DieselShip's Online Content Library

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)

Q7. A. By means of a schematic circuit diagram illustrate the peak rectifier. If the supply voltage is v(t) = Vmsinwt, 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)

Q10. With reference to 3-phase transformers;

(a) Discuss the essential and desire conditions to be fulfil for operating two three-phase transformers in parallel.

(b) What are the advantages of transformer bank of three 1-phase transformers over a unit three phase transformer of the same kVA rating?

(c) In a 25 kW, 3300/233V, 1- phase transformer the iron and full load copper losses are 350 watts and 400 watts respectively. Calculate the efficiency  at half load, 0.8 p.f.

Q1. Two Diesel Generators running in parallel with D/G # 1 having 2000 KW capacity having 3 % speed droop setting and D/G # 2 having 2000 KW capacity with 4% speed droop settings. The frequency for Diesel Generator on no load has been set at 62 Hz.

A) Calculate the load on each Diesel Generator KW if total ship load is 1000 KW. B) Justify the load difference shared by both Diesel Generator.

Q8. A. What is slip? What are the factors on which the torque or an induction motor depends? B. A 220-V, 3-  4-pole, 50Hz, Y-connected induction motor is rated 3.73 KW The equivalent circuit parameters are: R1=0.45 , X1=0.8 , R2=0.4 , B0=1/30ohm. The stator core loss is 50W and rotational loss is 150W. For a slip of 0.04, find (i) input current (ii) p.f. (iii) air-gap power (iv) mechanical power (v) electro-magnetic torque (vi) output power and (vii) efficiency?

Q10. Evaluate for a frequency of 15 kHz, the amplification and the phase difference between input and output signals of a voltage amplifier using a triode having an amplification factor of 48 and a mutual conductance of 1.2 m A/V with an anode-load resistant of 160 k . The output p.d. is fed by a coupling capacitor of negligible reactance to a subsequent circuit of resistance 480 k and the total shunt capacitance is 90µ F.

Q6. A. Describe how the force on the ship’s bottom and the GM vary when grounding takes place. (6)

B. A ship of 8,000 tonnes displacement takes the ground on a sand bank on a falling tide at an even keel draft of 5.2 metres. KG 4.0 metres. The predicted depth of water over the sand bank at the following low water is 3.2 metres. Calculate the GM at this time assuming that the KM will then be 5.0 metres and that mean TPC is 15 tonne. (10)

Q10.  The breadth of the upper edge of a deep tank bulkhead is 12 metres. The vertical heights of the bulkhead at equidistant intervals across it are 0, 3, 5, 6, 5, 3 and 0 metres respectively. Find the depth of the centre of pressure below the waterline when the tank is filled to a head of 2 metres above the top of the tank. (16)

Q10. A. Explain the effects on stability when a tank is partially filled with liquid.

B. A ship of 11200 tonne displacement has a double bottom tank containing oil. Whose centre of gravity is 16.5m forward and 6.6m below the centre of gravity of the ship? When the oil is used the ship’s centre of gravity moves 380mm calculate - (i) The mass of oil used; (ii) The angle which the centre of gravity moves relative to the horizontal.

Q7. The values of effective power (naked hull) given in Table Q5 refer to a ship which is to have a service speed of 17.75 knots.

The following data also apply:
appendage allowance = 8%
weather allowance = 15%
quasi propulsive coefficient = 0.7
transmission losses = 3%
engine mechanical efficiency = 85%
ratio of service indicated power to installed machinery indicated power = 0.9

A. Determine the indicated power of the engine to be installed.

B. Determine the speed obtained if all the available power of the engine is used in EACH of the following:
(i) when the ship is running on acceptance trial in calm conditions;
(ii) when operating under actual service conditions.