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Electrical machines miscellaneous

Electrical Machines

  1. A synchronous generator is connected to an infinite bus with excitation voltage Ef = 1.3 pu. The generator has a synchronous reactance of 1.1 pu and is delivering real power (P) of 0.6 pu to the bus. Assume the infinite bus voltage to be 1.0 pu. Neglect stator resistance. The reactive power (Q) in pu supplied by the generator to the bus under this condition is _________.
    1. 3
    2. 1.12
    3. 3.10
    4. 0.10 to 0.12
Correct Option: D

P =
Ef Vt
sin δ
Xs

⇒ 0.6 =
1.3 × 1
sin δ
1.1

⇒ sin δ = 0.5077
⇒ δ = 30.5°
Reactive power Q (in p.u.) supplied by the generator
=
Ef Vt
cos δ -
Vt2
XsXs

=
1.3 × 1
× 0.8616 -
1
= 0.109 p.u.
1.11.1



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