Electrical Machines
A 5 KVA transformer has a turns ratio of N1/N2 = 10. The impedance of primary winding is 3+j5 ohms while that of secondary winding is 0.5+j0.8 ohms. The impedance of transformer when referred to primary will be

 3.05+j5.08 ohms
 3.5+j5.8 ohms
 8+j13 ohms
 53+j85 ohms

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Electrical Machines
In a DC shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will

  worsen and terminal voltage will fall
 improve but terminal voltage will fall.
  worsen and terminal voltage will rise.
  improve and terminal voltage will rise .

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Electrical Machines
In the 3-phase induction motor, the resultant flux is of a constant nature and is

 equal to φm, where φm is the maximum flux due to any phase
 1/2 times maximum value of flux due to any phase
 3 times maximum value of flux due to any phase
 3/2 times maximum value of flux due to any phase

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Electrical Machines
Consider the following statements regarding the speed control of dc motors : 1. ward-leonard method is suitable forconstant-torque drives 2. Ward-leonard method is suitable for constant-power drives 3. field-control method facilitates speed control below base speed 4. Armature-resistance control method is more efficient than ward-leanard method 5. Field-control method is suitable for constant-torque drives 6. Armature-resistance control method is suitable for constant-torque drives From these, the correct answer is

 1, 2, 6
 1, 4, 6
 1, 3, 5
 1, 2, 5

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