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Maritime Forum

Topics in Category: Marine electrotechnology

emo
Views: 95
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:48 by anandgardener
With reference to the cylinder lubrication of a large slow speed engine: A. explain, with the aid of a sketch, the operation of a cylinder lubricator, indicating how quantity adjustments may be conducted; B. state the advantages and disadvantages of the relative vertical positions of cylinder...
emo
Views: 83
Replies: 0
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Topic started 18 Jan 2012 17:47 by anandgardener
With reference to bottom end bolts for medium speed four stroke engines: A. explain why bottom end bolts may ultimately fail under normal operating conditions; B. identify the features incorporated into bolt design to inhibit failure; C. explain why bolt failure may be avoided by routine and...
emo
Views: 80
Replies: 0
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Topic started 18 Jan 2012 17:47 by anandgardener
Crankshaft deflections taken from a large slow speed engine show an apparent alignment problem. A. (i) Describe the investigation to find the actual degree of misalignment. (ii) State FOUR possible causes of the misalignment. B. State the influence of changes of hull loading, seawater temperature...
emo
Views: 81
Replies: 0
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Topic started 18 Jan 2012 17:40 by anandgardener
With reference to electrical switch gear explain the purpose of each of the following: (a) Preferential tripping, (b) Dash pots. (c) Reverse power tripping; (d) Under voltage tripping.
emo
Views: 93
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:40 by anandgardener
Draw a skeleton diagram of connections showing how to protect an alternator against overload, leakage and internal short circuit.
emo
Views: 77
Replies: 0
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Topic started 18 Jan 2012 17:39 by anandgardener
Describe the principle of operation of the synchronous induction motor. Explain in detail what occurs when the motor is started up and pulls into synchronism.
emo
Views: 80
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:38 by anandgardener
Define the term "valence electron" and explain, in terms of electronic structure, why some substances are better conductors of electricity than others.
emo
Views: 88
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:38 by anandgardener
A single-phase alternator has a resistance voltage drop of 3 per cent and a leakage reactance voltage drop of 20 per cent on full load. The armature reaction ampere-turns are 40 per cent of the resultant field ampere-turns. Determine the regulation at full-load current and – (a) Unity power-factor...
emo
Views: 86
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:38 by anandgardener
A 20KVA, 2000/200V, single-phase transformer has a primary resistance of 2.1 and a secondary resistance of 0.026 . The corresponding leakage reactance are 2.5 and 0.03 . Estimate the regulation at full load under power-factor condition of (a) unity (b) 0.5(lagging) and (c) 0.5 (Leading)...
emo
Views: 81
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:37 by anandgardener
A certain transistor has a common-emitter short-circuit current gain  or  = 50. Calculate the common-base short- circuit current gain.
emo
Views: 86
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:37 by anandgardener
The supplies are from a ship's electrical system, which has two identical three-phase, star-connected alternators operating in parallel. The machines share a total load of 1000kW at 440V, 0.8 (lagging) power factor. If the kW loading of the two machines are equal and one machine supplies a lagging...
emo
Views: 70
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:12 by anandgardener
(a) With reference to limiting voltage dip and response time under impact loading: (i)State the effect of suddenly connecting a large increasing load across a ship's electrical power system, (ii) State the problems associated in obviating this effect, (b) Sketch a simple arrangement of a brushless...
emo
Views: 106
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:11 by anandgardener
Why is plain overload protection insufficient in the case of large alternator?
emo
Views: 112
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:11 by anandgardener
Describe in detail the operations for starting a large sixteen-pole, 50-c/s, three-phase synchronous motor using an auxiliary starting motor.
emo
Views: 106
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:11 by anandgardener
Explain what is meant by, and the significance of, four of the following terms (i) voltage stabilisation, (ii) filter choke, (iii) impedance, (iv) rectification, (v) grid bias voltage.
emo
Views: 93
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:10 by anandgardener
Draw a typical open-circuit magnetisation curve for a turbo-alternator, and explain how the zero power-factor characteristic can be obtained, if the only loading apparatus available consists of a large oil-immersed, iron-cored reactor of fixed inductance. Show how the effects of armature reaction...
emo
Views: 81
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:10 by anandgardener
In a certain transistor, a change in emitter current of 1mA produced a change in base current of 0.1mA. Calculate the common-emitter and common-base short-circuit current gains.
emo
Views: 94
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:09 by anandgardener
Two 3.3kV, star-connected alternators when operating in parallel supply the following loads; (a) 800kW at unity power factor, (b) 600kW at a power factor of 0.707 (lagging). The current of one machine is 150A at a power factor of 0.85 (lagging). Find the current, output and power factor of the...
emo
Views: 71
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:09 by anandgardener
A 500V, six-pole, 50Hz, three-phase induction motor develops 20kW inclusive of mechanical losses, when running at 990 rev/min, the power factor being 0.85 (lagging). Calculate, (a) The percentage slip, (b) The frequency of the rotor e.m.f., (c) The rotor copper loss, (d) The input to the motor...
emo
Views: 69
Replies: 0
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anandgardener's Avatar
Topic started 18 Jan 2012 17:08 by anandgardener
Find the no-load terminal voltage of a three-phase, four- pole a.c. generator from the following data. Flux per pole (assumed sinusoidally distributed) = 0.14 webers. Slots per pole per phase = 2. Conductors per slot = 2. Assume a Distribution Factor of 0.966. The machine is driven at 1500 rev/min...
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