DieselShip's Online Content Library

Q1. With reference to the provision of a shore electrical supply to a ship:

A. Sketch an arrangement for taking A.C. shore supply and checks to be carried out prior taking shore connection?

B. Describe the method of safely connecting the arrangement sketched in (A) to the shore Supply?

Q2. What is soft starting of an Induction motor? Describe with a circuit using thyristors used for soft starting. Discuss its advantages and dis-advantages.

Q4. A. Describe with the aid of a simple sketch the arrangement of the three-phase winding of an alternator showing the neutral point.

B. Explain why for most ships the neutral point is insulated.

C. Explain why in some installation the neutral point is earthed?

Q4. Differentiate with the aid of simple sketches between two of the following types of electronic circuits.

A. Rectifier circuit (6)

B. Amplifier circuit (5)

C. Oscillator circuit (5)

Q5. With reference to Marine Electrical Circuits:

A. Explain three methods of overcurrent protection for electrical circuit.

B. Explain with aid of diagram, the meaning of the term inverse current time characteristic.

Q6. A. Explain distribution factor and pitch factor for alternator windings.

B. A 3phase, 4pole 24 slot alternator has its armature coils short pitched by one slot. Find the distribution factor and pitch factor.

Q7. A. Describe how protection against short circuit is provided in a 3 phase induction motor circuit.

B. Explain how rotating magnetic field is produced in three phase winding with three phase supply. A 4-pole, 3-phase induction motor operates from a supply whose frequency is 50 Hz. Calculate

(i) Speed at which the magnetic field of the stator is rotating,

(ii) speed of the rotor when the slip is 0.04,

(iii) the frequency of the rotor current when the slip is 0.03.

Q8. A. Explain the significance of the root mean square value of an alternating current or voltage wave form; Define the form factor of such a wave form.

B. Two 10 MVA 3 phase Alternator operate in parallel to supply at 0.8 power factor with lagging load of 15 MVA. If the output of one Alternator is 8 MVA at 0.9 lagging.

1. Calculate the output of second Alternator.

2. Calculate the value of Power factor of second Alternator.

Q9. A. Briefly describe the maintenance routines carried out for emergency batteries onboard.

B. A power of 36 W is to be dissipated in a register connected across the terminals of a battery, having emf of 20V and an internal resistance of 1Ω. Find (i) What value of resistance will satisfy this condition. (ii) The terminal voltage of the battery for each of the resistances and (iii) The total power expenditure in each case.

Q8. A. Sketch an arrangement showing the principal of proportional plus integral (P+I) control loop.

B. Compare the series and parallel resonance circuits. Find the frequency at which the following circuit resonates.