1. Draw a neat sketch of a d.c generator. State the function of each part and explain the principle of operation as a motor and generator? [15]
2. A 4-pole lap-wound dc armature has a bore diameter of 0.7metre. It has 560 conductors and the ratio of pole arc/pole pitch is 0.63. If the armature is running at 600 r.p.m. and the flux density in the air gap is 1.2 wb/m2. Determine the induced emf in the armature if effective length of armature conductor is 20cm. [15]
3. Explain the following
i) period of commutation ii) reactance voltage during commutation
iii) emf commutation iv) resistance commutation. [15]
4.a) What are the different types of d.c generators according to the ways in which fields are excited? Show the connection diagram of each type?
b) Explain the process of building up of voltage in a d.c shunt generators and give conditions to be satisfied for voltage build up? [10+5]
5. A 250V shunt motor runs at 1,000 rpm at no load and takes 8A. The total armature and shunt field resistance are respectively 0.2Ω and 250Ω. Calculate the speed when loaded and taking 50A. Assume the flux to be constant. [15]
6. What are the general methods of speed control of d.c motors and explain them briefly? [15]
7. A 220-V, d.c series motor is running at a speed of 800 r.p.m and draws 100A. Calculate at what speed the motor will run when developing half the rated torque. Total resistance of the armature and field is 0.1Ω. Assume that the magnetic circuit is unsaturated. [15]
8. What are the drawbacks of three-point starter? Describe a four-point starter with a neat
2. A 4-pole lap-wound dc armature has a bore diameter of 0.7metre. It has 560 conductors and the ratio of pole arc/pole pitch is 0.63. If the armature is running at 600 r.p.m. and the flux density in the air gap is 1.2 wb/m2. Determine the induced emf in the armature if effective length of armature conductor is 20cm. [15]
3. Explain the following
i) period of commutation ii) reactance voltage during commutation
iii) emf commutation iv) resistance commutation. [15]
4.a) What are the different types of d.c generators according to the ways in which fields are excited? Show the connection diagram of each type?
b) Explain the process of building up of voltage in a d.c shunt generators and give conditions to be satisfied for voltage build up? [10+5]
5. A 250V shunt motor runs at 1,000 rpm at no load and takes 8A. The total armature and shunt field resistance are respectively 0.2Ω and 250Ω. Calculate the speed when loaded and taking 50A. Assume the flux to be constant. [15]
6. What are the general methods of speed control of d.c motors and explain them briefly? [15]
7. A 220-V, d.c series motor is running at a speed of 800 r.p.m and draws 100A. Calculate at what speed the motor will run when developing half the rated torque. Total resistance of the armature and field is 0.1Ω. Assume that the magnetic circuit is unsaturated. [15]
8. What are the drawbacks of three-point starter? Describe a four-point starter with a neat
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