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Q9. A ship 120 meters long at the waterline has equidistantly spaced half-ordinates commencing from forward as follows 0,3.7,5.9,7.6,7.5,4.6, and 0.1 meters respectively. Find the area of the waterplane using Simpson’s Second rule and the TPC at this draft, Water density is 1.025 t/m3. (16)

Q9. a) Draw a metacentric diagram for a vessel of constant triangle cross-section (6)

b) A block of wood of uniform density has a constant cross-section in the form of a triangle, apex down. The width is 0.5 m and the depth 0.5 m. It floats at a draught of 0.45 m. Calculate the metacentric height (10)

Q7. a) What is the difference between a DC Generator and a DC motor? (6)

b) A 4-pole, 32 conductor, Lap-wound DC shunt generator with terminal voltage of 200 V delivering 12 A to the load has ra = 2 and field circuit resistance of 200 Ω. It is driven at 1000 RPM .

a) Calculate the flux per pole in the machine. (6)

b) If the machine has to be run as a motor with the same terminal voltage and drawing 5 A from mains, maintaining the same magnetic field, find the speed of the machine. (10)

Q9. 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)

Q6. (a) What are the different types of DC motors? (6)

(b) A 10 H.P. 230 V shunt motor takes an armature current of 6A from 230 V mains at no load runs at 1200 r.p.m. The armature resistance is 0.25Ω. Determine speed and electromagnetic torque when the armature takes 36 amps with the same flux. (10)

Q9.a) Explain the principles of A.C. Motors starting and speed control, including the effect on efficiency. (6)

b) A 3-phase induction motor has a 4-pole, Y-connected stator winding. The motor runs on 50-Hz supply with 200V between lines. The motor resistance and standstill reactance per phase are 0.1 Ω and 0.9 Ω respectively. Calculate (a) the total torque at 4% slip (b) the maximum torque (c) the speed at maximum torque if the ratio of the rotor to stator turns is 0.67. Neglect stator impedance. (10)

Q7. (a) Show by means of diagrams how the center of gravity of the liquid in a partly filled tank moves during rolling. (6)

(b) A box barge is 15 m long, 6 m wide and floats in water of 1.016 t/m³ at a draught of 3 m. 150 tonne of cargo is now added. Calculate the load exerted by the water on the sides, ends and bottom. (10)

Q5. a) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance (6)

b) The earth-lamps on a main switchboard comprise two 240V 60W lamps connected in the usual manner. The potential difference at the busbars is 220V. Damage by sea water occurs to a distribution cable so that the insulation resistance to the earth is reduced to 16 ohms and 6 ohms for +ve and -ve cables respectively. Find by calculation:

a) Which of the two lamps burns the brighter; and

b) The additional load on the generators occasioned by the fault. The resistance of the cables and the ship’s structure may be neglected, and that of the lamps taken as constant at the value corresponding to the 60W rating. (10)

Q4. a) What are the characteristics of PN junction diode? Point out its specifications. Also point out the significance of dynamic and static resistances. (6)

b) Draw the circuit of half-wave rectifier and its output waveform. A diode whose internal resistance is 20 Ω is to supply power of 1000 Ω load from 110 V (RMS) source. Calculate

(a) Peak load current

(b) DC load current

(c) AC load current. (10)

Q4. A 4-pole, 500V shunt motor has 720 wave connected conductors on its armature. The full load armature current is 60A, and the flux per pole is 0.3Wb, armature resistance 0.2Ω. Calculate the full load speed of the motor to maintain rated terminal voltage at the full load. (16)

Q6. a) Describe International protection rating and types of insulation. (6)

B. A 72 KVA transformer supplies a heating and lighting load of 12 KW at unity power factor and a motor load of 70 kVA at 0.766 (lagging) power factor: Calculate the minimum rating of the power-factor improvement capacitors which must be connected in the circuit the ensure that the transformer does not become overloaded. (10)

Q9. (a) Describe the effect of running an induction motor on reduced voltage (6)

b) Two 220 V D.C. generators each having linear external characteristics, operated in parallel. One machine has a terminal voltage of 270 V on on-load and 220V at a load current of 35 A, while the other has a voltage of 280 V at no-load and 220 V at 50 A. Calculate the output current of each machine and the bus bar voltage when the total load is 60 A. What is the kW output of each machine under this condition. (10)