This calculator allows estimation of core loss for a ferrite cored RF transformer using measurements or estimates of magnetising impedance.
There are two elements that are critical to efficient near ideal impedance transformation over a wide frequency range, low flux leakage and sufficiently high magnetising impedance. This calculator helps evaluate the magnetising loss of a configuration, but while low magnetising loss is necessary for efficiency, it does not guarantee sufficiently high magnetising impedance for near ideal impedance transformation.
It provides a useful first analysis of the magnetising impedance (or elements of it) of an electrically short primary winding to infer the approximate core loss of the matched transformer. Matching is performed on the load side of the primary, ie secondary turns and attached load. The input data is typically frequency dependent, so the results only apply at the relevant frequency.
Magnetising impedance can be estimated using one of the following calculators, but keep in mind that there are quite wide tolerances on ferrite cores.
Magnetising impedance can be measured (eg with an analyser), but it should be measured with only the measured winding on the core. Did I mention the wide tolerance of ferrites?
This calculator assumes that the winding is electrically very short and is not significantly affected by self resonance.
The calculator allow input of either magnetising (Rs,Xs), Rp, or G for convenience, use whatever is available from your analyser or design tool. Ro or Go allow specification of the matched input impedance or admittance.
The results are valid only for linear circuits.
The calculator does not do a lot of error checking, if you enter nonsense, it will probably produce nonsense.
© Copyright: Owen Duffy 1995, 2021. All rights reserved. Disclaimer.