246. The value of useful flux least depends on
A. load
B. magnetomotive force
C. voltage
D. all of the above
247. In which of the following trail' irmer part of primary winding also serves as the secondary winding?
A. Potential transformer
B. Auto transformer
C. Step-up transformer
D. Current transformer
248. Which of the following canbe reduced when the flux density in the transformer core is increased?
A. Copper losses
B. Output frequency
C. Size of the transformer
D. None of the above
249. Burden of a current transformer is usually expressed in
A. amperes
B. volts
C. volt amperes
D. kilowatt
250. Current transformers for meters and relays usually have
A. 1 : 2 ratio
B. 5 : I ratio
C. 5-A secondaries
D. 15-A secondaries
251. All day efficiency is the ratio of output to input in
A. kVA at a particular instant
B. kW at particular instant
C. kVARh at praticular instant
D. kWh during 24 hours
252. While performing back-to-back test, the amount of power consumed is equal to
A. iron and copper losses of two transformers at full load
B. full load rated output of the two transformers
C. rated output of two transformersand iron and copper losses of transformers at full load
D. none of the above
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