Electrical Machines
In dc machines, 1. reactance voltage is proportional to armature current 2.reactance voltage is proportional to core length 3.reactance voltage is due to self-flux of the coil undergoing commutation 4. armature-cross flux is neutralized by interpolar flux 5. interpolarmmf is more than armature mmf in the interpolar zone From these, the correct answer is

 1, 2, 5
 1, 3, 5
 2, 3, 4
 1, 2, 3, 4

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Electrical Machines
In a transformer

 OC test is conducted on HV side and SC test is conducted on LV side
 OC test is conducted on LV side and SC test is conducted on HV side
 both Oc and SC tests are conducted on HV side
 both OC and SC tests are conducted on LV side

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Electrical Machines
In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation. Now, if the brushes are given a lead of 90° (electrical), then the MNA will

 shift forward by 90°
 coincide with the GNA
 shift forward by less than 90°
 shift forward by more than 90°

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