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Electrical Machines 2010 Question Paper For CBSE Class XII Exams

1. Draw a neat circuit diagram of a compound motor and give its applications. Explain how a compound motor combines the advantages of both shunt and series type of d.c motors. (4+2+4 Marks)

OR

Explain why a starter is required for starting a d.c shunt motor. Draw the connection diagram of a starter in conjunction with a d.c. shunt motor complete with protective devices. Write the function of protective devices.

2. (a) What is a diode? What are its applications in half wave and full wave rectifiers? Explain with diagrams. (1+2+2 Marks)

(b) What is transistor? What is its use in a voltage stabilizer? (3 Marks)

3. (a) Explain the difference between ordinary transformer and auto transformer. (4 Marks)

(b) A 55kva, 11000 V/220 V, 50 Hz single-phase transformer has 50 turns on the Secondary side. Determine (2+2+2 Marks)

(i) Number of turns on primary side
(ii) Value of primary and secondary current at full load
(iii) Transformation ratio

4. (a) Describe the construction and principle of operation of a 1 - phase capacitor run Induction motor with neat sketches.(6 Marks)

(b) What are various faults which are likely to occur in a 1- phase Induction? Motor? Write their remedies.(6 Marks)