Next: , Previous: Inductors, Up: Elementary Devices


8.2.8 Inductor model

The inductor model contains physical and geometrical information that may be used to compute the inductance of some common topologies like solenoids and toroids, wound in air or other material with constant magnetic permeability.

name parameter units default example
IND model inductance H 0.0 1e-3
CSECT Cross section meters^2 0.0 1e-3
LENGTH Length meters 0.0 1e-2
TC1 first order temperature coeff. F/^oC 0.0 0.001
TC2 second order temperature coeff. F/^oC^2 0.0 0.0001
TNOM parameter measurement temperature ^oC 27 50
NT number of turns - 0.0 10
MU relative magnetic permeability H/meters 0.0 -

The inductor has an inductance computed as:

If value is specified on the instance line then

                        Lnom = value * scale / m

If model inductance is specified then

                        Lnom = IND * scale / m

If neither value nor IND are specified, then geometrical and physical parameters are take into account. In the following formulas NT refers to both instance and model parameter (instance parameter overrides model parameter):

If LENGTH is not zero:

                                   2
                       MU * mu * NT * CSECT
     			 0
                Lnom = --------------------   if MU is specified
                             LENGTH
     
     
                              2
                       mu * NT * CSECT
                         0
                Lnom = ---------------   if MU is not specified
     		      LENGTH
     
     with:
     
     mu =  1.25663706143592e-6  H/m
       0
     

After the nominal inductance is calculated, it is adjusted for temperature by the formula:

                                                          2
       L(T) = L(TNOM) [1 + TC  (T - TNOM) + TC  (T - TNOM) ]
                             1                2
       where L(TNOM) = Lnom

In the above formula, `T' represents the instance temperature, which can be explicitly using the temp keyword or calculated using the circuit temperature and dtemp, if present.