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a. With a neat diagram, describe the Sumpner’s method of testing transformers. How
can the voltage regulation be predetermined using this test? (5)
b. ۸ 3 step down transformer is connected to 6.6 kV supply mains and takes 80A.
Calculate its secondary line voltage and line current for the following connections if
the ratio of turns per phase is 16 (i) Y-Y (ii) Y- A (iii) A— ४ (iv) ७ - 6. (5)
a. Derive expression for saving in copper effected by using an autotransformer instead
of a two winding transformer. (5)
b. A load of 6 kW is supplied by an autotransformer at 120 V and upf. If the primary
voltage is 240 V, determine (i) transformation ratio (ii) secondary current (iii) primary

current (iv) number of secondary turns if the total number of turns is 280 (v) power

transformed and (vi) power conducted directly from supply mains to load. (5)

a. Explain with neat circuit diagram and phasors, how a 2-phase supply can be

obtained from a 3-phase supply. (5)

b. Explain the vector groupings Yy0, 1200, ४१1, 1991, Yd11 and Dy11 in three phase

transformers. (5)
मं मं मत मंद

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