1) Describe the two reaction theory applicable to the salient pole synchronous alternators. Describe the slip test for determining the Xd and Xq.
2) find out the synchronous impedance and reactance of an alternator in which the given field current generates an armature current of 200 A on short circuit and a generated E.M.F of 50 V on open circuit. The armature resistance is 0.1 ohm. To what induced voltage must the alternator be excited if it is to deliver a load of 100 A at the PF of 0.8 lagging, with a terminal voltage of 200 V.
3) a) Sketch and describe the V curve and Inverted V curves of a synchronous motor.
b) Describe the working principle of three phase synchronous motor.
4) a) A 500, 1 Phase synchronous motor provides a net output mechanical power of 7.46 KW and operates at the 0.9 pf lagging. Its effective resistance is 0.8 ohm. If the iron and friction losses are 500 W and excitation losses are 800 W, estimate the armature current. Determine the commercial efficiency.
b) A 75 KW,3 phase star connected ,50 Hz ,440v cylindrical rotor synchronous motor operates at rated condition with 0.8 pf leading. The motor efficiency excluding field and stator losses, is 95% and Xs =2.5 ohm. Determine
a) Mechanical power developed
b) Armature current
c) Back E.M.F
d) Power angle
e) Maximum or pull out torque of the motor.
5) Describe the construction, types and the rotating magnetic principle of 3 phase Induction motor.
6) Sketch the circle diagram for the 5.6 KW, 400V, 3 phase, 4 pole, and 50HZ slip ring induction motor from the following data:
Number of load test: 400 V, 6A, cos φ0=0.087.
Short circuit test: 100V, 12A, 720W.
The ratio of primary to secondary terms is 2.62.Stator resistanceper phase is 0.67 OHM and that of the rotor is 0.185 OHM. find out
a) The full load current
b) Full load slip
c) Full load power factor
d) Maximum power and
e)Maximum Torque.
7) Describe with neat sketches the double field revolving theory for single phase induction motor.
8) describe the construction and principle of operation of 1 phase series motor and Universal motor with labelled diagram.
9) Describe the construction and principle of the operation of permanent magnetic synchronous motor.
10) Draw the speed torque characteristics and phasor diagrams of the permanent magnetic synchronous motor and describe.