>Jim, do you have data for the winding resistance of the 5300V transformers?
>73, Mike W4EF....................
You could have identical secondary resistances but different primary
resistances.....and end up with different secondary voltages.
Watch out when trying to measure primary DC resistance.
On my big 253 lb dahl I was measuring .5 ohm DCR on the primary.....and
6.0 ohms across the 5200 vac secondary.
Was getting screwy results using PSUD-2 software. Duncan Munro ( who
runs the PSUD-2 site) told me that you can't use a fluke DVM or any DVM
to measure the primary DCR of xfmrs that have a low DCR on their primary.
Correct method is to use a DC lab supply and apply DCV to the primary (
sec can be open or shorted, no difference) and simply divide the applied
DCV / DC current to calculate the real pri DCR.
I have 3 x lab supplies. With .9 vdc applied, it sucks 7.83 amps. .9
vdc / 7.83 amps = .115 ohms of DCR.
Ok, plug .115 ohms into the PSUD-2 software ( along with the 6.0 ohms
sec DCR) and bingo, all the numbers come out correct. The correct pri
and sec DCR is used to calculate the Source Z in his software..... used
for everything.
I also tried using the lab supply on the sec, but got the same 6.0 ohms as
just using my fluke 87.
IE: 6 v and 1 amp = 6 ohms. Also tried 12 vdc and 2 amps = 6 ohms. And
also 18 vdc and 3 amps = 6 ohms.
On a similar note, My B+K 875B digital LCR meter can not be used on the
pri or sec. Reason is, unlike my B+K 875 which reads DCR..... my new
B+K 875B reads AC resistance and uses a 1 khz square wave on the test
leads. U can't stuff a 1 khz square wave into a pri or sec of a plate
xfmr..... it blanks out.
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