MCQs of Transformers (Electrical Machine - I - 3140913)

Electrical Machine - I (3140913) MCQs

MCQs of Transformers

Showing 111 to 120 out of 155 Questions

111.

Two single-phase transformers A and B are operating in parallel with the same pu impedance and different x/r ratios (Xa > Xb). Then

(a)	A pf < B pf
(b)	B pf < A pf
(c)	A pf = B pf
(d)	A pf = B pf = Load pf

112.

Two single-phase transformers A and B are operating in parallel with the different pu impedance (Za > Zb) and identical x/r ratios (Xa = Xb). Then

(a)	Za/Zb = Sb/Sa
(b)	Za/Zb = Sa/Sb
(c)	Za/Zb = 1
(d)	Za/Zb = (Sb/Sa)²

113.

Two single-phase transformers A and B are operating in parallel with the different pu impedance (Za ≠ Zb) and identical x/r ratios (Xa = Xb), both sharing a load of Sl. Then the load shared by transformer B is

(a)	$S_{b} = \frac{Z_{b}}{(Z_{a} + Z_{b})} \times S_{L}$
(b)	$S_{b} = \frac{Z_{a}}{(Z_{a} + Z_{b})} \times S_{L}$
(c)	$S_{b} = \frac{Z a \times Z_{b}}{(Z_{a} + Z_{b})} \times S_{L}$
(d)	$S_{b} = \frac{Z a}{(Z_{a} - Z_{b})} \times S_{L}$

114.

Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 2 and 4 are operating in parallel. Transformer A will be running over-load by ....... percent.

(a)	20
(b)	66.66
(c)	33.33
(d)	40

115.

The secondary winding of an auto transformer is also called

(a)	Compensating winding
(b)	Common winding
(c)	Tertiary winding
(d)	Damping winding

116.

The kVA rating of an ordinary 2-winding transformer is increased when connected as an autotransformer because

(a)	transformation ratio is increased
(b)	secondary voltage is increased
(c)	energy is transferred both inductively and conductivity
(d)	secondary current is increased

117.

Which of the following points is the disadvantage of auto transformers?

(a)	Weight of conductor reduces
(b)	Ohmic losses reduce
(c)	Leakage reactance reduces
(d)	Lower short-circuit current

118.

An auto-transformer is supplied with a load of 8 kW, 115 V, and a unity power factor. If the primary voltage is 345 V, calculate the power transferred to the inductive.

(a)	5.33 kW
(b)	5.64 kW
(c)	7.80 kW
(d)	none of these

119.

An autotransformer having a transformation ratio of 0.8 supplies a load of 3 kW. The power transferred conductively from primary to secondary is.......kW.

(a)	0.6
(b)	2.4
(c)	1.5
(d)	0.27

120.

The saving in Cu achieved by converting a 2-winding transformer into an auto transformer is determined by

(a)	voltage transformation ratio (K)
(b)	load on the secondary
(c)	magnetic quality of core material
(d)	size of the transformer core

Showing 111 to 120 out of 155 Questions