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Re: More Tuning/Debugging Next



In a message dated 96-09-09 02:54:48 EDT, you write:

<< Jim and Richard,
 > 
 > Thanks for the advice.  I had been using three 2000 watt oven elements
(each
 > in parallel) in parallel with the welder which is ballasting the pole pig.
 >  This is a 5 KVA pig that I have been running up to 7 or 8 KVA.  As I
 > mentioned, with my recent changes in the primary circuit the gaps will not
 > fire with the old configuration and the system would only work well with
the
 > resistive elements unplugged - i.e. welder only.  What would you suggest
 > here?  Just trying two elements then one element in parallel with the
welder
 > and check system performance?  I have up to six or seven 2000 watt
elements
 > that can be used.  Is there any value in trying the elements in series
with
 > the welder?  I did try that in the old configuration and performance went
 > down.
 > 
 > Thanks,  Ed Sonderman
 
 Ed,
 
 There is definately something interesting going on in your system!
 
 What voltage rating is the "primary" of your 5 KVA pig? By any chance,
 are you running 240 Volts into a 120 Volt winding to get 14.4 KV out of
 a 7.2 KV pig??  You may be saturating your pig... When this occurs, the
 output voltage will no longer be sinusoidal. The "tops" of the sinusoid
 flatten out, and you may not be able to charge the caps to the voltage
 necessary to break down the gaps. Jim's system saturates his pig, but it
 seems to run OK (with perhaps some fairly high voltage spikes as the pig
 comes into/goes out of saturation in series with the ballast...).
 
 If you have an old 15 KV neon laying around, try tying the secondary of
 the neon across the pig output, and scoping or taking a voltage
 measurement on the primary of the neon while increasing the variac
 setting. This is a "poor-man's" equivalent to a potential transformer.
 If you see signs of significant "flattening" of the sinusoidal tops on a
 scope, or any marked flattening of output vs input voltage, pig
 saturation may be what you're fighting. 
 
 A possible scenario:
 When you remove the resistors, you reduce the real primary power being
 dissipated in the core as well as reduce the damping on the ballast.
 Near the zero crossings on the AC input, the pig comes out of
 saturation, and the ballast can now "dump" its stored energy into the
 secondary circuit, helping to charge the caps (with potentially large
 voltage spikes??). Removing the resistors also reduce the depth of
 saturation when the gaps do fire. This may allow more energy from the
 pig primary and ballast to transfer to the secondary and to your cap.
 Because of the smaller core size, this may be more of a problem on 5 or
 10 KVA transformers than on Richard Quick's re-wired 25 KVA beastie.
 
 Jim - could your MicroSim SPICE model be modified to simulate the
 effects of pig core saturation?? 
 
 Good luck, and safe coilin' to ya! ;^)
 
 
 -- Bert --
  >>

Bert,

My pig is rated at 5KVA at 14,400 volts.  I measured it at 65:1.  I am
supplying 220 volts to the 220 volt input (output actually).  The scope would
be a good idea but I don't have one.  Next time I set it up I will try
different combinations of resistive load in parallel with the welder.  If
this doesn't produce any good results, I will try the resistive load in
series with the welder.

Thanks,  Ed Sonderman