Re: Series Connection of IGBT / MOSFET Switches - SSSG

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

Original poster: "David Sharpe by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>

Jan

Several issues with GTO's (Gate Turn Off Thyristors):

1.  You want to be able to gate the device on, then let circuit ring down 
to '0'.
      A GTO is the electronic dual of an SCR, i.e. it is always on with 
positive
      bias anode >> cathode current until you gate it OFF.  Gate signals are
      generally 20% of cathode current with a negative polarity.  GTO's are
      available in very high voltage's (at least 9kV for a single 
device).  Also
      very slow compared to a IGBT (more akin to a SCR or IGCT), upper
      end Fo of 5-10KHz.
2.  Gate drive circuits for GTO's are _significantly_ more complex then
      those for an SCR, or even IGBT's with overcurrent protection.  I've
      marveled at the complexity of medium voltage GTO drives gate circuitry
      compared to IGBT or newer IGCT drives.  GTO's were used because
      they were the only device that could play the game at medium voltages
      in the mid 1980's to recently.  Now IGCT's and more so IGBT's are
      succesfully competing, primarily because of improved simplified gating
      controls, better long term reliability, and higher voltage/power devices
      becoming commercially available.
3.  The GTO has been largely obsoleted and replaced by the newer IGCT
      or GCT family of devices, where a positive pulse turns device on and a
      negative pulse turns device off.

I see the sun setting on GTO technology except perhaps in really high power
(AC-DC power transmission), or where fast disconnection of load from power
is a requirement as a solid-state circuit breaker.

Regards
Dave Sharpe, TCBOR
Chestefield, VA USA

Tesla list wrote:

 > Original poster: "Jan Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<jwagner-at-cc.hut.fi>
 >
 > Hi,
 >
 >  > As a sidebar from the Chicago Power Electronics Conference,
 >  > I found this URL for an App. Note from IXYS concerning
 >  > applying IGBT's or MOSFET's in series for capacitive discharge
 >  > (OLTC) applications.
 >  >
 >  >   http://www.ixys-dot-com/t080698a.pdf
 >
 > Just curious, why isn't anyone considering GTO thyristors for this?
 > ok they do eat a lot of gate current, and switching time is around 10us
 > or longer, but, for "spark gap" replacement it should work very well. I
 > mean, something like 4kV 3kA-continuous is possible. GTOs being older tech
 > than igbts they should be comparatively cheap to get...
 >
 > cheers,
 >   - Jan
 >
 > --
 > *************************************************
 >   high voltage at http://www.hut.fi/~jwagner/tesla
 >   Jan OH2GHR