RE: Series connection of Mosfets/IGBTs

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

Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com> 

 >Series tuned primary, what is that?
 >Is it what Marco uses in his SWmode supply? (Series cap resonating with
 >leakage inductance)
 >Does it make the secondary system invisible to the primary?
 >If it is good, how do we make it?

First of all this is a SSTC thing. Classic coils already have a tuned
primary :)

Just take a normal SSTC, loosen the coupling a bit, and connect a capacitor
in series with the primary, of a value that will resonate with the primary
inductance. The capacitor has to be a kind that will stand a high RF
current, either a "MMC" of pulse caps in parallel, or a ceramic transmitting
type cap.

Now stand well back and throw the switch. The series tuned primary seems to
boost performance quite drastically, but increases the chance of blowing up
your transistors.

A series tuned SSTC (also known as dual resonant or DRSSTC) also has
interesting transient behaviour that lets it generate very high power pulses
in the manner of a clasic coil, but with higher efficiency than a
solid-state "spark gap replacement". Jimmy Hynes did a lot of work on this
and got excellent results, although his setup did have a tendency to
explode, throwing little pieces of IGBT all over the garage.

http://www.hot-streamer-dot-com/chunkyboy86/ iirc

Now that high-speed high-current IGBT modules are getting more common in the
surplus market, I reckon the DRSSTC is the future for solid-state coiling.
The OLTC is a good way of making use of all those old slow IGBTs though :)
besides being a bit easier to build, and arguably less likely to go
KaBlooie.

Steve Conner
Power Electronics Misapplications Dept.
scopeboy-dot-com