There once was a time when it was believed that in order to extract
the maximum power from an NST, the cap should be mains-resonant.
Experience and measurement now shows this to be not true; a cap value
that is larger than resonant is where the maximum power is drawn.
And perhaps more importantly, there is a hazard with using a
mains-resonant cap. Should the spark gap be set too widely, the cap
will charge to successively higher and higher voltage with each mains
half-cycle if the gap does not fire, until something, typically the
NST insulation, breaks down. Choosing a LTR cap value lowers the
degree to which the cap will ring up on successive half-cycles.
There is NO situation where a mains-resonant cap is ideal. Use a
value between 1.5-2.0 times the mains-resonant value.
A sync RSG needs to use a larger cap value than a static gap because
the sync break rate (120BPS) is lower than a static gap typically
fires at. It is basically not possible to get consistent 120BPS
operation with a static gap. Nothing to do with Q.
Regards, Gary Lau
MA, USA
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Andrew Robinson
Sent: Monday, July 13, 2009 6:33 PM
To: tesla@xxxxxxxxxx
Subject: [TCML] Tank Capacitor
Whats the difference between the static gap LTR Cap and a resonant
cap? When do you use a resonant cap?
Should we use the resonant cap (0.0066uF) or the LTR static gap cap
(0.0099uF) (12/30 NST on 60Hz)
Why is there a different cap value for a SRSG. Is this because the
cap is designed to achieve max Q at the peak of each waveform
whereas with a static gap your going for max usable Q.
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