Electrical Engineering (EE)

A three-phase 220 V supply is applied to a balanced A-connected three phase load. The phase current being Iab =. 10∠-30°A as shown in the given figure, The total power received by the Δ-load is
  • a)
    2250 W
  • b)
    6232 W
  • c)
    5715 W
  • d)
    -2200 W
Correct answer is option 'C'. Can you explain this answer?

AVANEENDRA JODHA answered  •  9 hours ago
Iab = 10∠-30°A
So, 1bc = 10∠-150°A
and Ica = 10∠-270° A
Phase current,
Ia = Iab - I ca = ( 10 ∠- 30° - 10∠-270°) A 
= 10[cos 30° - jsin 30° - cos 270° + jsin 270°]
= 10[0.866- j0 .5 - 0 - j1]
= 8.66-j15 = 17.32 ∠-60° A
∴ Ia = 17.32 ∠-60°A
∴ Total power received
= √3 VLIL cos φL
= 3VPIP cos φph
= 3 x 220 x 10 x cos 30°
= 5715W

Galloping in transmission line conductors arises generally due to
  • a)
    Asymmetrical layers of ice formation
  • b)
    Vortex phenomenon in light winds
  • c)
    Heavy weight of the line conductor configuretions
  • d)
    Adoption of horizontal conductor configuretions
Correct answer is option 'A'. Can you explain this answer?

SHAHIL AGRAWAL answered  •  9 hours ago
Galloping is a low frequency, large amplitude, wind-induced vibration of both single and bundle overhead conductors, with a single or a few loops of standing waves per span. It is caused by moderately strong, steady crosswind acting upon an asymmetrically- iced conductor surface.

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