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Re: SISG IGBT power loss calculations

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

Hi Terry,

Neat stuff, so the resistance is lower than you first thought. You better order some more boards cause there will be a demand for them :-))

We will need to try this on a 21KV SISG string.

Gerry R.

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

I have been matching figures 10 and 11 in the SISG pdf:


to models. It appears that the very low resistance allows the inductance of the SISG gap to become significant and thus is why voltage and current are out of phase. It is neat because that gives the resistance a poorer power factor which makes it run cooler :-))

The gap appears to be a 0.020 ohm resistor in series with a 20nH inductor. So for power calculations, each gap section dissipates the primary loop RMS current squared multiplied by 0.020 ohms.




For my 183 watt test, the RMS primary current is 11 amps, so the power in the five sections is 12 watts total.

Thus, the gap is loosing about 6.6% of the total coil energy. The only other major loss would be in my big secondary made from #28 wire that probably dissipates 8 watts as heat. So with 183 watts in, about 163 watts is making it to the streamer for an efficiency of 89%. That would actually place an upper limit on the Freau value of 2.35. To get there (or real close) one needs to reduce the RMS current and make the secondary reasonably low loss. Lots of tradeoffs to juggle there...