DieselShip's Online Content Library

Q1. What are semiconductor devices? What are its advantages over thermionic devices? With respect to semiconductor devices describe working principle and application of the following: (16)

(a) Zener Diode

(b) Transistor

(c) Photocell

(d) Thyristor

Q2. Diesel electric propulsion is now being chosen as the power plant for an increasingly wide variety of vessels. (16)
a) Sketch a simple layout of such an installation.
b) Explain the advantages of selecting such a plant.

Q3. With reference to an emergency source of electrical power in cargo ships: -
a) Describe a typical power source. (8)
b) Give a typical list of essential services, which must be supplied simultaneously. Explain how the emergency installation can be periodically tested. (8)

Q4. With respect to circuit breakers:

a) Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse. (6)

b) A coil having a resistance of 10 ohm and an inductance of 0.15 H is connected in series with a capacitor across a 100 V, 50 Hz supply. If the current and the voltage are in phase what will be the value of the current in the circuit and the voltage drop across the coil? (10)

Q5. With reference to three phase induction motors:

a) Explain the phenomenon of crawling and cogging in these motors (6)

b) A three-phase induction motor is wound for four poles and is supplied from a 50 Hz System calculate:

a) The synchronous speed

b) The speed of rotor when the slip is 4 per cent.

c) The rotor frequency when the speed of the rotor is 600 r/min. (10)

Q6. a) Describe the working of a single-phase full wave rectifier with a resistive load. Draw the load voltage and current waveforms. (8)

b) Diode half wave rectifier supply a resistive load of 100Ω from a 100 V ac r.m.s voltage source. The diode is a resistance of 5Ω during conduction state. Calculate

i) The DC output voltage

ii) DC average load current (8)

Q7. What statutory certificates need to be carried by an Indian flagged general cargo vessel? Name the certificates and state the validity of each of the certificates. (16)

Q8. For an ISM certification, explain the key clauses, which are required to be complied with obtaining Interim DOC, State the responsibility of a ETO with respect to satisfactory implementation of SMS on board ship. (16)

Q9. a) Sketch a line diagram of a mechanical low expansion foam fixed firefighting system suitable for machinery spaces. (6)
b) Describe the operation of the system sketched. (6)
c) Explain how a mixture of foam making compound and sea water are converted into foam. (4)