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Electrical machines miscellaneous

Electrical Machines

  1. A non-salient pole synchronous generator having synchronous reactance of 0.8 pu is supplying 1 pu power to a unity power factor load at a terminal volt age of 1.1 pu. Neglecting the armature resistance, the angle of the voltage behind the synchronous reactance with respect to the angle of the terminal voltage in degrees is ________.
    1. 33.61°
    2. 13
    3. 31
    4. 41.34
Correct Option: A

Given, P = 1 P.u ;
Vt = 1.1 P.u ;
Xs = 0.8 P.u
Pf = 1

∴ Ia =
P
=
1
= 0.91
V cos φ1.1 × 1

∴ E = √(V cos φ + Ia Ra)² + (V sin φ + Ia Xs
E = √(1.1 × 1 + 0)² + (0 + 0.91 × 0.8)² = 1.314 V
∴ From power equation,
P =
E V
sin δ
Xs

⇒ 1 =
1.314 × 1.1
sin δ
0.8

⇒ δ = 33.61 °



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