SSE JE Electrical Engineering 29 Oct 2020 Shift 2 Papers

Question : 127 of 200

Marks: +1, -0

A three-phase, six-pole, star-connected alternator has the following specifications:
Flux per pole is 0.1 Wb
54 slots in stator
Double layer winding
Each coil has 8 turns
Coil is chorded by 1 slot.
Find the no-load phase voltage in the alternator running at 1200 rpm. Assume distribution and pitch factors are unity.

1.92 kV
1.82 kV
1.72 kV
2.2 kV

Validate

Solution:

flux (ϕ) = 0.1 Wb
Slots = 54
Turns in each coil = 8
Speed

(\N_\s)

= 1200
Number of poles (P) = 6

\N _{ \s }=1200={120 ×\f }/{6}

⇒ \f = 60 \Hz

Turns per phase

{54}/{3 ×2} ×8=72

\K _{ \c }= \K _{ \d }=1

The no-load phase voltage in the alternator is,
E = 4.44 × 0.1 × 60 × 72 × 1 × 1 = 1.92 kV

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