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when the machine is supplying full load of 20000kVA at zpf, the field current is 42.54
and terminal voltage is 6000V. Determine the field current required when the machine is
supplying full load at 0.8pf lagging. (10)

PART ^
Answer any two questions.

A salient pole alternator has direct and quadrature axis reactances of 80% and 60%
respectively. It is having a resistance of 10%. Determine its regulation if the generator
delivers (i) Full load at rated terminal voltage and 0.8 pf lagging (ii) % th Full load and
0.8pf lagging. (10)
With the help of a phasor diagram explain the parallel operation of alternators under no
load and loaded condition. (10)
Derive the expression for the mechanical power developed in a 3 phase Induction motor
Draw the approximate equivalent circuit also. (10)

PART D
Answer any two questions.

.A2.4 kW, 40017, 50112, 3phase, delta connected slip ring Induction motor has a stator

resiatnce of 0.36Q/phase and a rotor resistance of 0.06Q/phase. Stator to rotor turns ratio
is 2,

No Load test data : 40017, 3.2۸, Cos ‏7ح0‎

Blocked rotor test : 210۷, 16A, Cos ൫,-0.35.

Draw the circle diagram and find line current, pf, efficiency at Full load and

maximum torque. (10)
a) With the help of a neat diagram, explain how an Induction motor can be started using a
star delta starter. (5)

b) Determine approximately the starting torque of an Induction motor in terms of full
load torque when started by means of (i) Star delta starter (ii) Auto transformer with 50%
tapping. Ignore ‏.ىآ‎ The short circuit current of motor at normal voltage is 5 times the full
load current and slip at FLis 5%. (5)
Explain the following starting methods of a single phase Induction motor.

(i) Split phase starting

(ii)Capacitor start- capacitor run starting (10)

اد بد ‎ಸೇರ‏

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