Nodal analysis

The node voltage analysis performed by PSpice is for DC node voltages only. This analysis solves for the DC voltage at each node of the circuit. If any AC or transient sources are present in the circuit, those sources are set to zero. Only sources with an attribute of the form DC=l/ff/i/ff are used in the analysis. If you wish to find AC node voltages, you will need to run the AC Sweep described in Part 5. The node voltage analysis assumes that all capacitors are open circuits and that all inductors are short circuits. 

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The H AZOP leader selects an appropriate aspect of the plant s process systems (a process node) and associated systems that affect the selected process variable for the selected mode of plant operation. The selection may be made fiom the plant system classification, or it may be from the nodal analysis of the process. 

We will perform the nodal analysis on the circuit wired in Part 1 and shown on page 36. The circuit is repeated... 

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 DC Nodal Analysis finds the DC voltage at every node in the circuit. The voltages are relative to ground. 

The IPROBE and VIEWPOINT parts can be used to view the results of the Nodal Analysis on the schematic. 

The DC Sweep can be used to find DC voltages and currents for multiple values of DC sources. It can answer the following question in one simulation What is the voltage at node 1 for VI = 10 VDC, VI = 11 VDC, and VI = 12 VDC This question could be answered using the DC Nodal Analysis if the DC Nodal Analysis were run three times. 

In nodal analysis, the voltages between adjacent nodes of the network are chosen as the unknowns. This can commonly be achieved by selecting a reference node from the graph of the network. Equations are then formed if KCL is employed. By equating the sum of the currents flowing through admittances associated with one node to the sum of the currents flowing out of the current sources associated with the same node, a set of equations can be established with the form of [F][V] = [/] ... 

N. Zhou, J.V. Clark, K. S.J. Pister, Nodal analysis for MEMS design using SUGAR version 0.5, Proc. Int. Conf. Modeling and Simulation of Microsystems, Semiconductors, Sensors and Actuators, MSM98, Computational Publications, Cambridge MA, USA, April 1998, 308-313. 

Some What-lf questions that can be used for a nodal analysis are listed below. 

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]. 

In the EMTP, the nodal analysis method is adopted to calculate voltages and currents in a circuit. Figure 1.68 shows an example. By applying Kirchhoff s current law to nodes 1-3 in the circuit ... 

It is clear from Equation 1.265 that once the node conductance matrix is composed, the solution of the voltages is obtained by taking the inverse of the matrix, as the current vector (J) is known. In the nodal analysis method, the composition of the nodal conductance is rather straightforward, as is well known in circuit theory. In general, nodal analysis gives a complex admittance matrix because of jcoL and jcoC. 

Figure 8. Illustration of the results that nodal analysis on a given simulation grid can yield. The potential values (positive at the disk and negative at the ring) are different throughout the simulation mesh the 7i -drop affecting the 2 working electrodes thus depends on the position of the Luggin capillary.

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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