DieselShip's Online Content Library

Q6. A) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance. (6)

b) A three-phase induction motor is wound for four poles and is supplied from a 50 HZ system.

Calculate:

(i) The synchronous speed

(ii) The speed of the rotor when the slip is 4 percent

(iii) The rotor frequency when the speed of the rotor is 600 r/min. (10)

Q5. A 400V, 4-pole, 50 Hz, 3-phase, 10 hp, star connected induction motor has a no load slip of 1% and full load slip of 4%, find the following:

(i) Syn speed

(ii) No -load speed

(iii) Full load speed

(iv) Frequency of rotor current at full load

(v) Full – load torque (16)

Q6. a) Describe the working of a single-phase full wave rectifier with a resistive load. Draw the load voltage and current waveforms. (8)

b) Diode half wave rectifier supply a resistive load of 100Ω from a 100 V ac r.m.s voltage source. The diode is a resistance of 5Ω during conduction state. Calculate

i) The DC output voltage

ii) DC average load current (8)

Q8. A. What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance.

B. A three- phase induction motor is wound for four poles and is supplied from a 50 Hz system. Calculate.

i. The synchronous speed; (4)

ii. The speed of the rotor when the slip is 4 per cent; (3)

iii. The rotor frequency when the speed of the rotor is 600 r/min. (2)

Q9. A. Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests?

B. A 25 kVa signal phase transformer 2200:200V has a primary and secondary resistance of 1Ω and 0.01 Ω respectively. Find the equivalent secondary resistance and full load efficiency at 0.8pf lagging, if the iron losses of the transformer are 80% of the full load copper losses.

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.

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.

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.

Q8. A box shaped vessel is 80 m long, 12 m wide and floats at a draught of 4m.

A full width midships compartment 15 m long is bilged and this results in the draught increasing to 4.5 m. Calculate EACH of the following,

(a) The permeability of the compartment;

(b) The change in metacentric height due to bilging.

Q4. A ship of displacement 11000 tonne has a length 120 m, breadth 16 m, and even keel draught of 5.5 m in sea water of density 1025 kg/m3. The area of the waterplane is 1440 m2 and the second moment of area of the waterplane about a transverse axis through midships is 1.2 × 106 m4 with the LCF at midships. The ship has a full depth empty rectangular compartment of length 12 m and breadth 10 m.  The center of the compartment is on the centerline of the ship 40 m forward of midships.

Calculate the end draughts after the compartment is bilged.