Test Coil, RCD not happy

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Original poster: "Chris Rutherford" <chris1@xxxxxxxxxxxxxxxxxxx>

Hi All,

I finally gave up on my MOT DC multiplier having fried my HV smoothing 
chokes, which where infact only flash tested to 1.5KV by the manufacturer, 
and then subjected to a continuous RF 2.5KV, no wonder they died, 
transformer oil would have only delayed the inevitable.  I purchased 4 NSTs 
from "Specialist Neon Signs" in the UK, the 10KV 25ma unprotetected variety 
at a 40% discount :-).  I think most manufacturers are trying to get rid of 
LF NSTs as new legislation is saying that switch mode must be used as they 
are more efficient.

Having piled 4 copper pipes in to the garden I started to test my coil.

I took the following measurements, using a scope and signal generator.

Pri, C=10nF, RSG short circuited, one side of pulse cap to ground and sig 
gen and osc on other side I see a resonant frequency at 285KHz.  9 turns, 
pancake, start radius=10 cm and radius=26 cm cable dia= 0.5cm.  These 
figures in JAVATC produce fo= 282.31KHz so I'm happy with the 1% error.

Sec Top Spere 25 cm, coil 10cm*77cm, 1400 turns.
measured fo by connecting osc and sigen to base of TC, fo=250KHz.  These 
figures in JAVATC produce fo= 252.9KHz so I'm happy with the 1% error.

With these frequencies I have a 10% dis-tuned system.  Unfortunately, I can 
only use one of my NSTs, as when I bring the others in I trip my RCD.  I 
don't have a variac so it could be a transient that could be avoided by 
cranking the power up slowly?

Is 10% out of tune enough to trip a 30ma RCD?  I have a good RF earth using 
4 copper pipes, but I do have a long earth cable (10 meters) measuring 
approx 1 ohm.  Is this OK?  Any ideas how to stop my RCD from firing?

Thanks

Chris

->An RCD circuit breaker is the same idea as a GFI circuit breaker<-