302. The equivalent resistance andequivalent reactance of a transformer are respectively 0.5 SI and 0.8 12. The voltage regulation will be zero when the load power factor is

A.0.8lagging 0.5

B. 707 lagging05

C.leading 0.8

D. r leading 1/0.89

303. A symmetrical 3-phase supply is applied to theprimary terminals A1, B and C1 of the Y-Y transformer asshown in the given figure. The secondary terminals A2, B2 and C2 give a symmetrical 3-phase voltage. If the terminals H1 and H2 of phase I of the primary are reversed without changing the supply at A1, B1 and C1, thenthe phase angle between the line voltage VA2B2 and c2A2 on the secondary side will be

A. 180?

B.120

C. 60?

D. 30?

304. For the system shown in given figure, the phase relation of current 'I' with respect to the voltage VAB is Ideal transformer

A. zero

B. 90? lead

C. 90? lag

D. 180?

305. A 3-phase Y/A transformer has per phase turn ratio 'K' and line voltage ratio `K1'. If the voltage of A winding lags the voltage of Y winding by an angle 4), then K, K1 and (pare related as

A. K1 = K and 4) = -30?

B. K1 = ?17 and = -30?

C. K1 = %R. K and (1) = -30?

D. K1 = JK and (1) = -30?

306. Two transformers X and Y with identical ratings and dimensions have 0.8 mm and 1.2 mm thick laminations respectively. If Rm and Xm are the magnetizing branch parameters in the equivalent circuit, then

A. Rin values in both are likely to be equal, but Xm of X is likely to be higher than Xm of Y Pure inductive load

B.Xm values in both are likely to be equal, but Rm of X is likely to be higher than Rm of Y

C. Xm values in both are likely to be equal, but Rm of X is likely to be lower than Rm of Y

D. Rm values in both are likely to be equal, but Xm of X is likely to be lower than Xm of Y

307. Hysteresis loss of a transformer designed at voltage 'V' and frequency 'f' is Ph. If the transformer is operated from a voltage `x?/' and frequency `xf' the hysteresis loss for a Steinmetz constant of 2 will be

A. x2Ph

B. xPh

C. Ph

D. X3Ph

308. Three single-phase transformers, each of 100 kVA rating are connected in delta. If one of the transformers is taken out of service, the capacity of the system will be

A. 200 kVA

B. 173.2 kVA

C. 115.5 kVA

D. 36.6 kVA

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