2.5 Reflection of DC voltage in Transmission lines
59
Figure 2.5-30 Pulse carries on travelling down the line
As the pulse moves down the line current loops are formed which charge capacitors further down
the line and discharge the preceding ones thereby allowing the voltage to travel. This is shown in
Figure 2.5-31.
Figure 2.5-31 Current loops charge capacitors further down the line and discharge preceding ones
As the voltage reaches the end of the line, current I flows through the last inductor but it
cannot flow through the last capacitor since its terminals are shorted. This is shown in Figure 2.5-32
where the end capacitor is greyed out to signify that it cannot be charged.
Figure 2.5-32 Voltage pulse reaches the end of the line
The current however loops around to find some other place to flow! Since capacitors are
symmetrical elements, the penultimate capacitor, which is not charged at this instant in time, is
more than happy to let current flow through from its lower plate and be charged to a voltage equal
to –E/2 (Figure 2.5-34).
E
E/2
I
E/2 E/2
E
E/2
I
E/2 E/2
+
+
E
E/2
I
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