Electrical Machines Mock Test 10

1. Which of the above are correct for an auto transformer when compared to the identical rating two winding transformer?

I. KVA rating : 1/(1-k)
II. Losses : (1-k)
III. Impedance drop = 1/(1-k)

2. From the above graph of the core losses per cycle is, the eddy losses per phase for a transformer at a operating frequency of 40 Hz is?

3. In a transformer ______ decreases with increase of the leakage flux.

4. Two single phase transformers A and B are operating in parallel having different impedance and identical x/r ratio. Impedance of A is Za and impedance of B is Zb, both sharing a load of Sl. Then the load shared by transformer A is?

5. A 200/400 V single phase transformer has leakage impedance z= r+jx. Then we can expect magnitude of load pf of ____ at zero voltage regulation.

6. Transients currents are maximum in the transformer when it is switched on with secondary ______ and when input voltage wave is passing through ________

7. From the above graph of the core losses per cycle is, the hysteresis losses per phase for a transformer at a operating frequency of 40 Hz is?

8. While conducting open circuit test and short circuit test on a transformer, status of low-voltage and high-voltage windings will be such that in ____________

9. The voltage regulation of a transformer at full-load 0.8 p.f lagging is 2%. Its voltage regulation at full load 0.8 p.f leading _____________

10. If para magnetic core is used in the place of the ferromagnetic core of the transformer, then magnetostriction will ___________