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Electrical Engineering Objective Questions { Transformers }

295.  If a saw-cut is made in the iron core of a single phase transformer as shown in the givng figure, with secondary terminals open, it will result in
A. no voltage across secondary terminals due to discontinuity in magnetic circuit
B. excessively large current drawn by primary
C. no appreciable change in the operation of the transformer
D. no transformer action and the primary current will be greatly reduced.
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296. If the height to width ratio of the window of coretype transformer ii increased, then
A. its leakage reactance and percentage voltage regulation will decrease
B. its leakage reactance and percentage voltage regulation will increase
C. its leakage reactance will be unaffected but total space in the window will increase to accommodate the windings better
D. efficiency will increase and temperature rise will decrease
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297.  If the secondary winding ofthe ideal transformer of the circuit shown in the given figure has 40 turns, then for maximum power transfer to the 2-ohm resistor, the number of turns required in the primary winding will be Ideal Transformer
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298.  A 220/110V, 50 Hz single-phase transformer having a negligible winding resistances operates from a variable voltage, variable frequency supply such that Vi/f (V1 = primary applied voltage, f = source frequency) is constant. This will bring in, in the given range of frequencies.
A. variation in both eddy current loss and hysteresis loss
B. variation only in the eddy current loss, hysteresis loss remaining constant
C. variation only in the hysteresis loss, eddy current loss remaining constant
D. no change either in the eddy current loss or the hysteresis loss
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299.  In a 3-phase power transformer, 5-limbed construction is adopted to
A. suppress the 5th and 7th harmonics
B. supress the 3rd and its multiple harmonics
C. suppress all the orders of harmonics
D. increase the capacity of the transformer
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300.  A transformer has a resistance of2% and reactance of 4%. Its regulations at 0.8 power factor lagging a leading respectively are
A. 4 per cent and 0.8 per cent Re2
B. -4 per cent and 0.8 per cent
C. -0.8 per cent and 4 per cent
D. 0.8 per cent and -4 per cent
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301.  Consider the following statements : The use of Delta-connected tertiary winding in star-star connected power transformers I. makes available supply for single-phase loads.2. suppresses harmonic voltages. 3. allows flow of earth fault current for operation of protective devices 4. provides low-reactance paths for zero-sequence currents.Of the statements :
A. 1, 2 and 3 are correct
B. 1,3 and 4 are correct
C. 2 and 4 are correct
D. 1, 2, 3 and 4 are correct
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