Super Node: A super node is constituted by two adjacent nodes that have a common voltage
source.
Example: Write the nodal equations by using super node analysis.
Malla Reddy College of Engineering and Technology (MRCET)
Department of EEE ( 2017-18 )
Electrical Circuits EEE Procedure: Step(1): Identify the position of voltage source.Here the voltage source is common to the two
nodes 2 and 3.so, super node is
nothing but the combination of nodes 2 and 3 .
Step (2): Apply KCL to super node and to other nodes.
Applying KCL to this super node (combination of meshes 2 and 3 ), we get
(V2-V1)/R2 + V2/R3 + (V3-Vy)/R4 + V3/R5 = 0...............(1)
Applying KVL to node 1 ,we get
I = V1/R1 + (V1-V2)/R2.................(2)
Step (3): Make the relation between node voltages with voltage source to get third equation.
Third equation is nothing but the relation between VX , V2 and V3 which is
V2 - V3 = Vx..............(3)
Step (4): Solve the above nodal equations to get the node voltages.
Example : Determine the current in the 5 Ω resistor shown in the circuit below
Solution: Applying KCL to node 1:
10 = V1/3 + (V1-V2)/2
V1 [ 1/3 + 1/2 ] - V2 /2 = 10
0.83 V1 - 0.5 V2 = 10.................(1)
Next applying KCL to the super node2&3 :
(V2-V1)/2 + V2/1 + (V3-10)/5 + V3/2 = 0
-V1/2 + V2(1/2 + 1) V3(1/5 + 1/2) = 2
0.5 V1 + 1.5V2 + 0.7 V3 = 2........................(2)
and the third and final equation is:
V2 - V3 = 20.....................(3)
Malla Reddy College of Engineering and Technology (MRCET)
Department of EEE ( 2017-18 )