1. A transformer having 1000 primary turns is connected to a 250 V ac supply. For a secondary voltage of 400 V, the number of secondary turns should be :
2. A 3 phase step down transformer is connected to 6600 V on the primary side. The voltage transformation ratio is (1/12). Find the secondary phase voltage if the transformer is connected in Y-Y.
3. A transformer takes a current of 0.6 A and absorbs 86 W when the primary is connected to its normal supply of 200 V, 50 Hz. The secondary is open circuited. What is the iron loss current component (Iw)?
4. A single phase transformer has 400 primary and 1000 secondary turns. If the primary winding is connected to a 50 Hz supply at 500 V, calculate maximum core flux.
5. The maximum efficiency of a 200 kVA transformer having iron loss of 900 kW and full load Cu loss of 1600 W occurs at _____ kVA.
6. A auto transformer supplies a load of 3 kW at 115 V at a unity power factor. If the applied primary voltage is 230 V, calculate the power transferred to the load (i) inductively and (ii) conductively
7. In a 50 kVA transformer, the iron loss is 500 W and full load Cu loss is 800 W. Determine the total losses at half full load at 0.8 p.f. lagging.
[Hint with simple calculation]