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Re: [TCML] MOT Measurements
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
bartb skrev:
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,
Bart
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