Why not reduce the noise in the core by reducing the amount of flux?

Why not reduce the noise in the core by reducing the amount of flux?
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1 Answer

Answer :

Transformer voltages are fixed by system requirements. The ratio of these voltages to the number of turns in the winding determines the amount of magnetization. This ratio of voltage to turns is determined mainly for economical soundness. Therefore the amount of flux at the normal voltage is fixed. This also fixes the level of noise and vibration.
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Related questions

[53] The iron loss of the transformer is negligible during short circuit test because A. The entire input is just sufficient to meet Cu losses only B. Flux produced is a small fraction of the normal flux C. Iron core becomes fully saturated D. Supply frequency is held constant

Description : [53] The iron loss of the transformer is negligible during short circuit test because A. The entire input is just sufficient to meet Cu losses only B. Flux produced is a small fraction of the normal flux C. Iron core becomes fully saturated D. Supply frequency is held constant

Last Answer : B. Flux produced is a small fraction of the normal flux

[31] With both S1 and S2 open, the core flux waveform will be [GATE 2009] A. a sinusoidal at fundamental frequency B. flat-topped with third harmonic C. peaky with third-harmonic D. none of these

Description : [31] With both S1 and S2 open, the core flux waveform will be [GATE 2009] A. a sinusoidal at fundamental frequency B. flat-topped with third harmonic C. peaky with third-harmonic D. none of these

Last Answer : B. Flat topped with third harmonic

27] In a transformer, the leakage flux of each winding is proportional to the current in that winding because A. Ohm's law applies to magnetic circuits B. Leakage paths do no saturate C. the two windings are electrically isolated D. mutual flux is confined to the core

Description : 27] In a transformer, the leakage flux of each winding is proportional to the current in that winding because A. Ohm's law applies to magnetic circuits B. Leakage paths do no saturate C. the two windings are electrically isolated D. mutual flux is confined to the core

Last Answer : B. Leakage path do not saturate

12] Which is not the basic element of the transformer? A. core B. primary winding C. secondary winding D. mutual flux

Description : 12] Which is not the basic element of the transformer? A. core B. primary winding C. secondary winding D. mutual flux

Last Answer : D. Mutual flux

45 The function of conservator in a transformer is A. To protect against internal fault B. To reduce copper as well as core losses C. To cool the transformer oil D. To take care of the expansion and contraction of transformer oil due to variation of temperature of surroundings

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Last Answer : D. To take care of the expansion and contraction of transformer oil due to variation of temperature of surroundings

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Description : 43 The purpose of providing an iron core in a transformer is to A.Provide support to windings B. Reduce hysteresis loss C. decrease the reluctance of the magnetic path D. reduce eddy current losses

Last Answer : C. Decrease the reluctance of the magnetic path

8 The transformer core is laminated to A. Reduce the copper losses B. Reduce the core losses C. Reduce the eddy current losses D. None of the above

Description : 8 The transformer core is laminated to A. Reduce the copper losses B. Reduce the core losses C. Reduce the eddy current losses D. None of the above

Last Answer : C. Reduce the eddy current losses

What are the factors affecting the selection of Maximum flux density?

Description : What are the factors affecting the selection of Maximum flux density?

Last Answer : 1. Net core weight: Higher the flux density lesser net weight of core. 2.Saving in copper:Higher the flux density lesser mean turn of windings. 3.Overall economy: Higher the flux ... High Flux density results in high losses and hence efficiency decreases 8.Hence high temperature rise and noise

What is the cause of noise in transformer?

Description : What is the cause of noise in transformer?

Last Answer : The cause of noise in the transformer is mainly because of magnetostriction effect and also loosening of stampings and mechanical forces produced during working.

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Description : The area of the yoke in a transformer is taken 15 to 20% larger than that of the core. Why?

Last Answer : By keeping yoke area 15-20% higher ,the flux density in the yoke is reduced, resulting into reduction in iron losses for yoke. The reduced core area results working flux density and needed to increase the number of turns.

In transformers, why the low voltage winding is placed near the core?

Description : In transformers, why the low voltage winding is placed near the core?

Last Answer : The winding & Core are both made of metals and so an insulation have to be placed in between them, the thickness of insulation depends on the voltage rating of the winding. In order to reduce the insulation requirement the low voltage winding place near the core.

Why the cross-section of iron is less than total cross section area of core?

Description : Why the cross-section of iron is less than total cross section area of core?

Last Answer : This is because the core is laminated & on each lamination the insulations are are used.

Explain on the material used for core construction?

Description : Explain on the material used for core construction?

Last Answer : A:The core is constructed by sheet steel laminations assembled to provide a continuous magnetic path with minimum of air gap included. The steel used is of high ... The thickness of lamination varies from 0.35mm for a frequency of 50Hz and 0.5mm for a frequency of 25Hz.

