1. Draw the equivalent circuit of a single phase transformer and show how the constants of primary and secondary windings may be combined to give a simplified equivalent circuit with the values of constants given in terms of the secondary winding.

Explain the construction and working principle of an auto-transformer.

Explain the parallel operation of a single-phase transformer.

3. Describe the heat-run test of a single phase transformer, with the circuit diagram. What are the limitations of the test?

Derive the e.m.f. equation of a d.c. generator.

The induced e.m.f. in a d.c. machine when running at 500 r.p.m. is 180 V. Calculate the induced e.m.f. while the machine is running at 600 r.p.m. by assuming flux to be constant.

What is the function of armature winding? Explain different types of winding in d.c. machines.

Explain the armature reaction in a d.c. machines.

Draw and explain the torque -current characteristics of shunt, series and compound motors.

Draw the connection diagram of two shunt generators connected in parallel and discuss their load sharing.

7. Write technical notes on any two of the following:

Commutation of d.c. machines

Open-delta connection of three phase transformer

Testing of three phase transformer