1.a) Explain the constructional details of synchronous machine.[7]
b) Where salient pole rotors are preferred. [8]
2.a) What are the advantages and disadvantages of using short – pitched winding and distributed winding in alternator?[7]
b) Derive the expression of coil span factor and distribution factor. [8]
3. With relevant diagrams, explain the effect of load power factor on the armature reaction of alternator. [15]
4. A 3 – phase, star – connected, 1000 KVA, 2000v, 50Hz alternator gave the following open circuit and short – circuit test readings:
Field current : A 10 20 25 30 40 45
O.C voltage : V 800 1500 1760 2000 2350 2600
S.C armature current: A 200 250 300
Armature resistance per phase is 0.2Ω
Draw the characteristics and determine the full load percentage regulation at
a) 0.8 P.F. lead b) 0.8 p.f lag. [15]
5. Draw and explain the phasor diagram of salient pole alternator supplying full load lagging power current. Show the power output per phase[15]
6. Two station generators A and B operate in parallel station capacity of A is 50Mw and that of B is 25 Mw. Full load speed regulation of station A is 3% and full load speed regulation of B is 3.5%. Calculate the load sharing if the connected load is 50MW, No – load frequency is 50Hz. [15]
7. Describe briefly the effect of varying excitation upon armature current and power factor of a synchronous motor when input power to the motor is maintained constant. [15]
8. Explain the principle and constructional features of stepper motor. [15]
b) Where salient pole rotors are preferred. [8]
2.a) What are the advantages and disadvantages of using short – pitched winding and distributed winding in alternator?[7]
b) Derive the expression of coil span factor and distribution factor. [8]
3. With relevant diagrams, explain the effect of load power factor on the armature reaction of alternator. [15]
4. A 3 – phase, star – connected, 1000 KVA, 2000v, 50Hz alternator gave the following open circuit and short – circuit test readings:
Field current : A 10 20 25 30 40 45
O.C voltage : V 800 1500 1760 2000 2350 2600
S.C armature current: A 200 250 300
Armature resistance per phase is 0.2Ω
Draw the characteristics and determine the full load percentage regulation at
a) 0.8 P.F. lead b) 0.8 p.f lag. [15]
5. Draw and explain the phasor diagram of salient pole alternator supplying full load lagging power current. Show the power output per phase[15]
6. Two station generators A and B operate in parallel station capacity of A is 50Mw and that of B is 25 Mw. Full load speed regulation of station A is 3% and full load speed regulation of B is 3.5%. Calculate the load sharing if the connected load is 50MW, No – load frequency is 50Hz. [15]
7. Describe briefly the effect of varying excitation upon armature current and power factor of a synchronous motor when input power to the motor is maintained constant. [15]
8. Explain the principle and constructional features of stepper motor. [15]
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