DCR of a DRSSTC primary circuit

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

Hey guys,

I performed a test today to find the DCR of my DRSSTC-1.

The test goes as follows.  Run the coil with no secondary, keep the
voltage low, and use a long enough pulse length to get past the
transient condition.  Measure the current with the fancy pearson CT i
borrowed, measure the V, so now i know the DC resistance of the whole
circuit.  I found the DCR to be about .1 ohms.  This was tested with
11VDC rail voltage, 1mS pulse lengths (at just a few hz) and the
current was 80A.  Now im *assuming* with a 28V gate drive that the Vce
of the IGBTs should be about 1.5V or so.  This gives 8V/80A or .1ohms.

I have been using .1 ohms in my spice simulations all along since it
gave the most realistic primary currents.  So unfortunately this wasnt
a "breakthrough" but it does give me more confidence in my model.
BTW, pspice says i should get about 90A with a solid 8VDC input, but
pspice doesnt have the supply sagging like i do.  This sagging gives
some uncertainty to my measurements.. during the burst my voltage
might really be 10V or 9.5V.  That would make the DCR even lower,
though.  So i think .1 ohms should be close enough for modeling work.

Comments and questions are welcome.  Please point out if i missed
anything obvious in my test.

Steve