A three-phase cylindrical rotor synchronous generator has a synchronous reactance Xs and a negligible armature resistance. The magnitude of per phase terminal voltage is VA and the magnitude of per phase induced emf is EA. Considering the following two statements, P and Q, P: For any three-phase balanced leading load connected across the terminals of this synchronous generator, VA is always more than EA Q: For any three-phase balanced lagging load connected across the terminals of this synchronous generator, VA is always less than EA Which of the following options is correct?

P is false and Q is true
P is true and Q is false
P is false and Q is false
P is true and Q is true

LohaHridoy

6 views

2025-01-04 04:42

1 Answers

AhmedNazir

Option 1 : P is false and Q is true

Given that the cylindrical synchronous generator with

Synchronous reactance = X_S and

Armature resistance = R_a = 0

Now, the simplified circuit of the synchronous generator looks like as shown below

[ alt="F1 U.B Madhu 09.05.20 D28" src="//storage.googleapis.com/tb-img/production/20/05/F1_U.B_Madhu_09.05.20_D28.png" style="width: 193px; height: 91px;">

Case 1: The load is lagging in nature.

The corresponding phasor diagram is

[ alt="F1 U.B Madhu 09.05.20 D29" src="//storage.googleapis.com/tb-img/production/20/05/F1_U.B_Madhu_09.05.20_D29.png" style="width: 174px; height: 160px;">

⇒ |V| < |E|

Case 2: The load is leading in nature.

The corresponding phasor diagram is shown below.

[ alt="F1 U.B Madhu 09.05.20 D30" src="//storage.googleapis.com/tb-img/production/20/05/F1_U.B_Madhu_09.05.20_D30.png" style="width: 184px; height: 122px;">

⇒ |V| > |E|

A cylindrical rotor synchronous generator (with R_a = 0) has always positive voltage regulation for lagging p.f. loads i.e. E_A > V_A
Whereas it has positive, zero, and negative regulation for leading loads i.e. all cases E_A > V_A, E_A = V_A, and E_A < V_A are possible.

Therefore, statement P is False, and Q is True.

6 views Answered 2022-09-04 04:29

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