>
>>>>
>>>>
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