Re: DCR of a DRSSTC primary circuit

["Tesla list" <tesla@xxxxxxxxxx>]

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

Gerry,

That resistance is measuring EVERYTHING, that is, the ESR of the MMC,
any connections, the whole circuit.  Note that i did have to adjust my
apparent voltage to accomodate the 1.5V drop per IGBT (so i subtract
3V from the VDC that i measure on the buss caps).  The current i
meausure with the CT is the real current through the primary circuit.

This does not measure the ESR of the electrolytic capacitors, since im
measureing the VDC at the terminals of the caps, so the VDC is after
the ESR of the lytics.

Steve

On 6/22/05, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Steve,
>
> Is the 0.1 ohms is for just the primary coil??  I normally take a current
> limited PS and put say 1amp thru the low resistance and measure the mv of
> Vdc across the low resistance.  To this resistance, do you add the ERS of
> the caps and figure the source resistance of the IGBT's???
>
> Gerry R.
>
> >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
> >
> >
>
>
>
>
>