Q9. With reference to voltage variation profiles caused by load changes imposed on alternating current generators when starting large motors online:
(a) sketch a voltage dip, showing an acceptable recovery time; (2)
(b) state FOUR salient factors that cause the variation in part (a); (4)
(c) outline FOUR salient factors that assist recovery from the deviation shown in part (a). (4)
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)
Q11. With reference to the protection of electrical power circuits:
(a) explain discrimination, describing how it is achieved. (5)
(b) state, with reasons, the type of fuses used for protection; (3)
(c) explain preferential tripping. (2)
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