[TCML] MOT Measurements
f-h at c.dk
Tue Jan 13 11:28:11 MST 2009
This is getting more and more interesting.
To me, the news is the variation in leakage inductance with input voltage.
Back when I ran simulations with these transformers, I measured the
inductance of the primary, then calculated the secondary inductance and
plugged them in microsim.
After that, I would adjust coupling until the model delivered the same
current into a short, as the real thing did.
Of course, Microsim supplied a leakage inductance that fits in the
process, so resonance at full input voltage wouls be modelled faithfully.
I never interested in the low voltage situation, but maby this explains
why the coils seem to "kick in" when the variac gets turned right up?
Cheers, Finn Hammer
> Hi All,
> I hope I'm not boring you with this (I'm sure some are). But I think
> the next step is to look at a 15/30 NST which has not been modified. I
> have a couple on hand (Franceformers). I have a "gut feeling" that we
> really don't know where shunted transformers (NST's, MOT's, etc.) are
> truly at. Some resonant charging may or may not be occurring with our
> tank cap values. All the programs (including my own Javatc) are
> looking at Cres of non-shunted transformers. The shunted transformer
> is a different beast and without measurements, only guesses.
> These transformers force leakage inductance via the shunts to apply
> regulation. This changes the transformer as we assume it to be as far
> as currents, voltages, Cres, etc. The load also changes the output.
> NST's will begin to suffer a voltage drop even with a small load.
> MOT's are current beasts, and they will require larger loads before
> significant change in output voltage is seen. Load impedance of
> shunted transformers is yet another set of tests that should be
> performed at some point.
> I'll run through my normal 10V increment routine with one of my
> 15/30's. I'll set a variac to as near 10V as I can get, then measure
> the open and short circuit primary currents as well as open secondary
> voltage. Then head up to 20V and do all again. This is my routine as
> it keeps the source voltage unchanging, and thus, the numbers for Ioc,
> Isc, Vin, and Vout are all in very good agreement. My plan is to first
> do this unloaded (basic transformer testing). But loading is yet
> another issue.
> If anyone has any additional thoughts, please let me know. For the
> NST, considering it's low power, I can will also measure true power as
> well as VA.
> Best regards,
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