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Q3. Discuss magnetic leakage in a Transformer, and indicate how its value may be kept down, show, by means of a vector diagram, how the voltage regulation of a transformer is influenced by its magnetic leakage.

Q4. A. Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests?

B. What is meant by equivalent resistance?

Q3. With respect to power transformers kindly explain the following protections

1. Overload protection 2. Overcurrent protection for phase faults 3. Earth Fault protection 4. Differential protection 5. Directional protection

Q3. A. Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests? (8)

B. What is meant by equivalent resistance? (4)

C. What is meant by all day transformer efficiency? (4)

Q5. a) The current transformer (CT) and potential transformer (PT) or voltage transformer are both measuring devices. List their shipboard application. (6)

b) Sketch and describe any one type of current transformer. (10)

Q1. a) What are the effects of voltage and frequency changes on transformer functioning? (8)

b) State the various energy losses in transformers. (8)

Q3. a) Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests? (12)
b) What is meant by equivalent resistance. (4)

Q3. A. Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests? (10)

B. What is meant by equivalent resistance? (6)

Q6. With Reference to 3-phase Transformers:

a) Discuss the essential and desirable conditions to be fulfil for operating two three-phase transformers in parallel. (5)

b) What are the advantages of transformer bank of three 1-phase transformers over a unit three phase transformer of the same kVA rating? (5)

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 (6)

Q4. (a) Explain the principle of a Transformer? Discuss the various types of transformers used onboard? (8)

(b) In a container ship, a 3-ph, delta/delta connected 6600/440 V, 60 Hz transformer is feeding AMP supply from shore to 440 Volt switchboard. Transformer primary current takes a line current of 100 amp, when secondary load of 0.8 lagging p.f. is connected. Determine each coil-current and KW output of transformer. (8)

Q5. A) With reference to large electrical transformers on board ships:

a) State where these transformers may be used (2)

b) State a typical efficiency range for a transformer (2)

c) State the protective devices that are fitted (2)

d) Describe the maintenance requirements (2)

B) What are the losses in transformers? Mention the various factors which affect these losses. In a 25KVA, 3300/223 V, Single phase transformer, the iron and full load Cu. Losses are respectively 350 and 400 watts. Calculate the efficiency at half-full load, 0.8 power factor (8)