Re: Parallel resonant DRSSTC

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>

Hi Sue,

Solid state switches tend to be low impedance so in a parallel system there
would large switching surge currents due to the parallel C.  This can be
overcome by inserting L in the DC  line but that means hard switching. There
may be other ways round that too.
Assuming any method results in an high impedance source then parallel L C is
equivalent to the series one with a low impedance switch. Assuming which
ever you pick is correctly matched to the secondary.

So assuming the switching surges can be solved the difference are:
Parallel:  large circulating currents so low L high C.
Series: large voltages on the L and C so high L low C.

Which is more practical?   .

An other way of looking at it is to note that a parallel L C is low
impedance at all frequencies other than resonance.
So if you apply a square wave from a low impedance to it the harmonic
currents are huge because it effectively a sort circuit.

Where as a series L C is an open circuit at all frequencies except at
resonance so only the resonance frequency passes thru.

It gets more complicated when you consider the start up of a train of square
waves i.e. transient conditions but the switching surges remain a problem.

Note that as a tube is almost a constant current source you can use a
parallel L C with out the surge problem.

To address your particular question about almost no current thru the
switched. That's not true.  The current thru the switches is determined by
the power you decide to pump in to the system by selecting the primary
turns, operating frequency and mode etc.


Bob

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, January 06, 2005 10:27 AM
Subject: Parallel resonant DRSSTC


> Original poster: Sue Gaeta <sgsparky@xxxxxxxxxxx>
>
> Hi all,
>
> I was curious if anyone has ever tried designing a DRSSTC using a
capacitor
> in parallel with the primary rather than in series with it. If something
> like that could work it would have a big advantage that the extreamly high
> primary current would be between the capacitor and primary, and there
would
> be almost no current throgh the switching devices.
>
> Has anyone ever thought of something like this, or played with the idea
> with simulation software?
>
> What would be the disadvantage of something like that?
>
> Sue
>
>
>