Q1. What is Zener diode and how does it regulate the voltage? What happens to the series current, load current and Zener current when the d.c input voltage of a Zener regulator increases? Draw a neat diagram of Zener regulator and explain. (16)
Q2. a) Explain why it is necessary to have reverse power protection for alternators intended for operation. (6)
b) (i) Sketch a reverse power trip. (5)
(ii) Briefly explain the principle on which the operation of this power trip is based and how tripping is activated. (5)
Q3. a) Write a short note on the principle of operation of induction motors (8)
b) What is slip for an induction motor? (4)
c) If a 4-pole motor is supplied at 60Hz and runs with a slip of 5%. What is the actual rotor speed? (4)
Q3. With Respect to PLC’s used onboard ships:
a) Draw and explain the block diagram of a PLC. (8)
b) Name the onboard ship equipment where PLC’s are used. (4)
c) What are the advantages of PLC controllers over other type of controllers? (4)
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