DieselShip's Online Content Library

Q8. A. What are the factors which determine the synchronous speed of a motor?

B. Three conductors fitted side by side in the stator of a salient-pole alternator. Each generates maximum voltage of 200V (sinusoidal). The angle subtended at the centre of the stator between adjacent conductors is 20 electrical degrees. If the three conductors are connected in series, find

(i) the r.m.s. value of the effective voltage and

(ii) the ‘breadth factor’. Using the theory that is the basis of this problem, give one reason why three-phase current has been introduced.

Q6. A. Describe briefly the significance of the factor of sub-division;

B. A box shaped vessel 65m X 12m X 8m has KG 4m and is floating in self water upright on an even keel at 4m draft F and A. Calculate the moments of statically stability at i. 5 degrees and ii. 25 degrees’ heel.

Q1. Describe the relationship between frictional resistance and

(a) Ship’s speed;

(b) the wetted area;

(c) surface roughness;

(d) The length of the vessel.

Q9. A. List the factors that determine the starting torque of the three-phase induction motor. How does this torque generally compare with the value of the rated torque?

B. The low-voltage release of an a.c. motor-starter consists of a solenoid into which an iron plunger is drawn against a spring. The resistance of the solenoid is 35 ohm. When connected to a 220 V, 50 Hz, a.c. supply the current taken is at first 2A, and when the plunger is drawn into the “full-in” position the current falls to 0.7 A. Calculate the inductance of the solenoid for both positions of the plunger, and the maximum value of flux-linkages in weber-turns for the “full-in” position of the plunger.

Q6. A. Describe the normal criteria used for setting thermal protection relays and its advantage compared to magnetic types.

B. The low-voltage release of an a.c. motor-starter consists of a solenoid into which an iron plunger is drawn against a spring. The resistance of the solenoid is 35 ohm. When connected to a 220 V, 50 Hz, a.c. supply the current taken is at first 2A, and when the plunger is drawn into the “full-in” position the current falls to 0.7 A. Calculate the inductance of the solenoid for both positions of the plunger, and the maximum value of flux-linkages in weber-turns for the “full-in” position of the plunger.

Q6. With reference to the circuit breaker for an a.c. generator A. Describe the preventive maintenance carried out on the circuit breaker for an A.C Generator. B. Explain the sequence of events that might occur if the breaker opens on a short circuit and state the check you would require following such event. C. Give a safe procedure to follow should a main circuit breaker fail to open under fault condition.

Q6. With regard to keeping the gas side of boilers in good condition discusses EACH of the following:

A. the mechanism of combustion, stating the factors which are important to good combustion;

B. Oil fuel treatments;

C. Soot removal equipment;

Q4. With reference to preferential tripping in a marine electrical distribution system.

A. With the aid of a sketch, describe a typical arrangement to provide three stages of tripping an instantaneous protection against short circuit.

B. State why this protection is required;

Q1. Describe how each of the following procedure may be accomplished by bridge control equipment for a direct reversing 2 stroke diesel engines - Setting the direction of rotation; Starting; Controlling speed

Q5. Discuss the consequences of failure to maintain correct clearances in the case of main diesel engine crankshaft and bottom end bearings. Sketch a bottom end bearing paying particular attention to the arrangement of ensuring uninterrupted flow of oil to the top end bearing.

Q4. A. Describe with the aid of sketches where necessary a vane type steering gear showing how to weight of the rudder and stock are carried and the arrangement that allow for wear down;

B. State how the vanes described in (A) are secured and the method of sealing the edges;

C. State how, if necessary, the steering gear is locked for rudder maintenance.

Q1. You have been appointed as the Second Engineer of an eight years old vessel, recently purchased by your shipping company. Write a report to the engineering superintendent covering the inspection of main propulsion machinery carried out by you, to ensure its trouble free operation.

Q2. A. Describe the procedure to be adopted for the inspection of a safety valve fitted to an exhaust gas fired auxiliary boiler stating, with reasons, which parts should receive particularly close attention.

B. Describe the procedure for the setting of safety valves of exhaust gas operated auxiliary boilers;

C. Explain the required action a watch-keeping engineer should take after the setting of safety valves as in (B)