CIRCUIT ANALYSIS USING SPICE AND PSPICE
MUTUAL INDUCTANCE AND TRANSFORMERS
The mutual inductance between inductors is modeled by a device whose name begins with K. The data statement syntax is hnamei
The dot rule, which determines the sign of the mutual inductance term, is observed by making the dotted end of each inductor the ﬁrst node entered in its data statement. EXAMPLE 15.15
Write the three data statements which describe the coupled coils of Fig. 15-15.
Fig. 15-15 pﬃﬃﬃﬃﬃﬃﬃﬃ The coupling coeﬃcient is k12 ¼ 1:5= 2ð3Þ ¼ 0:61. The netlist contains the following: L1 L2 K12
1 3 L1
2 4 L2
2 3 0.61
EXAMPLE 15.16 Plot the input impedance Zin ¼ V1 =I1 in the circuit of Fig. 15-16(a) for f varying from 0.01 to 1 Hz. To ﬁnd Zin , we connect a 1-A ac current source running from node 0 to node 1 and plot the magnitude and phase of the voltage V(1) across it. The source ﬁle is AC analysis of coupled coils, Fig. 15-16 IADD 0 1 AC 1 C 0 1 1 000 000 uF R 0 2 3 L1 1 2 2H L2 3 2 5H K12 L1 L2 0.6325 H L3 0 3 1H .AC LIN 20 .01 1 .PRINT AC Vm(1) Vp(1) .PROBE .END
Vm(1) and Vp(1), which are the magnitude and phase of Zin , are plotted by using Probe and the graph is shown in Fig. 15-16(b). Note that the maximum occurs at about 100 mHz.
MODELING DEVICES WITH VARYING PARAMETERS
.MODEL Statement The parameters of a passive element can be varied by using .MODEL statement. The syntax is :MODEL
where hnamei is the name assigned to the element.
½ðhparameteri ¼ hvalueiÞ For passive linear elements, htypei is
RES for resistor IND for inductor CAP for capacitor