[Prev][Next][Index][Thread]

Re: Primary Resonant Rise

Malcom:
	Just a comment.  The leakage inductance measured at low
voltage will be different from that measured at normal oprating
voltage and core flux density.  A few years ago I was operating
a coil with a 15 kV, 60 ma transformer and 0.006 mfd capacitor.
I found that as I ran the primary voltage up from zero I reached
a point where resonance occurred, and the secondary voltage would
rise very suddently to several times the voltage at a slightly
lower primary voltage.  
	Good thing I had a gap across the transformer to limit
the voltage, as otherwise I would have blown up my voltmeter 
(or the transformer).  There was a very noticeable hysteresis
in the effect, as the variac setting had to be reduced quite
a bit before the sparking stopped.  
	I have never re-run this experiment, but you might find
it interesting.  I first noticed the effect when an ammeter
in the primary showed a sudden jump in current as I increased
the primary voltage.
	I don't think you have to "match" the capacitance to
the transformer, but certainly there are resonance effects
which can cause a significant voltage rise, and too large a
capacitance will result in a reduced output voltage.
Ed Phillips