1. The magnitude of terminal voltage decreases, and the field current does not change.
  2. The magnitude of terminal voltage increases, and the field current does not change.
  3. The magnitude of terminal voltage increases, and the field current increases.
  4. The magnitude of terminal voltage does not change and the field current decreases.
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1 Answers

Option 1 : The magnitude of terminal voltage decreases, and the field current does not change.

A long transmission line under no-load conditions behaves as the capacitive load. The effect of armature current is purely magnetization. When the alternator is disconnected, there is no magnetizing effect. So the terminal voltage decreases with the same field current.

Explanation:

When the generator is connected to an open-circuit transmission line, the line draws a charging current, therefore Vt > Eg.

[ alt="F1 Jaiprakash Madhuri 02.02.2022 D1" src="//storage.googleapis.com/tb-img/production/22/02/F1_Jaiprakash_Madhuri_02.02.2022_D1.png" style=" width: 173px; height: 123px;">

But, when the generator is disconnected from the line, no charging current is delivered by the generator, i.e.,

Ic = 0 ⇒ Vt = Eg.

So, the terminal voltage decreases.

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