Electrical Machines Practice Test 10

1. A 2000/1000/500 three winding transformer is to be used as auto transformer with supply of 3000 V. Two loads of 1050 kVA at 3500V and other one at 180 kVA at 1000V. The total kVA supplied will be?

2. There is a 10 KVA, 2000/200 V, single phase transformer operating at 50 Hz. Maximum flux linkages in secondary will be?

3. When a transformer winding suffers a short circuit, then inter turns of the same winding experience ______ forces.

4. A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:

HV : r = 2.4  ‎Ω, X = 6 ‎Ω, Primary
LV: r = 0.03  ‎Ω, X = 0.07 ‎Ω, Secondary

The secondary reactance referred to primary is?

5. Identify the phasor diagram for the zero voltage regulation from the below diagrams.

6. In a transformer, we place the tapping windings at the middle because __________

7. Which if the conditions is must be fulfilled for satisfactory parallel operation of transformers?

8. Which of the following is a shortcoming for using parallel connected transformers?

I. Reliable loading
II. Increased capacity of power system
III. Reducing the capacity of substation
 

9. 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?

10. The efficiency of a 20 KVA, 2000/200 V, single phase transformer at unity pf is 98%. The given total losses at full load is 200 W. The pu resistance is?