What is the purpose of laminating the core in a transformer?

Description : What is the purpose of laminating the core in a transformer?

Last Answer : In order to minimize eddy current loss.

Where is core type and shell type construction suitable for a transformer?

Description : Where is core type and shell type construction suitable for a transformer?

Last Answer : Core type transformers are popular in High voltage applications like Distribution transformers, Power transformers, and obviously auto transformers. Where as, Shell type transformers are ... voltage applications like transformers used in electronic circuits and power electronic converters etc

What are the advantages of shell type transformer over core type transformers?

Description : What are the advantages of shell type transformer over core type transformers?

Last Answer : In shell type transformers the coils are well supported on the all sides and so they can withstand higher mechanical stresses developed during short circuit conditions. Also the leakage reactance will be less in shell type transformers.

A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts

Description : A shading coil used in an AC magnetic controller, functions to _____________. A. reduce vibration and noise in the contactor B. prevent flux buildup in the operating coil C. eliminate arcing when the contacts close D. energize the operating coil and 'pull in' the contacts

Last Answer : Answer: A

68 The path of a magnetic flux in a transformer should have A. High resistance B. High reluctance C. Low resistance D. Low reluctance

Description : 68 The path of a magnetic flux in a transformer should have A. High resistance B. High reluctance C. Low resistance D. Low reluctance

Last Answer : D. Low reluctance

38] In a transformer the energy is conveyed from primary to secondary? A. Through cooling coil B. Through air C. By the flux D. None of the above

Description : 38] In a transformer the energy is conveyed from primary to secondary? A. Through cooling coil B. Through air C. By the flux D. None of the above

Last Answer : C. By the flux

6 The value of flux involved in the emf equation of a transformer is A. rms value B. rms value C. Maximum value D. Instantaneous value

Description : 6 The value of flux involved in the emf equation of a transformer is A. rms value B. rms value C. Maximum value D. Instantaneous value

Last Answer : C) maximum value

Greater the secondary leakage flux?

Last Answer : Greater the secondary leakage flux less will be the secondary induced e.m.f.

The use of higher flux density in the transformer design?

Last Answer : The use of higher flux density in the transformer design reduces weight per kVA.

The leakage flux in a transformer depends upon?

Last Answer : The leakage flux in a transformer depends upon load current.

The value of flux involved in the e.m.f. equation of a transformer is ?

Last Answer : Power on primary and secondary side of transformer A. Remains Approximately constant B. Are always different C. Is always 100kVA D. None of these

The path of magnetic flux in a transformer should have?

Description : The path of magnetic flux in a transformer should have?

Last Answer : The path of magnetic flux in a transformer should have low reluctance.

Reversing the current flow through a coil will ___________. A. reduce the amount of flux produced B. have no effect on the eddy currents produced C. reduce the power consumed D. reverse its two-pole field

Description : Reversing the current flow through a coil will ___________. A. reduce the amount of flux produced B. have no effect on the eddy currents produced C. reduce the power consumed D. reverse its two-pole field

Last Answer : Answer: D

69 In case there are burrs on the edges of the laminations of the transformer, it is likely to result in A. Vibrations B. Noise C. Higher eddy currents loss D. Higher hysteresis loss

Description : 69 In case there are burrs on the edges of the laminations of the transformer, it is likely to result in A. Vibrations B. Noise C. Higher eddy currents loss D. Higher hysteresis loss

Last Answer : C. Higher eddy currents loss

60)The noise resulting from vibrations of laminations set by magnetic force, is termed as A. magnetostriction B. boo C. hum D. zoom

Description : 60)The noise resulting from vibrations of laminations set by magnetic force, is termed as A. magnetostriction B. boo C. hum D. zoom

Last Answer : C. Hum

Noise level test in a transformer is a?

Last Answer : Noise level test in a transformer is a type test.

The noise produced by a transformer is termed as?

Description : The noise produced by a transformer is termed as?

Last Answer : The noise produced by a transformer is termed as hum.

what are the causes of noise in transformer?

Last Answer : Transformer noise is generated due to vibration of core and winding this is because of magnetostriction and magnetomotive force.

[75] Two transformers are connected in parallel. These transformers do not have equal percentage impedance which results A. Short-circuiting of the secondaries B. Power factor of one of the transformers is leading while that of the other lagging C. Transformers having higher copper losses will have negligible core losses D. Loading of the transformers not in proportion to their kVA ratings.

Description : [75] Two transformers are connected in parallel. These transformers do not have equal percentage impedance which results A. Short-circuiting of the secondaries B. Power factor of one of the ... have negligible core losses D. Loading of the transformers not in proportion to their kVA ratings.

