KXXXXXXX L1...LN <K> <MODEL NAME> <SIZE> <LM> <A> <LG> <G> <B0>
Non-Linear Coupled (Core) Inductor Instance Parameters-
| Name | Meaning | Units | Default |
| L1...LN | Inductor names | - | - |
| K | Coupling value | - | 1.0 |
| SIZE | Scaling factor | - | 1.0 |
| LM | Magnetic length | meters | 0.01 |
| A | Cross-sectional area | sq meters | 0.0001 |
| LG | Air gap | meters | 0.0 |
| G | Window height | meters | 0.125*LM |
| B0 | Initial flux | Gauss | 0.0 |
In the following .MODEL statement example, core1 is the model name, and tfm is the model type:
.model core1 tfm bs=2.0 br=1.0 hc=1.0
The following table lists the core model parameters used in this statement, as well as parameters used in the test circuit that follows.
Non-Linear Coupled (Core) Inductor Model Parameters
| Name | Meaning | Units | Default |
| BS | Saturation flux | Gauss | 2.0 |
| BR | Remnant flux | Gauss | 1.0 |
| HC | Coercive force | Oersted | 1.0 |
| TBS | Temperature coefficent | °C-1 | 0.0 |
| TBR | Temperature coefficent | °C-1 | 0.0 |
| THC | Temperature coefficent | °C-1 | 0.0 |
Most Core manufacturers provide BS, BR and HC directly. For those manufacturers who do not, BS, BR and HC can be derived from the major hysteresis loop of a B versus H curve as show in the following plot.
HC is measured where the major hysteresis loop crosses the B = 0 axis. BS is measured as the maximum Flux Density (B). BR is measured where the major hysteresis loop crosses the H = 0 axis.
An Example of a B versus H Major Hysteresis Loop
Temperature Coefficient Equations
The following equations show how TBS, TBR, and THC are used in the Core model:
BR(T) = BR (1 + (T - Tnom) TBS) BR(T) = BR (1 + (T - Tnom) TBR) HC(T) = HC (1 + (T - Tnom) THC)
The following test circuit shows hot to use the core inductor parameters listed in Table 4-14:
** TRANSFORMER MODEL TEST * . MODEL TMOD TFM BS=2.0 BR=1.0 HC=1.0 FC1=1.0 FC2=0.0 ITEST N001 0 DC 6 SIN(0 6 1k 0 400) RTEST N001 1 1 VTEST 1 2 DC 0 AC 0 0 LTEST 2 0 2 LTEST2 2nd 0 1 RTEST2 2nd 0 1 KTEST LTEST LTEST2 1.0 TMOD LM=1 A=1U LG=0 .OP .TRAN 10US 10.0MS 0 10US .OPTIONS ACCT NODE LIST .PRINT TRAN V(2) V(2nd) .PRINT TRAN I(VTEST) .PROBE/CSDF .END
As an example, the test circuit from this Chan[1] paper shows how to use the core inductor parameters.
Transformer test circuit from Chan paper:
.model core1 tfm bs=2 br=1 hc=1 tbs=0 tbr=0 thc=0 ia 0 1 sin(0 6 1e3 0 400) va 1 2 0 la 2 0 1 ka la core1 lm=1 a=1 lg=0 .tran 0.01m 10m 0 10U .probe/csdf .end