Transformer model question

[Jayber]

I have a transformer that I'm trying to model. The frequency is in the hundreds of khz. I'm using an HP impedance analyzer to measure inductances. I'm using the following model.

In the model, is Lp the measured inductance across the primary when the secondary is open? Or is that L_sigma_p? I dont' understand which variable is the actual measurement.

 

[D.A.(Tony)Stewart]

The effective measured primary impedance is a function the Lp, Ls,Lm , Rp, Rs and turns ratio a as shown in the formulae. In addition, the load impedance transformed to the primary side would be included , as Rs might be meaningless without a load.

This model might be inaccurate for you as it neglects the inter-winding capacitance, the core nonlinearity and the coupling capacitance between primary and secondary.

 

[Jayber]

I've added the capacitances but they do not make that big of a deal. Can someone explain how to measure/calculate the series inductors in the model.

Lp=?
Ls=?

I think I know how to measure everything else.
a = V_primary/V_secondary
M = (la-lo)/4
where la = inductance of windings in series
lo = inductance of windings in series in reverse

 

[chuckey]

If put a short circuit on the secondary, you will measure the primary leakage inductance plus the reflected secondary leakage inductance. if you then short the primary and measure the secondary, you get the secondary leakage inductance plus the reflected primary leakage inductance. I would think that mathematically you can sort out the actual leakages.
Frank

 

[D.A.(Tony)Stewart]

It would help to define your Core and dielectric type , power rating and if intended as a Voltage transformer or Instrument Transformer or for impedance matching?

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The reason I ask is a 50 Ohm Impedance Analyzer is not the proper method of testing ANY transformer other than 50 Ohms transformers. Are you seeing the effect of L/R ratio?


if not a 50 ohm type, there are other test methods.

 

[The Electrician]

I have a transformer that I'm trying to model. The frequency is in the hundreds of khz. I'm using an HP impedance analyzer to measure inductances.

Which model HP impedance analyzer are you using?