Re: Energy stored in primary again

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

On the subject of inductive storage
isn't this relevant  both to "buzzer-testing" of TCs
and to "kicker-coils"
where in both instances the spark gap is replaced by buzzer contacts
and the high voltage power transformer by an iron-cored choke?

Has anyone tried using a blocking oscillator or similar to replace the
electromechanical switch
for a truly electronic kicker-coil?

Also, aren't the above devices examples of "real" Tesla coils rather than
simple
induction coils?

Jolyon

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, March 08, 2003 8:10 PM
Subject: Re: Energy stored in primary again


 > Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
 >
 > Tesla list wrote:
 >  >
 >  > Original poster: "Jolyon Vater Cox by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >  >
 >  > Dear List,
 >  > I have been thinking about the "energy stored in primary" concept
again. I
 >  > was wondering if the switch SW1 could withstand the high emf induced in
the
 >  > primary when SW1 opened there would be no need for the capacitor C1 to
tune
 >  > the primary OR the quenching switch SW2 to turn off the primary
circulating
 >  > current after predetermined period.
 >
 > The voltage over the switch would be limited only by parasitic
 > capacitances if C1 is not included, and the transformer has a coupling
 > coefficient smaller than exactly 1. Or, you always have C1, and so it's
 > better to use the right value. In classical induction coils, without
 > C1 the mechanical switch produces an intense spark that dissipates most
 > of the primary energy when opening. An electronic switch would be very
 > surely destroyed in little time. About the quenching switch, would it
 > really make some difference if the primary has low losses? Remember that
 > there is no spark gap in this configuration.
 >
 >  > This is my reasoning: with the tesla coil T1 viewed as an ideal
transformer
 >  > the secondary voltage is referred back to the primary by the turns
ratio;
 >
 > Ok.
 >
 >  > now T1 isn't an ideal transformer as not all the magnetic flux from the
 >  > primary is coupled to the secondary i.e. there is a "leakage" component
 >  > inherent in the primary inductance which can be visualised as an
inductor
 >  > in series with the primary of the hypothetical ideal transformer.
 >
 > Ok too. K<1, high-frequency approximation.
 >
 >  > the leakage reactance will be series-resonant with secondary
capacitance C2
 >  > over the turns ratio of the ideal transformer after SW1 is opened
 >  >
 >  > Thus SW1 will "see" a voltage across its terminals
 >  > not equal to the power rail voltage
 >  > but to the voltage across the "transformed" C2 resonating with the
leakage
 >  > reactance.
 >  >
 >  > Is my reasoning correct?
 >
 > Not exactly. The problem is that the interruption of the current in the
 > leakage inductance, without C1 across the switch, produces a voltage
 > impulse (an infinitely large pulse with infinitely small duration, but
 > nonzero area) over the switch. A fraction of the initial energy
 > disappears instantaneously, before the start of the oscillations. In
 > practice, a parasitic C1 will limit the amplitude (in a huge value)
 > of the pulse and stretch it in time. A high-amplitude, high-frequency
 > oscillation will appear over the switch. You are trying to interrupt the
 > current in an inductor, and this always produces a voltage L di/dt
 > over it.
 >
 > Antonio Carlos M. de Queiroz
 >
 >
 >