Coupled Inductors Model

Model Kind

General

Model Sub-Kind

Coupled Inductors

SPICE Prefix

K

SPICE Netlist Template Format

LA_@DESIGNATOR %1 %2 @"INDUCTANCE A"
LB_@DESIGNATOR %3 %4 @"INDUCTANCE B"
@DESIGNATOR LA_@DESIGNATOR LB_@DESIGNATOR @"COUPLING FACTOR"

Parameters (definable at component level)

The following component-level parameters are definable for this model type and are listed on the Parameters tab of the Sim Model dialog. To access this dialog, simply double-click on the entry for the simulation model link in the Models region of the Component Properties dialog.

Examples

Consider the transformer in the image above, which uses a coupled inductor model and has the following characteristics:

• The positive pin of the Primary is connected to net Vin2
• The negative pin of the Primary is connected to net GND
• The positive pin of the secondary is connected to net Vout2
• The negative pin of the secondary is connected to net GND
• Designator is T1
• Inductance A = 1mH
• Inductance B = 1mH
• Coupling Factor = 0.5

The entry in the SPICE netlist would be:

LA_KT1 VIN2 0 1mH
LB_KT1 VOUT2 0 1mH
KT1 LA_KT1 LB_KT1 0.5

Placing a transformer with a coupled inductor model is probably the simplest and quickest way of adding a coupled inductor to your source schematic. However, should you wish to place individual inductors in the schematic design and couple them, the required information for the SPICE netlist can be readily supplied through the use of a Text Frame. Simply place a text frame in the schematic document and ensure that the first line is:

.NSX

Then type the information required. Each line will be included in the netlist, exactly as it is written, appearing between the following comment entries:

*Begin NSX text frames
*End of NSX text frames

The following example illustrates the use of two inductors and a text frame to provide a coupled inductor for simulation purposes.

Consider the circuit in the image above, which contains two discrete inductors with the following characteristics:

• Designator (Primary inductor) = L1
• Designator (Secondary inductor) = L2
• The positive pin of L1 is connected to net Vin1
• The negative pin of L1 is connected to net GND
• The positive pin of L2 is connected to net Vout1
• The negative pin of L2 is connected to net GND
• Value for inductance (L1) = 10mH
• Value for inductance (L2) = 10mH

The entries in the text frame are dissected as follows:

• .NSX - the mandatory first line that tells the netlister that the following lines are extra information to be added when generating the SPICE netlist.
• K1 - the designator for the 'coupled inductor', where K is the required SPICE prefix.
• L1, L2 - the designators of the two individual inductors
• 0.5 - the value for the Coupling Factor

The entry in the SPICE netlist would be:

*Begin NSX text frames
K1 L1 L2 0.5
*End of NSX text frames
.
.
*Schematic Netlist:
L1 VIN1 0 10mH
L2 VOUT1 0 10mH