Electrical Machines Questions and Answers – Transformer Construction

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This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Transformer Construction”.

1. The primary and secondary of a transformer are ________ coupled but _______ connected.
a) magnetically, not electrically
b) electrically, not magnetically
c) magnetically, also magnetically
d) electrically, also electrically
View Answer

Answer: a
Explanation: Transformer is the machine which has physical spacing and has magnetic circuit to exchange the voltage.
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2. We can employ transformers for a power range of _________
a) lower and higer values
b) lower values
c) higher values
d) medium values
View Answer

Answer: a
Explanation: A transformer can be put in use upto a varying range of the power and it is usually available in readily in market.

3. A transformer has comparitively much higher efficiency than a similar induction machine due to _________
a) small air gaps
b) no moving parts
c) strong coupling
d) all of the mentioned
View Answer

Answer: d
Explanation: Transformer does not has any moving components so losses are anyway reduced and also the coupling is very strong between two sides.
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4. It was needed that to isolate dc noise coming from the transmitted signal, to attain the same which machine can be used without suffering significant loss?
a) transformer
b) dc machine
c) induction machine
d) stepper motor
View Answer

Answer: a
Explanation: We should use transformer to achive the isolation of dc.

5. Which is the most widely used material in the core of the transformer?
a) cold rolled grain oriented sheet steel
b) cold rolled grain steel
c) soft iron
d) steel
View Answer

Answer: a
Explanation: CRGO has magnetization in the rolling direction and low core losses and very high permeability than present materials.
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6. The leakage flux is the flux in side the transformer which?
a) links either of the windings
b) links both of the windings
c) yoke of the core
d) windows of the core
View Answer

Answer: a
Explanation: Leakage flux is meant to to be loss as it does not link two windings.

7. It is advised that staggering of the butt joints _________
a) reduces reluctance of the path
b) increases air gap
c) increases mechanical strength
d) all of the mentioned
View Answer

Answer: c
Explanation: Staggering is done for the steel butt joints of the transformer to gain more mechanical strength as the continuous air gap reduces the same.
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8. Consider two transformers X and Y having exact ratings, but have flux densities of 1.5T and 2T respectively. The weight of the transformer A per KVA will be _________
a) more than that of B
b) lesser than that of B
c) equal to that of B
d) can not be said from the given data
View Answer

Answer: a
Explanation: Flux density = flux/Area.
Hence A has more area than B and so weight of A will be more than that of B.

9. Consider two transformers X and Y having identical ratings, but have flux densities of 1.5T and 2T respectively. The weight of the transformer B per KVA will be _________
a) more than that of A
b) lesser than that of A
c) equal to that of A
d) can not be said from the given data
View Answer

Answer: b
Explanation: Flux density = flux/Area.
Hence A has more area than B and so weight of B will be less than that of A.
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10. Transformers do not require any type of cooling as it well ventilated.
a) True
b) False
View Answer

Answer: b
Explanation: It is wrong to say that transformers do not need any cooling. It does need various types of cooling like oil cooling, air cooled etc.

11. A coupling magnetic field inside a rotating machine or static machine like transformers must involve with _________
a) mechanical parts
b) electrical parts
c) both electrical and mechanical
d) either of the electrical or mechanical parts
View Answer

Answer: a
Explanation: The coupling field should interact with both the electrical as well as mechanical parts in order to achieve electromechanical energy conversion.

12. A coupling magnetic field inside a rotating machine or static machine like transformers must involve with _________

I. electrical system to extract energy from electrical system.
II. mechanical system to extract energy from electrical system.

a) Only I is true
b) Only II is true
c) I and II are true
d) I and II are false
View Answer

Answer: b
Explanation: The energy conversion which involves both electrical as well as mechanical systems must have mutual field.

13. I. Pulse transformers use soft ferrites.
II. The transformers used in the radio recievers use air core.
a) Only I is true
b) Only II is true
c) I and II are true
d) I and II are false
View Answer

Answer: c
Explanation: Pulse transformers are used in isolation transformer and need high permeablity.

14. Stepping of the core is implemented in the core to _________
a) reduce conductor material and copper losses
b) reduce core loss
c) to provide mechanical strength
d) to reduce magnetizing current
View Answer

Answer: a
Explanation: Stepping of the core is done so that the copper material reduces.

15. Core type transformers have, LV and HV windings are arranged such that _________
a) Half LV near the core and half HV outside LV on each limb
b) LV one one limb and HV on the other
c) Half LV outside the core and half HV inside LV on each limb
d) LV and HV windings are sandwiched
View Answer

Answer: a
Explanation: Core windng has first of all both the windings on the same limb and HV is placed outside to have tappings to the transformer.

16. The shell type transformers have, LV and HV windings are arranged such that _________
a) Half LV near the core and half HV outside LV on each limb
b) LV one one limb and HV on the other
c) Half LV outside the core and half HV inside LV on each limb
d) LV and HV windings are sandwiched
View Answer

Answer: d
Explanation: Shell type windng has mix of LV and HV winding sandwiched over each other.

Sanfoundry Global Education & Learning Series – Electrical Machines.

To practice all areas of Electrical Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.

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