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Add Lundin's geometry correction to the 

inductance formula
This commit is contained in:
Holger Vogt 2022-06-22 12:59:37 +02:00
parent 4a96691b49
commit 79ef586fef
1 changed files with 45 additions and 2 deletions
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47
src/spicelib/devices/ind/indsetup.c
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@ -10,6 +10,10 @@ Author: 1985 Thomas L. Quarles
#include "ngspice/sperror.h" #include "ngspice/sperror.h"
#include "ngspice/suffix.h" #include "ngspice/suffix.h"
#define PI 3.141592654
static double Lundin(double l, double csec);
int int
INDsetup(SMPmatrix *matrix, GENmodel *inModel, CKTcircuit *ckt, int *states) INDsetup(SMPmatrix *matrix, GENmodel *inModel, CKTcircuit *ckt, int *states)
/* load the inductor structure with those pointers needed later /* load the inductor structure with those pointers needed later
@ -56,8 +60,18 @@ INDsetup(SMPmatrix *matrix, GENmodel *inModel, CKTcircuit *ckt, int *states)
* model->INDcsect) / model->INDlength; * model->INDcsect) / model->INDlength;
} else { } else {
model->INDspecInd = 0.0; model->INDspecInd = 0.0;
} }
/* Lundin's geometry correction factor */
model->INDspecInd *= Lundin(model->INDlength, model->INDcsect);
/*
double kl = Lundin(model->INDlength, model->INDcsect);
double Dl = model->INDlength / sqrt(model->INDcsect / PI) / 2.;
fprintf(stdout, "Lundin's correction factor %f at l/D %f\n", kl, Dl);
*/
/* How many turns ? */
if (!model->INDmIndGiven) if (!model->INDmIndGiven)
model->INDmInd = model->INDmodNt * model->INDmodNt * model->INDspecInd; model->INDmInd = model->INDmodNt * model->INDmodNt * model->INDspecInd;
@ -118,3 +132,32 @@ INDunsetup(GENmodel *inModel, CKTcircuit *ckt)
} }
return OK; return OK;
} }
/* Calculates Nagaoka's coeff. using Lundin's handbook formula.
D: W. Knight, https://g3ynh.info/zdocs/magnetics/Solenoids.pdf, p. 36 */
static double Lundin(double l, double csec)
{
/* x = solenoid diam. / length */
double num, den, kk, x, xx, xxxx;
if (csec < 1e-12 || l < 1e-6)
return 1;
x = sqrt(csec / PI) * 2. / l;
xx = x * x;
xxxx = xx * xx;
if (x < 1) {
num = 1 + 0.383901 * xx + 0.017108 * xxxx;
den = 1 + 0.258952 * xx;
return num / den - 4 * x / (3 * PI);
}
else {
num = (log(4 * x) - 0.5) * (1 + 0.383901 / xx + 0.017108 / xxxx);
den = 1 + 0.258952 / xx;
kk = 0.093842 / xx + 0.002029 / xxxx - 0.000801 / (xx * xxxx);
return 2 * (num / den + kk) / (PI * x);
}
}