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
Description : Reduction in core losses and increase in permeability are obtained with transformer employing?
Last Answer : Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.
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
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
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
Description : 59.An ideal transformer has infinite values of primary and secondary inductances. The statement is A. True B. False
Last Answer : B. False
Last Answer : An ideal transformer has infinite values of primary and secondary inductances. The statement is false.
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
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
Description : 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
Last Answer : D. To take care of the expansion and contraction of transformer oil due to variation of temperature of surroundings
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
Description : 57 In a transformer the resistance between its primary and secondary is A. Zero B. 1Ω C. 1000 Ω D. Infinite
Last Answer : D. Infinite
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
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
Description : What are the transformer losses?
Last Answer : Answer: TRANSFORMER LOSSES - There are mainly two kinds of losses in a transformer namely 1. Copper loss (ohmic loss) and 2.magnetic loss (core loss). Copper losses are caused by the ... ohmic loss the following two losses are also present in the transformer stray load loss and dielectric loss.
Description : Explain about the losses in Transformer?
Last Answer : TRANSFORMER LOSSES - Transformer losses have two sourcescopper loss and magnetic loss. Copper losses are caused by the resistance of the wire (I2R). Magnetic losses are caused by eddy currents ... current. Eddy-current loss, however, is different for each frequency passed through the transformer.
Description : Why are iron losses considered as constant losses in transformer?
Last Answer : Iron losses depend on supply frequency and flux density in the core. For all normal operations, the frequency of flux reversals which is same as supply frequency is constant and the value of flux density ... . Hence iron losses remain constant under all load conditions. i-e from no-load to full-load
Description : 64)During the short-circuit test on a small transformer the frequency is increased from 50-200Hz. The copper losses will increase by a factor of A. 16 B. 4 C. 1 D. 1/4
Last Answer : A) 16
Description : 48.During light loads, the transformer efficiency is low because A. Secondary output is low B. Transformer losses are high C. Fixed loss is high in proportion to the output D. Cu loss is small
Last Answer : C. Fixed loss is high in proportion to the output
Description : 42 The efficiency of a transformer will be maximum when A. copper losses = hysteresis losses B. Hysteresis losses = eddy current losses C. Eddy current losses = copper losses D. Copper losses = iron losses
Last Answer : D. Copper losses = iron losses
Description : During short circuit test iron losses are negligible because A. The current on secondary side is negligible B. The voltage on secondary side does not vary C. The voltage applied on primary side is low D. Full-load current is not supplied to the transformer
Last Answer : C) the voltage applied on primary side is low
Description : 7 The main advantage of auto transformer over a two winding transformer is A. Hysteresis losses are reduced B. Saving in winding material C. Copper losses are negligible D. Eddy losses are totally eliminated
Last Answer : A) hysteresis losses is reduced
Description : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?
Last Answer : In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses.
Description : 71 High frequency transformers sometimes make use of ferrite cores because it has A. High specific gravity B. High resistance C. High hysteresis D. low permeability
Last Answer : B. High resistance
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.
Description : What is the purpose of laminating the core in a transformer?
Last Answer : In order to minimize eddy current loss.
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
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.
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
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
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
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
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.
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
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
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.
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.
Last Answer : The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.
Last Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.
Last Answer : Material used for construction of transformer core is usually silicon steel.
Last Answer : The core used in high frequency transformer is usually air core .
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.
Description : The size of a transformer core will depend on?
Last Answer : The size of a transformer core will depend on frequency and area of the core.
Description : Why does the core of a transformer need to be laminated?
Last Answer : Transformer cores are laminated to reduce eddy current loss.
Last Answer : Transformer core is laminated to reduce Eddy current losses.
Description : What is an ideal transformer?
Last Answer : A. Transformer having an overall efficiency of 100 per cent is called an ideal transformer.
Description : What are the properties of ideal transformer?
Last Answer : 1.There should be no losses 2.The winding should have zero resistance 3.The leakage flux should be zero 4. The permeability of core should be so high that the negligible current is required to establish the flux in it.
Last Answer : An ideal transformer is one which has no losses and magnetic leakage.
Last Answer : An ideal transformer will have maximum efficiency at a load such that copper loss equal to iron loss.