Electrical Machines
A compound dc generator is delivering full load current at a terminal voltage of 230 V. Its series-field winding gets short circuited. If its terminal voltage 1. becomes more than 230 V, it is overcompounded generator 2. becomes more than 230 V, it is differentially compounded generator 3. becomes less than 230 V, it is overcompounded generator 4. becomes less than 230 V, it is differentially compounded generator 5. becomes less than 230 V, it is level compounded generator From these, the correct answer is

 1, 4
 2,3
 2, 3, 5
 1, 4, 5

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

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Electrical Machines
What is/are the necessary conditions for voltage build up in self excited generator?

 Field winding resistance should be less than critical resistance.
 Poles should contain residual flux.
All of these
 Field winding should be properly connected to armature winding.

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Electrical Machines
Which of the following statements is/are correct statements?

 EMF per turn in HV winding is more than EMF per turn in LV winding
 EMF per turn in HV winding is less than EMF per turn in LV winding
 EMF per turn in both the windings are equal
All of these

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