Electrical Machines
Which of the following is/are the advantages of carbon brush over the copper brush?

 They are not hard as copper brush
 In case of any sparking they will be less damaged than copper brushes
 They are self lubricating in nature
All of these

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

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Electrical Machines
In synchronous generator, inverted V curve is drawn between

 field current on X-axis and armature current on Y-axis
 field current on X-axis and power factor on Y-axis
 field current on Y-axis and armature current on X-axis
 field current on Y-axis and power factor on X-axis

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