Electrical Machines
The results of a slip test for determining direct axis (Xd) and quadrature axis (Xq) reactances of a star connected salient pole alternator are given below Phase values: Vmax = 108 V ; Vmin = 96 V Imax = 12 A ; Imin = 10 A Hence the two reactances will be

 Xd = 10.8Ω and Xq = 8Ω
 Xd = 9Ω and Xq = 9.6Ω
 Xd = 8Ω and Xq = 10.8Ω
 Xd = 9.6Ω and Xq = 9Ω

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Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

 1 and 3
 1, 2, and 3
 1, 2 and 4
 2, 3 and 4

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