1
GATE EE 2007
+2
-0.6
A single-phase $$50$$ $$kVA,$$ $$250$$ $$V/500V$$ two winding transformer has an efficiency of $$95\%$$ at full load, unity power factor. If it is reconfigured as a $$500V/750V$$ auto-transformer, its efficiency at its new rated load at unity power factor will be
A
$$95.752\%$$
B
$$97.851\%$$
C
$$98.276\%$$
D
$$99.241\%$$
2
GATE EE 2006
+2
-0.6
A $$300$$ $$kVA$$ transformer has $$95\%$$ efficiency at full load $$0.8$$ $$pf$$ lagging and $$96\%$$ efficiency at half load, unity $$pf.$$

The iron loss $$\left( {{P_i}} \right)$$ in $$kW,$$ under full load operation are

A
$${P_c} = 4.12,\,\,{P_i} = 8.51$$
B
$${P_c} = 6.59,\,\,{P_i} = 9.21$$
C
$${P_c} = 8.51,\,\,{P_i} = 4.12$$
D
$${P_c} = 12.72,\,\,{P_i} = 3.07$$
3
GATE EE 2006
+2
-0.6
Two transformers are to be operated in parallel such that they share load in proportion to their $$kVA$$ ratings. The rating of the first transformer is $$500$$ $$kVA$$ and its $$pu$$ leakage impedance is $$0.05$$ $$pu.$$ If the rating of second transformer is $$250$$ $$kVA,$$ its $$pu$$ leakage impedance is
A
$$0.20$$
B
$$0.10$$
C
$$0.25$$
D
$$0.025$$
4
GATE EE 2006
+2
-0.6
A $$300$$ $$kVA$$ transformer has $$95\%$$ efficiency at full load $$0.8$$ $$pf$$ lagging and $$96\%$$ efficiency at half load, unity $$pf.$$

What is the maximum efficiency (in %) at unity $$pf$$ load?

A
$$95.1$$
B
$$96.2$$
C
$$96.4$$
D
$$98.1$$
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