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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