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Q9. (a) Describe, with the aid of a sketch, the constructional details of a squirrel cage rotor as fitted in an induction motor (7)

(b) Explain why some rotors have a double cage. (3)

Q9. Describe the construction and operation of EACH of the following:

(a) Synchronous motor (5)   (b) Induction motor. (5)

Q10. With reference to star delta starters used for three phase induction motors;

(a) explain in detail why this type of starter is employed. (4)

(b) explain, with the aid of a circuit diagram, the sequence of operation of a star delta starter. (6)

Q10. With reference to three-phase induction motor starters:

(a) explain why star-delta starters are employed; (2)

(b) explain what is meant by reduced voltage starting in the context of star-delta starters; (2)

(c) explain, with the aid of a power circuit, the sequence of operation of a start-delta starter. (6)

Q10. Describe how the starting torque of electric induction motors may be improved by using EACH of the following:

(a) wound rotor; (5)            (b) double cage. (5)

Q10. with reference to a.c. induction motors:

(a) state, with reasons, the type of fuses used for protection; (2)

(b) explain the effects of single phasing; (3)

(c) describe how thermistors can be used to protect the motor; (3)

(d) state TWO types of relay that provide electrical overload protection. (2)