Test: Transformer of Electrical Machines

# Test: Transformer of Electrical Machines

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## 10 Questions MCQ Test GATE Electrical Engineering (EE) 2023 Mock Test Series | Test: Transformer of Electrical Machines

Test: Transformer of Electrical Machines for Electrical Engineering (EE) 2023 is part of GATE Electrical Engineering (EE) 2023 Mock Test Series preparation. The Test: Transformer of Electrical Machines questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Transformer of Electrical Machines MCQs are made for Electrical Engineering (EE) 2023 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Transformer of Electrical Machines below.
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Test: Transformer of Electrical Machines - Question 1

### Which of the following is not true relating to an ideal transformer?

Detailed Solution for Test: Transformer of Electrical Machines - Question 1

In an ideal transformer there is no-loss (either in winding or core). The leakage reactance is also zero (as no-voltage drop).
Magnetizing current is zero due to infinite permeability of core.

Test: Transformer of Electrical Machines - Question 2

### The emf per turn of a single phase 10 kVA, 2200/220 V, 50 Hz transformer is 10 V. The net cross-sectional area of core for a maximum flux density of 1.5 T is

Detailed Solution for Test: Transformer of Electrical Machines - Question 2

Maximum flux,

∴ New cross-sectional area of core,

Test: Transformer of Electrical Machines - Question 3

### A 1 kVA, 400 Hz transformer is desired to be used at a frequency of 60 Hz. The kVA rating of the transformer at this reduced frequency is

Detailed Solution for Test: Transformer of Electrical Machines - Question 3

kVA rating of transformer,
or,
Since V ∝ f, therefore, S ∝ f
∴

Test: Transformer of Electrical Machines - Question 4

A 2200 / 250 V transformer takes 0.5 A at a p.f. of 0.3 on open-circuit. The magnetising component of no-load primary current is

Detailed Solution for Test: Transformer of Electrical Machines - Question 4

Test: Transformer of Electrical Machines - Question 5

A 50 MVA, 76.2/33 kV, 1-φ, 50 Hz, two-winding transformer with tap changer has percentage impedance of (0.5 + j7.0). What tapping must be used to maintain rated voltage at the secondary on full load at 0.8 lagging power factor?

Detailed Solution for Test: Transformer of Electrical Machines - Question 5

Hence, voltage to be raised, for maintaining rated voltage = 4.6%.
Thus, tap setting required on the HV side = -4.6% or 4.6 % down.

Test: Transformer of Electrical Machines - Question 6

The ohmic drop of a transformer is 1% while the reactance drop is 5% of the voltage. The regulation of the transformer at 0.8 power factor leading and 0.8 power factor lagging are respectively

Detailed Solution for Test: Transformer of Electrical Machines - Question 6

Test: Transformer of Electrical Machines - Question 7

A 1 kV, 50 Hz supply to a transformer results in 650 W hysteresis loss and 400 W eddy current loss. If both the applied voltage and frequency are doubled, the new core loss would be

Detailed Solution for Test: Transformer of Electrical Machines - Question 7

Test: Transformer of Electrical Machines - Question 8

A transformer designed for operation of 60 Hz supply is working on 50 Hz supply system without changing its voltage and current ratings. When compared with full-load efficiency at 60 Hz, the transformer efficiency on full load at 50 Hz will

Detailed Solution for Test: Transformer of Electrical Machines - Question 8

We know that, eddy current loss  and hysteresis loss,

When V - constant, Pe = constant
and
When frequency is increased from 50 Hz to 60 Hz, Ph will increase. Thus, core loss will increase marginally, therefore efficiency will decrease marginally.

Test: Transformer of Electrical Machines - Question 9

For a core-type power transformers, both primary and secondary windings have circular coil sections, because this section

Detailed Solution for Test: Transformer of Electrical Machines - Question 9

Primary and secondary windings of a core type transformer have circular coil section to reduce the mean length of each turn so that it require minimum conductor material and thus have less copper loss which will increase the efficiency.

Test: Transformer of Electrical Machines - Question 10

A 10 kVA, 400 V/ 200 V, 1 -phase transformer with a percentage resistance of 3% and percentage reactance of 6% is supplying a current of 50 A to a resistive load. The value of the load voltage is

Detailed Solution for Test: Transformer of Electrical Machines - Question 10

Hence, load voltage = 194 volt

## GATE Electrical Engineering (EE) 2023 Mock Test Series

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## GATE Electrical Engineering (EE) 2023 Mock Test Series

22 docs|274 tests