Last Answer : D. Loading of the transformers not in proportion to their kVA ratings

72 Harmonics in transformer result in A. Increased core losses B. Increased I2R losses C. Magnetic interference with communication circuits D. All of the above

Description : 72 Harmonics in transformer result in A. Increased core losses B. Increased I2R losses C. Magnetic interference with communication circuits D. All of the above

Last Answer : D. All of the above

49 The open circuit test is carried out in a transformer to find the A. Cu loss B. Core loss C. Total loss D. Insulation resistance

Description : 49 The open circuit test is carried out in a transformer to find the A. Cu loss B. Core loss C. Total loss D. Insulation resistance

Last Answer : B. Core loss

46 The core used in high frequency transformer is usually A. Copper core B. Cost iron core C. Air core D.Mid steel core

Description : 46 The core used in high frequency transformer is usually A. Copper core B. Cost iron core C. Air core D.Mid steel core

Last Answer : C. Air core

19 .Transformer cores are built up from laminations rather than from solid metal so that A. Oil penetrates the core more easily B. Eddy current loss is reduced C. Less lamination is required for the windings D. Turn ratio is higher than voltage ratio

Description : 19 Transformer cores are built up from laminations rather than from solid metal so that A. Oil penetrates the core more easily B. Eddy current loss is reduced C. Less lamination is required for the windings D. Turn ratio is higher than voltage ratio

Last Answer : B. Eddy current loss is reduced

I13) In an ideal transformer A. windings have no resistance B. core has no losses C. core has infinite permeability D. all of the above

Description : 13) In an ideal transformer A. windings have no resistance B. core has no losses C. core has infinite permeability D. all of the above

Last Answer : D. All of the above

10] The main reason for generation of harmonics in a transformer could be A. Fluctuating load B. Poor insulation C. Mechanical vibrations D. Saturation of core

Description : 10] The main reason for generation of harmonics in a transformer could be A. Fluctuating load B. Poor insulation C. Mechanical vibrations D. Saturation of core

Last Answer : D) saturation of core

Which of the following properties is not necessarily desirable in the material for transformer core? A. Mechanical strength B. Low hysteresis loss C. High thermal conductivity D. High permeability

Description : Which of the following properties is not necessarily desirable in the material for transformer core? A. Mechanical strength B. Low hysteresis loss C. High thermal conductivity D. High permeability

Last Answer : C) high thermal conductivity

Material used for construction of transformer core is usually A. 0.4mm to 0.5 mm B. 4mm to 5 mm C. 14mm to 15 mm D. 25mm to 40 mm

Description : Material used for construction of transformer core is usually A. 0.4mm to 0.5 mm B. 4mm to 5 mm C. 14mm to 15 mm D. 25mm to 40 mm

Last Answer : d) 25mm to 40mm

State any four characteristics of core type transformer.

Description : State any four characteristics of core type transformer.

Last Answer : Characteristics of core type transformer: i) It has one window. ii) It has one magnetic circuit. iii) Core surrounds the winding. iv) Average length of core is more. v) Area of cross ... Better cooling for winding. vii) Mechnical strength is comparatively less. viii) Repair and maintenance is easy.

A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The

Description : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is

Last Answer : A 40 kVA transformer has a core loss of 400 W and a full load copper loss of 800 W. The proportion of full load at maximum efficiency is 0.707

The core construction is like spokes of a wheel in following transformer:

Description : The core construction is like spokes of a wheel in following transformer:  (A) Berry Type Transformer (B) Core Type Transformer (C) Shell Type Transformer (D) None of the above

Last Answer : The core construction is like spokes of a wheel in following transformer:  Berry Type Transformer

The desirable properties of transformer core material are

Description : The desirable properties of transformer core material are  (1) low permeability and low hysteresis loss. (2) high permeability and high hysteresis loss. (3) high permeability and low hysteresis loss. (4) low permeability and hysteresis loss.

Last Answer : The desirable properties of transformer core material are high permeability and low hysteresis loss.

The main purpose of using core in a transformer is to

Description : The main purpose of using core in a transformer is to (A) decrease iron losses (B) eliminate magnetic hysteresis (C) reduce reluctance of the common magnetic circuit (D) prevent eddy current loss

Last Answer : Reduce Relucatnce of the common magnetic circuit.

The purpose of providing an iron core in a transformer is to?

Last Answer : The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.

The purpose of providing iron core in a step-up transformer is?

Last Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.

Material used for construction of transformer core is usually?

Last Answer : Material used for construction of transformer core is usually silicon steel.

The core used in high frequency transformer is usually?

Last Answer : The core used in high frequency transformer is usually air core .

When secondary of a current transformer is open-circuited its iron core will be?

Description : When secondary of a current transformer is open-circuited its iron core will be?

Last Answer : When secondary of a current transformer is open-circuited its iron core will be hot because of heavy iron losses taking place in it due to high flux density.