Off Line - DRSSTC (OL-DRSSTC) Concept....

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

	The OLTC is very simple and tough, the DRSSTC is fairly complex and 
not quite as tough...  I think there is a system (concept only!) that 
might marry the two in a very simple, cheap, and hardy configuration 
that any coiler should be able to put together...

I direct you attention to this schematic:

http://hot-streamer.com/temp/OL-DRSSTC.gif

Allow me to explain...

From the top right, the AC line voltage (probably from a variac) is 
rectified and charges a capacitor (Cresonant) through a blocking 
inductor to say 300VDC.  This capacitor is similar to the ~3000uF 
buss caps we use in the DRSSTC.  However, this capacitor is 
significantly smaller in value since it is limiting system power in 
this "fixed" 120 BPS coil.  For a 1000W 120 BPS coil:

1000W = 120BPS x Ecap    Ecap = 8.33Joules    8.33 = 1/2 x C x 
300^2   C = 185uF

Note that with the proper selection of blocking inductor, the 
capacitor voltage can be "resonantly doubled" off the 60Hz AC 
line.  I think "my" OLTC is the only one that ever used that proven concept...

Note that if the IGBTs obnoxiously decide to cross conduct, the 8.33 
joules could be absorbed directly by the thermal mass of the IGBTs 
and the blocking inductor would provide time for them to correct. - 
It should never blow up...

So every 120th of a second, the system is provided with a say 185uF 
cap charged to 300VDC to "run the thing"...  The duration of the 
cycle will be determined by how long it takes to use up the 185uF cap's energy.

Lprimary and Cprimary are typical per DRSSTC standards as is the 
secondary coil and all...

The H-bridge has four typical IGBTs with anti-parallel diodes.

The gate drive to the IGBTS is derived directly from the primary 
current now!  There are four current transformers that provide 
isolated gate drive directly to each of the IGBTS from the primary 
current loop.  Back to back Zener and Schottky diodes provide voltage 
control and very fast switching control of the current from the CTs 
to control the IGBTs.  Of course, the "phasing" needs to be correct...

So the 185uF cap will discharge thought the IGBT H-Bridge and drive 
the coil.  The direct connected, but voltage limited, CTs will 
feedback the primary current to the IGBTs providing synchronized 
timing control.

The firing MOVs "start" the cycle.  Once the voltage reaches their 
level, they will conduct and "turn on" the system so the CT and IGBT 
system will start running.

As the 185uF cap drains, the system will fall out of 
conduction.  When the primary current and drive signals collapse, the 
system's power will be almost all drained, so no harm should come...

This is all purely untested "pie in the sky stuff"...  But if the 
concept is valid, it would bring together the best of the OLTC and 
DRSSTC together in a very simple, cheap, and robust system.

You can hold the AC line -  to primary tank drive system in the palm 
of your hand!!!

If the concept holds, everything just changed... Again ;-)))

Cheers,

	Terry