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. Tank liquid level sensors are an integral part of ships. Describe with the aid of suitable sketches the working principle of:
(a) Capacitive type level sensor (6)
(b) Ultrasonic level sensor (5)
(c) Float (5)

Q3. The direct online start of squirrel cage motor is used for most electrical driven on a.c. powered ships. Describe with sketches as necessary one method of overcoming each of the following problems: (16)

(a) High starting current

(b) Low starting torque

Q4. a) Explain the significance of the root-mean-square value of an alternating current or voltage waveform. Define the form factor of such a waveform. (6)

b) A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000 kW at 0.9 power factor. Find the KVA rating of the other alternator and the power factor. (10)

Q5. A) By means of a schematic circuit diagram illustrate the peak rectifier. If the supply voltage is v(t) = Vm Sinwt, what is the voltage across the load resistor? (6)

b) A battery-charging circuit is shown below in fig. The forward resistance of the diode can be considered negligible and the reverse resistance infinite. The internal resistance of the battery is negligible. Calculate the necessary value of the variable resistance R so that the battery charging current is 1.0 A. (10)

Q6. A) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance. (6)

b) A three-phase induction motor is wound for four poles and is supplied from a 50 HZ system.

Calculate:

(i) The synchronous speed

(ii) The speed of the rotor when the slip is 4 percent

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

Q8. Name various statutory Certificates and Documents to be carried on board Chemical Tankers giving reference to the conventions and justify for their requirement. (16)

Q8. With Reference to the Maritime Labor Convention (MLC) 2006, discuss the requirements for seafarers regarding:

a) Young Seafarers onboard ships (6)

b) Repatriation (5)

c) Seafarers Wages (5)

Q9. With reference to an oil/ water separator:

a) (i) Sketch such a device (4)

(ii) Describe the passage of oil/water mixture from the delivery of pump to the outlets of the separator. (4)

b) State how oil density and temperature affect the case of separation of oil from water. (4)

c) State how the movement of oil on board ship or its discharge and the discharge of oily-bilge or ballast water overboard is recorded. (4)