Electrical Machines
To have sparkless commutation, the armature reaction effect in a DC machine is neutralized by

 increasing field excitation.
  compensating winding and commutating poles.
 shifting the brush axis from GNA to MNA.
 fixing the brush axis inline with the pole axis.

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Electrical Machines
The result of slip test on a 3-phase, 20 KVA, 400 V, 50 Hz connected salient pole alternator is given below- Phase value: Vmax = 100 V, Vmin = 96 V, Imax = 10 A and I min = 7 A. The direct and quadranature axis reactances are respectively

 8.248 and 9.60 Ω.
 8.248 and 5.54 Ω.
 14.28 and 9.60 Ω.
  14.28 and 5.54 Ω.

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