1. Explain the Kron's primitive machine with its two-pole representation. How is Kron's 'primitive machine equivalent to any rotating electrical machine?

2. What is the physical significance of Park's transformation Deduce Park's transformations relating the 3-phase currents of a machine to its corresponding d-q axes currents.

3. Derive the transfer functions of a separately excited DC generator for no load operation, and on load operation.

4. A separately excited DC generator running at 4500/n rpm has the following parameters:

rf= 80 ohm; Lf=40H; ra=0·1 ohm; La 0·3 mH and
Kg= 120 volts/field amp.

The field is unexcited with open armature. Determine the armature voltage as a function of time, if a constant voltage of 160 V is suddenly impressed across the field terminals.

5. Starting from the impedance matrix of a 3-phase salient pole synchronous machine, derive the phasor voltage equation under balanced steady state operation.

6. Explain the various reactances and time constants from the d-axis equivalent circuit of a 3-phase synchronous machine.

7. A 400 4-pole, 50 Hz, 3-phase squirrel cage induction motor develops full load torque at 1470 rpm and has full load p.f. of 0·85. If the supply voltage reduces to 340 with the load torque remaining constant, calculate the motor speed.

8. Discuss the constructional features and working principle of the following motors:

Single phase series motor

Hysteresis motor

9. Write short notes on any two of the following:

Steady state behaviours of a DC machine

Power angle characteristics of a synchronous machine

Single phase reluctance motor