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Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
Now I am not sure whether that comment about my TC being "crappy" was meant to be an insult, or just being realistic.
However, instead of firing it up as is I attached an external oscillator to see if everything is working, and figured out that the current feedback is not. I have two 30 turn CTs in series. If I wire them up in parallel ( i.e. as two independent single CTs, they both give a reasonable sqarewave on the output. If I have the two in series, there is no proper output, just some noise. How can this be? Everyone seems to use cascaded CTs, so surely two in series should work better than a single one? Primary current is probably not very high, since I am driving it far off resonance and at only 30V, getting only 1cm sparks from the coil. Still, the feedback signal should be there, no?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
You are sure you have wired the CTs properly? How are they wired up? I even use a cascaded CT pair for a measurement device with my scope, and it works just great. It does tend to pick up switching noise, but i use that as a benefit so that i can tell where im switching relative to the current .
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
You don't need to cascade the current transformers. Instead of winding (2) 30 turn transformers, just wind a 100:1 single one. Using the feedback circuit Steve uses, this is good up to at least 1000A peak current.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
Steve Ward wrote ...
You are sure you have wired the CTs properly? How are they wired up? I even use a cascaded CT pair for a measurement device with my scope, and it works just great. It does tend to pick up switching noise, but i use that as a benefit so that i can tell where im switching relative to the current .
Is there any way to wire them improperly? I am now running the coil with just one 30T transformer, because that's what seems to be working for me. It is probably not good to do this, way too much current through the zeners. It works well if I run the coil off 24V, when it gives about 1" of sparks. If I apply full mains voltage, it stops oscillating, but I don't blow any components. Weird...
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yet another DRSSTC - reality check
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