[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

SISG equivilent of SRSG

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Terry and all,

A little thinking out loud..... (and hopefully, a little collective brainstorming). It seems like the SISG is a great replacement for static sparkgaps cause of the reduction in losses (and noise). Currently, the SISG circuit is unipolarized requires a DC supply for charging. Im wondering how this will compare to the SRSG (an AC device) since firing after peak can allow full charging of almost twice the capacitance that an AC power source can charge with a static gap. Taking the SISG one step further, Im thinking that it may be possible to use the SISG concept in an AC application (no HV rectifying required) to trigger a circuit that determines a delay so firing will occur after peak.

One possible implementation would be to use a common circuit that detects peak voltage of the charging sine wave and initiates a delayed trigger for a series string of IGBTs. This circuit would need to detect both positive and negative peaks so a trigger control signal can be generated for both directions. The control signal would then need to control a series of IGBT's, each at a different ON/OFF potential within the string. An optical control signal comes to mind to allow for the needed isolation. A three terminal (two power terminals and an optical control terminal) module could be built, each containing two IGBTs (one for positive switching and one for negative switching), resister equalizer across the IGBT pair, and a converter to allow the optical control input to determine the gate voltage. The IGBT would need to NOT have the "reverse" diode so the switch can be turned off in both directions (hopefully this part exist). If a suitable part exists similar to a FET where current can flow in both directions, then maybe the two IGBTs can be replaced with a single part. It would be perfect if there was such a FET like device that directly had an optically controlled gate (I'm just not up on high power analog devices). If not, it would be desirable to have the gate control circuit be low power and use the optical energy to generate the gate voltage. If the converter needed some electrical power, one could extract it from the voltage difference between the two power terminals when the switch is OFF.

Any comments or suggestions welcomed.

Gerry R.