Re: [TCML] MOT Measurements

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Ted -

An update: I mentioned I drove 700V and measured 185A using your method. 
The 132A primary current I mentioned was a 120V input and really I 
should have inserted 40V at the source which is the equivalent L1 volts 
(57A at that point). I also measured the open circuit current at 16.1mA. 
For my MOT, 700V at L2 is 38.9V at L1 and coupling is 0.976 (measured 
and why it's helpful to log this data down in 10V increments for future 
reference).

For this open circuit current of 16.1mA, L2 is 115H and L1 is 356mH. I 
set the transformer model to these L and k values and set the source 
voltage to 40V. For a shorted secondary, primary current was measured at 
6.62A with 40.2V input. The simulation showed 6.45A (once again in good 
agreement using "open circuit" current measurements finding the 
inductances with those values). Again, with your method, the simulation 
showed 57A at the primary, which of course not correct.

I just wanted to show that the secondary side can be driven just like 
the primary side to extract the L's (but open circuit measurement is 
necessary for extracting the L's). It's much easier however to just 
drive the low voltage side and much easier to control. You will get the 
same inductances when simply driving L1 as you would by driving L2 at 
the equivalent voltages.

Short circuit testing is necessary for finding various parameters 
(coupling, magnetizing currents, power curves, core and Cu losses, 
etc.), but not very helpful for inductances.

Take care,
Bart

bartb wrote:
> I tried your method and applied 700V to L2 and measured 185mA. Thus, 
> Z=3784, L2=10H, L1=32.8mH. I ran the same test again as above and the 
> simulation then showed 132A primary current, which is very wrong. 
> According the simulator, these inductances are not correct even with 
> large coupling changes.
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