DieselShip's Online Content Library

Q5. With Reference to different types of transformers used onboard.

a) Discuss the basic principle of operation of a transformer (5)

b) Enumerate the different types of transformers used onboard also state their functions for which they are used. (5)

c) A 440/110 V single phase transformer supplies a load of 5kW at 0.8 power factor load. Calculate the primary and secondary currents. (Ignoring transformer power losses)? (6)

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)

Q2. With Respect to Insulated and Earthed Neutral Systems used on board:

a) Discuss the Advantages and Disadvantages of both Insulated and Earthed Systems used on board. (8)

b) Discuss the consequences of earth fault in an earthed distribution system. (4)

c) What would be the Ohmic value of the NER to limit the earth fault to the full load rating of a 2 MW, 0.8 pf, 3.3KV, 3Phase A.C. generator? (4)

Q4.a) Explain the construction and principle of operation of permanent magnet moving coil instrument. (8)

b) A permanent magnet moving coil instrument has a coil of dimension 15 mm × 12mm. The flux density in the air gap is 1.8 × 10-3 wb/m2 and the spring constant is 0.4 × 10-6 Nm / rad. Determine the number of turns required to produce an angular deflection of 900 when a current of 5 mA is flowing through the coil. (8)

Q5. Explain with the help of a neat diagram the operation of a brushless alternator. What would likely happen if one of the rotating Diode fails and becomes: (16)

a) An open circuit?

b) A short circuit?

Q5. a) Which has the greater equivalent resistance; two equal capacitors in series or in parallel? Explain with reasons? (6)

b) A circuit has a resistance of 3Ω inductance of 0.01H. The voltage across its end is 60V and the frequency is 50Hz. Calculate

a) the impedance

b) the power factor

c) the power absorbed. (10)

Q1. With respect to generators and main circuit breakers and their protection devices:

a) What are safeties incorporated in Air circuit breaker (ACB) of ship’s generator and prime mover? (10)

b) Write Short Note on Negative phase Sequence Relay. (6)

Q7. With reference to entry into enclosed spaces onboard:
a) Define “Enclosed space” and give example of enclosed spaces onboard (6)
b) Describe the checks done for testing the atmosphere inside such enclosed spaces. (5)

c) Explain safety precautions taken prior to entry into enclosed spaces onboard vessel. (5)

Q7. With Reference to Electrical Safety onboard a vessel:

a) Write Short note on “Electric Shock” (6)

b) Enumerate the relation between Shock Current Levels, the Applied Voltage and the Body resistance. (5)

c) How do you treat a person who has suffered an electric shock onboard from a AC supply? (5)