Electrical Machines Mock Test 9

1. The stator of a 3-phase, six pole induction motor's stator is connected to 50 Hz supply while its rotor is fed from a 20 Hz supply. The possible speeds at which the machine will run will be?

(i) 1600rpm   (ii) 600rpm (iii) 1400rpm (iv) 400 rpm

2. Considering a transformer at no load is excited at rated voltage. A small recognizable gap is made in the yoke of the limbs. With this altercation, the transformer core flux ___________

3. Consider a 2-winding transformer as below. If the switch is open then the emf induced across the secondary having transformation ratio of 2 is?

4. Which of the following statements are correct for an ideal transformer?

I. Voltages - Direct ratio
II. Current - Inverse ratio
III. Impedance - Direct ratio squared
Iv. Power - Remains same

5. Speed control is possible for _______ and not possible for __________

6. We can employ transformers for a power range of _________

7. The simplex lap winding has the range of winding pitch of _________

8. Which of the following statement is true?

I. Core flux in an ideal transformer remains constant.
II. Core flux is independent of the load current.

9. Consider two transformers X and Y having identical ratings, but have flux densities of 1.5T and 2T respectively. The weight of the transformer B per KVA will be _________

10. Which of the following statements are correct for an ideal transformer?

I. Voltages - inverse ratio
II. Current - direct ratio
III. Impedance - direct ratio squared
Iv. KVA - remains same