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Re: [TCML] SISG Technology

Hi Jim,

Commonly available thyristors would perform poorly as the high current switching elements in a TC primary circuit. Unless specially fabricated for pulsed power use, they'll turn on too slowly (i.e., specifically the di/dt spec). This may progressively or immediately destroy the thyristor as excessive current flows through a small conducting region before the rest of the device can turn on. This problem occurs via normal gate triggering, by forced turn-on through device overvolting, or via rapid voltage changes (dv/dt) across an "off" device. All can occur within a Tesla Coil primary circuit. Using small HV thyristors (i.e., SIDAC's) to trigger readily available IGBT's is a more cost-effective approach, and is scalable to a wide variety of high current IGBT's. Indirect optical trigger control through fiber is already used on many DRSTTC's.


Jim Mora wrote:
Hello Bert, et al,

I wonder if anyone on the list has experimented with this approach. My first
impression is that component costs would be higher? Triggering with fiber is

Jim Mora

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Bert Hickman
Sent: Thursday, February 05, 2009 6:54 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] SISG Technology

Hi Bart,

Nope - this guy didn't abscond with Terry's SISG design...

This particular patent (dated 2002) predates Terry's SISG work by about 4 years and, unlike Terry's approach it uses stacked high speed thyristors as the main current carrying element, with optical sensor/IGBT or pulse transformer triggering for each stage. The SISG is kind of the reverse of this - it uses a thyristor to trigger IGBT power switches. This proposal appears to be a pulsed power adaption of similar optically or transformer isolated stacked thyristor circuits used for the inverters in HVDC electrical power transmission systems. Specially fabricated high di/dt thyristors were employed in this application for faster turn on time. As with the SISG, diodes are used to conduct reverse pulse current. You can see the full disclosure of the approach, schematics, and test results here:


HOWEVER: I see no reason why stacked SISG-like circuits could not be used for certain pulsed power applications, and it would not surprise me to see SISG-like circuits applied to this arena...


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