1. Describe with neat sketch, the constructional details of salient pole alternators.
[15]
2. A 3-phase, 8-pole, 750 rpm star – connected alternator has 72 slots on the armature. Each slot has 12 conductors and winding is short chorded by 2 slots. Find the induced emf between lines, given the flux per pole is 0.06 wb. [15]
3. What is armature reaction? Explain the effect of armature reaction on the terminal voltage of an alternator at
i) Unity power factor load
ii) Zero loading P.F load
iii) Zero lagging P-F load and draw the corresponding phasor diagrams. [15]
4. A straight – line law connects terminal voltage and load of a 3-phase star – connected alternator delivering current at 0.8 P.f lagging. At no load, the terminal voltage is 3500V and at full load of 2280kw, it is 3300v. Calculate the terminal voltage when delivering current to a 3-phase, star- connected load having a resistance of 8Ω and a reactance of 6Ω per phase. Assume constant speed and field excitation. [15]
5. A synchronous generator operates on constant - voltage constant frequency bus bars. Explain the effect of variation of a) excitation b) steam supply on power output ,power factor, armature current and load angle of the machine. [15]
6. Explain the effect of varying excitation on armature current and power factor in a synchronous motor. Draw V – curves and state their significance. [15]
7. A 3000V, 3-phase synchronous motor running at 1500 y.p.m has its excitation kept constant corresponding to no – load terminal voltage of 3000V. Determine the power input, power factor and torque developed for an armature current of 250A if the synchronous reactance is 5Ω per phase and armature resistance is neglected.
[15]
8. Discuss the principle of operation of single phase capacitor start and capacitor run motors. [15]
[15]
2. A 3-phase, 8-pole, 750 rpm star – connected alternator has 72 slots on the armature. Each slot has 12 conductors and winding is short chorded by 2 slots. Find the induced emf between lines, given the flux per pole is 0.06 wb. [15]
3. What is armature reaction? Explain the effect of armature reaction on the terminal voltage of an alternator at
i) Unity power factor load
ii) Zero loading P.F load
iii) Zero lagging P-F load and draw the corresponding phasor diagrams. [15]
4. A straight – line law connects terminal voltage and load of a 3-phase star – connected alternator delivering current at 0.8 P.f lagging. At no load, the terminal voltage is 3500V and at full load of 2280kw, it is 3300v. Calculate the terminal voltage when delivering current to a 3-phase, star- connected load having a resistance of 8Ω and a reactance of 6Ω per phase. Assume constant speed and field excitation. [15]
5. A synchronous generator operates on constant - voltage constant frequency bus bars. Explain the effect of variation of a) excitation b) steam supply on power output ,power factor, armature current and load angle of the machine. [15]
6. Explain the effect of varying excitation on armature current and power factor in a synchronous motor. Draw V – curves and state their significance. [15]
7. A 3000V, 3-phase synchronous motor running at 1500 y.p.m has its excitation kept constant corresponding to no – load terminal voltage of 3000V. Determine the power input, power factor and torque developed for an armature current of 250A if the synchronous reactance is 5Ω per phase and armature resistance is neglected.
[15]
8. Discuss the principle of operation of single phase capacitor start and capacitor run motors. [15]
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