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)
Q11. With reference to testing High Voltage equipment:
(a) explain why earthing down is considered essential; (2)
(b) state the operating voltage for an insulation resistance tester (megger) suitable for 6.6 KV equipment; (1)
(c) describe how an insulation resistance test is carried out on High Voltage equipment, making reference to personnel safety; (5)
(d) explain why infra red temperature measurement is used on High Voltage equipment. (2)
Q11. With reference to large electrical transformers on board ships:
(a) state where these transformers may be used; (1)
(b) state a typical efficiency range for a transformer; (1)
(c) state the regulations pertaining to transformers; (3)
(d) state the protective devices that are fitted; (2)
(e) describe the maintenance requirements. (3)
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