Resistive Circuit Nodal Analysis

Capture and PSpice can be used to easily calculate the Norton and Thevenin equivalents of a circuit. The method we will use is the same as if we were going to find the equivalent circuits in the lab. We will make two measurements, the open circuit voltage and the short circuit current. The Thevenin resistance is then the open circuit voltage divided by the short circuit current. This will require us to create two circuits, one to find the open circuit voltage, and the second to find the short circuit current. In this example, we will find the Norton and Thevenin equivalent circuits for a DC circuit. This same procedure can be used to find the equivalent circuits of an AC circuit (a circuit with capacitors or inductors). However, instead of finding the open circuit voltage and short circuit current using the DC Nodal Analysis, we would need to use the AC analysis. 

The EMTP was based on the Schnyder-Bergeron method [54,55] of traveling-wave analysis in a hydraulic system, well known as a water hammer [52, 53, 54, 55, 56-57]. The Schnyder-Bergeron method was introduced to the field of electrical transients by Frey and Althammer [25]. The method was incorporated with a nodal analysis method by representing all of the circuit elements by a lumped resistance and the current source by Dommel [26]. This is the origin of the EMTP [9,11]. 

The method presented there can be extended by using the simulation grid itself as an equivalent circuit over which a nodal analysis can be carried out (by using the currents /disk and /ring, as well as the charge transfer and solution resistances as parameters) in order to estimate the electric potential field at each points of the simulation mesh. 

Flow is solved using electrical circuit theory, where airflow is analogous to current flow and flow resistance is caused by fabric permeability and Poiseuille flow resistance through the air gaps between fabric layers. Nodal analysis is used to solve sub-elements of the circuit and identifies each junction and KirchofTs current law is applied to conserve flow at each junction. The model can be modified to represent a complex variation in air gap width and complexities in clothing geometry and structures, such as seams. 

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