DieselShip's Online Content Library

Q1. With reference to the protection of electric motors explain EACH of the following:

(a) Fuse back up protection (6)

(b) How a motor fitted with fuse back up protection may exceed its rated temperature without being tripped by the primary protection (6)

(c) The value of current rating at which the over current relay should be set (4)

Q7. a) State the conditions, which must be satisfied before an A.C generator can be paralleled with live bus-bars. (4)

b) Sketch a lamp-bright configuration for synchronizing lamps. (8)

c) State the advantages and disadvantages of the lamps-bright system over lamps-darks system. (4)

Q3. (a) Sketch, the circuit diagram of an instrument used for measuring electrical insulation resistance. (8)

(b) Describe the circuit diagram sketched in (a), explaining how it operates when measuring electrical insulation resistance. (8)

Q1. a) Explain the working principle of an alkaline battery. (8)

b) Compare the alkaline battery with Lead-Acid battery. (8)

Q4. a) What is the purpose of AVR in an alternator? (6)

b) With the aid of a simple circuit diagram explain the basic working of a brushless alternator. (10)

Q7. In the following circuit, E1 = 13 V, E2 = 19.5 V, R1 = 5 W, R2 = 7 W, R3 = 9 W. Find the current flowing through each resistor. (16)

Q7. A 24V emergency battery is to be charged from the 110V ship's mains when the e.m.f. per cell has fallen to a minimum value of 1.8V. The battery consists of 12 cells in series, has a capacity of 100 Ahr at a 10 hr rate and the internal resistance is 0.03Ω/cell. If charging continues until the voltage per cell rises to 2.2V, find the value of the variable resistor needed to control the charging. The charging current can be assumed to be equal to the maximum allowable discharge current (16)

Q9. A wooden ring having a mean diameter of 200 mm and a cross-sectional area of 400 mm2 is wound uniformly with a coil of 300 turns. If the current passed through the coil is 5 A calculate the value of flux produced in the coil. (16)

Q6. A coil of resistance 10 ohm and inductance 0.1H is connected in series with a capacitor of capacitance 150pF, across a 200 V, 50 Hz supply.

Calculate:

a) the inductive reactance. (3)

b) the capacitive reactance. (3)

c) the circuit impedance. (2)

d) the circuit current. (2)

e) the circuit power factor. (2)

f) the voltage drop across the coil. (2)

g) the voltage drop across the capacitor. (2)