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Re: Other changes
Tesla List wrote:
>
> >From Esondrmn-at-aol-dot-comTue Sep 17 22:44:43 1996
> Date: Tue, 17 Sep 1996 17:16:49 -0400
> From: Esondrmn-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: Other changes
>
> In a message dated 96-09-14 17:48:13 EDT, you write:
>
> << Ed,
>
> Not Likely. The grounding system would influence coil behavior AFTER the
> gaps fired, but should have no influence on the initial breakdown
> voltage of the gaps. [A note: over the long term you may want to
> re-verify the integrity of your ground since the salt solution may
> attack the galvanized steel due to the shorted battery (galvanic
> corrosion) formed by the copper groundrod and the flashing.]
>
> Does your welder start growling when your gaps are NOT firing, and does
> it seem to rather abrubtly increase in volume as you slowly increase the
> variac setting? What is minimum gap length of your static and rotary
> gaps respectively? If your gaps begin sporadically firing at relatively
> low settings, and you hear growling at relatively low voltage settings
> you may be resonating your tank cap/ballast. This condition can make the
> coil run VERY well while in 60 Hz resonance, and significantly less so
> when you increase/decrease ballast inductance and drive the system out
> of the peak.
>
> Recent changes you've made to the system (especially removing the
> ballast resistors) increase the 60 Hz Q of the system, making the region
> of 60 Hz resonance significantly narrower but much "hotter" when you hit
> it. Although Tank/Ballast resonance can make a coil run VERY well (even
> "synergistically" so...), it CAN over-stress a tank cap particularly
> when used with a rotary gap. The peak cap voltage will rise to QxVout
> unless the cap shorts or the primary gaps or safety gap clamp it to a
> lower (nondestructive) value. With no resistors across your ballast
> inductor, your 60 Hz Q may be quite high. This may take out your cap if
> your rotary misfires...
>
> Try measuring the pig input voltage with a CHEAP multimeter. Do you see
> any differences in voltage for a given variac setting when the coil is
> working versus when its not? Do you see any sudden increases? By taking
> and recording a number of strategic measurements and noting any other
> behavioral differences between when the coil is working properly and
> when its not, we should be able to get to the bottom of this!
>
> Safe (but intermittent) coilin' to ya! :?)
>
>
> -- Bert -- >>
>
> Bert,
>
> The minimum gap length for the rotary is determined by the uneven height of
> the acorn nuts and runout of the wheel. Last time I adjusted it I think I
> had about .020 clearance between the fixed electrode on one side and somewhat
> less on the other side. A good estimate would be .030 to .040. The static
> gap in series is presently using three gaps of .030 each.
>
> You mentioned the tank capacitor can be overstressed due to 60 HZ resonance -
> remember I did just blow one of the C.P. capacitors. It was rated at 15KV,
> the current cap is the same only rated at 20KV. I do have analog panel
> meters monitoring the pig input current and voltage.
>
> My notes from the last couple of runs show when the gaps would fire, the
> voltage and current readings looked normal - this is with the resistive load
> disconnected. With the resistive load connected in parallel with the welder,
> the pig input voltage was normal (nice, smooth control with the variac) but
> the primary current was low and sputtered up and down as the gaps would just
> barely fire.
>
> I will check on the primary readings again and note welder and pig growling
> next time I get it set up.
>
> Thanks for the ideas, Ed Sonderman
You're welcome!
By my calculations, you're not able to jump a gap which is about 130
mils long(!?). This would seem to imply that you're not even getting 5
KV across the gap. Could you have a bad connection in the short-circuit
path on the secondary of the welder??
-- Bert --