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ESE EE : Electrical Machines Champion Quiz 2

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Question 1

A two-winding transformer is converted into an auto-transformer. If we apply additive polarity and subtractive polarity for the connections, then the secondary voltage is 2640 V and 2160 V, respectively. What is the ratio of primary to secondary voltage of the original transformer?

Question 2

A starting torque of 80 Nm is developed in an induction motor by an auto-transformer starter with a tapping of 30%. If the tapping of auto-transformer starter is 60%, then what is the starting torque?

Question 3

A single-phase, 10 kVA, 2000/200 V, 50 Hz transformer is connected to form an autotransformer as shown in the figure given below. What are the values of V₁ and I₂, respectively?

Question 4

The ratio of primary/secondary voltages in a step-down transformer is 2:1. The saving in terms of weight of copper required if an autotransformer is used instead of a two-winding transformer will be

Question 5

Match List-I with List-II and select the correct answer using the code given below the lists:
List-I
A) magnetic flux
B) Magneto motive force
C) Reluctance
D) Permeability
List-II
1) Resistance
2) Electric current
3) Conductivity
4) Electromotive force

Question 6

A magnetic circuit has 150 turns-coil, the cross-sectional area and the length of the magnetic circuit What are the values of magnetic field intensity and relative permeability when the current is 2 A and total flux is 0.3*10^-3 ?

Question 7

The emf induced in a conductor of machine driven at 600 rpm, the peak value of flux density is 1.0 Wb/m², diameter of machine 2.0 meter and length of machine 0.30 m is

Question 8

Neglecting losses, if the power transformed inductively is equal to power transformed conductively in an auto-transformer, then the secondary to primary ratio of transformer is

Question 9

What is the power transferred conductively from primary to secondary of an auto-transformer having trans-formation ratio of 0.8 supplying a load of 3 kW?

Question 10

A two winding 220 V/1 10 V, 1.5 kVA transformer is reconnected as a 220/330 V autotransformer. It is re-rated as

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ESE & GATE EE Electrical Machines

Jul 5ESE & GATE EE