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Physical Transformer: XFMRP



XFMRP implements a linear model of a physical transformer. This model accounts for core and winding resistive losses as well as parasitic winding capacitances.



Name Description Unit Type Default
ID ID Text X1
N Turns ratio Secondary:Primary   1
Lm Magnetizing inductance Inductance 300 nH
Rc Core loss resistance Resistance 1000 Ohm
k Coupling coefficient   0.9
Rp Primary loss resistance Resistance 10 Ohm
Rs Secondary loss resistance Resistance 10 Ohm
Cp Primary capacitance Capacitance 30 pF
Cs Secondary capacitance Capacitance 30 pF
Ci Interwinding capacitance Capacitance 10 pF

Parameter Details

N. The ratio of secondary to primary turns.

Lm. Magnetizing inductance of primary winding is defined as a product of primary open-circuit inductance Lp and coupling coefficient k: Lm= Lp*k.

Lm(1/k-1), Rs/(N*N), - See "Topology". Series inductances in a T-circuit are leakage inductances. Series resistance in the right shoulder of a T-circuit is equivalent resistance of secondary winding. See [1] for transformer equivalent circuit details.

Implementation Details

Implements physical transformer with primary coil between nodes 1 and 2 and secondary coil between nodes 3 and 4. An equivalent circuit of XMRFP is implemented after [1] with resistive losses and parasitic capacitances added. XMRFP incorporates an ideal transformer model (XFMR), so similar to XFMR DC, it is also transformed with this element. If you do not want to transform DC, you need to add capacitors on either side of the model to block DC.


This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.


[1] E. Brenner, M. Javid, Analysis of Electric Circuits, 2nd ed.: McGraw-Hill Book Company, New York, 1967, Ch. 15.

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