ECE 524: Session 6; Page 1/2
Transients in Power Systems Spring 2018
Energy Dissipated in Resistor: RC Network
100ohm
I IS
VC1 VC2
U
U(0)
U(0)
2507.17uF
+
+
1253.58uF
Initial energy in circuit
C1 VC1 ( 0) C2 VC2 ( 0)
1 2 1 2
E ( 0) =
2 2
Final energy in the circuit
VC1 ( ∞) = VC2 ( ∞)
C1 C2 VC1 ( ∞)
1 2
E ( ∞) =
2
Energy is conserved:
E ( 0) = E ( ∞) Ediss
Rewriting
Ediss = E ( 0) E ( ∞)
1 2 1 2
Ediss = C1 VC1 ( 0) C2 VC2 ( 0) C1 C2 VC1 ( ∞)
2 1
( 1)
2 2 2
ECE 524: Session 6; Page 2/2
Transients in Power Systems Spring 2018
Now try to simplify the expression.
Recall that charge is also conserved:
q ( 0) = q ( ∞)
C1 VC1 ( 0) C2 VC2 ( 0) = C1 C2 VC1 ( ∞)
VC1 ( ∞) =
C1 VC1 (0) C2 VC2 (0)
C1 C2
Substitute into equation (1)
C1 VC1 ( 0) C2 VC2 ( 0)
2
2 1
Ediss = C1 VC1 ( 0) C2 VC2 ( 0) C1 C2
1 2 1
2 2 2 C1 C2
1 C1 C2 C1 VC1 ( 0) C2 VC2 ( 0) C1 VC1 ( 0) C2 VC2 ( 0)
2 2 2
Ediss =
2 C1 C2 C1 C2
1 C1 VC1 ( 0) C1 C2 VC1 ( 0) C1 C2 VC2 ( 0) C2 VC2 ( 0) C1 VC1 ( 0) 2 C1 C2 VC1 ( 0) VC2 ( 0) C2 VC2 ( 0)
2 2 2 2 2 2 2 2 2 2
Ediss =
2 C1 C2 C1 C2
Ediss =
1 C1 C2
2 2
1 C1 C2
VC1 ( 0) 2 VC1 ( 0) VC2 ( 0) VC2 ( 0) =
2 C1 C2
VC1 ( 0) VC2 ( 0)
2 C1 C2
2