In this topic:
Uxxxx n1 n2 model_name [IC=initial_condition] [USEIC=use_ic]
n1 | node 1 |
n2 | node 2 |
initial_condition | Initial condition in Amps. Only active if USEIC is non-zero |
use_ic | If non-zero, enable initial condition. This will set the current in the inductor to the value of initial_condition during the DC operating point analysis |
.MODEL model_name TABLE_INDUCTOR parameters
Name | Description | Units | Default |
L | Inductance | 1m | H |
LTABLE | Saturation table | n/a | |
ITABLE | Current table | A | n/a |
TABLE_SIZE | Number of elements in tables | 2 | |
RSERIES | Series resistance | ???MATH???\Omega???MATH??? | 0.0 |
RSHUNT | Shunt resistance | ???MATH???\Omega???MATH??? | 0.0 (sets to INF) |
LMIN | Minimum inductance | H | 0.0 |
SMOOTH | Smoothing option (0-3) | 0 |
.MODEL TABLE_IND table_inductor L=1 USEIC=0 IC=0 + RSERIES=0 RSHUNT=0 SMOOTH=2 TABLE_SIZE=7 + ITABLE=[0, 8.3333, 16.666, 25, 33.3333, 41.666, 50] + LTABLE=[3.36e-07, 3.36e-07, 3.34e-07, 3.27e-07, 3.09e-07, 1.86e-07, 4.21e-08]
The above example has an inductance of 3.36e-07H at 0A falling to 4.21e-08 at 50A.
The inductance for this device is defined by a lookup table over a specific range. However, the behaviour at currents beyond that defined in the table must also be defined. We refer to the inductance as the 'boundary inductance'. This follows a characteristic of the form:
\[ A/(C+i^{2})+LMIN/L \]
Where ???MATH???A???MATH??? and ???MATH???C???MATH??? are chosen so that the absolute inductance and ???MATH???\frac{dL}{di}???MATH??? matches the table function at the final point.
SMOOTH value | Function |
0 | No smoothing function is selected. Inductor follows a PWL (piece-wise-linear) characteristic |
1 | Local cubic. Fits a cubic polynomial between each pair of points such that the gradient at each point is the average of the slope on either side of the point. This is continuous in the first derivative but is not continuous in the second derivative |
2 | Cubic spline with boundary conditions: lower: ???MATH???\frac{dL}{di}=0???MATH??? upper: ???MATH???\frac{d^{2}L}{di^{2}} = 0???MATH??? |
3 | Cubic spline with boundary conditions: lower: ???MATH???\frac{dL}{di}=0???MATH??? upper: ???MATH???\frac{dL}{di}= \text{slope_of_final_segment}???MATH??? |
SMOOTH=2 and SMOOTH=3 select a cubic spline function. A cubic spline fits a series of cubic polynomials through all points such that the function is continuous in the first and second derivatives. Cubic splines generally require boundary conditions to be set; that is some condition to define the first and last points. This is the only difference between SMOOTH=2 and SMOOTH=3. SMOOTH=2 usually gives the best results but can, in some situations, result in a positive slope at the join with the boundary inductance function. This cannot be matched to the boundary inductance and in these circumstances the device will fail with the error message:
***ERROR*** instance <ref>: Cannot fit spline to table using SMOOTH=2 strategy. Try using SMOOTH=1 or SMOOTH=3
In this case SMOOTH=1 or SMOOTH=3 can be selected.
◄ Inductor (Saturable) | Insulated Gate Bipolar Transistor ▶ |