Description : 1 Sumpner's test is conducted on transformers to find A. Temperature B. Stray losses C. All-day efficiency D. None of the above
Last Answer : A. Temperature
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 : The efficiency of a transformer is mainly dependent on: (A) core losses(B) copper losses stray losses (D) dielectric losses
Last Answer : The efficiency of a transformer is mainly dependent on: core losses
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 : A transformer has maximum efficiency at 3/4 full load. The ratio of its iron losses and full load copper loss is : - a) 16/9 b) 4 / 3 c) 3/4 d) 9 /16
Last Answer : A transformer has maximum efficiency at 3/4 full load. The ratio of its iron losses and full load copper loss is : - 9 /16
Description : Which of the following losses is/are present in every direct current generator armature? A. Winding copper loss B. Core eddy current loss C. Magnetic hysteresis loss D. All of the above.
Last Answer : Answer: D
Description : An open coil in a transformer will be indicated by which of the listed conditions? A. 'zero' resistance accompanied by high inductance B. no resistance accompanied by stray inductance C. infinite resistance in addition to no inductance D. infinite resistance in addition to normal inductance
Last Answer : Answer: C
Description : The harmonic currents in a power transformer does not cause increase in: a) Secondary voltage b) Core loss c) Copper loss d) Magnetic interference with protective relays
Last Answer : Ans: A
Description : What is the percentage of stray losses in DC machine?
Last Answer : Percentage of stray losses in DC machine is about 1 % .
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 : 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 : 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
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 : Which of the following tests is not done for transformer oil? (A) Flash point and acid value (B) Aniline point (C) Dielectric strength (D) Copper strip corrosion test
Last Answer : (B) Aniline poin
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 : A saturable-core reactor operates on the principle of controlling a load winding's inductance by varying the core's _____________. A. dielectric B. permeability C. reactance D. inductance
Last Answer : Answer: B
Description : ECE Board Exam March 1996 That dielectric material of an optical fiber surrounding the core A. Cladding B. Armor C. Shield D. Cover
Last Answer : A. Cladding
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 : 70] Silicon steel used in laminations mainly reduces A. Hysteresis loss B. Eddy current losses C. Copper loss D. All of the above
Last Answer : A. Hysteresis loss
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 : 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 : A 500 kVA, 3-phase transformer has iron losses of 300 W and full load copper losses of 600 W. The percentage load at which the transformer is expected to have maximum efficiency is (A) 50.0% (B) 70.7% (C) 141.4% (D) 200.0%
Last Answer : A 500 kVA, 3-phase transformer has iron losses of 300 W and full load copper losses of 600 W. The percentage load at which the transformer is expected to have maximum efficiency is 70.7%
Description : Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is?
Last Answer : Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is approximately equal to 1.
Description : Although saturable reactors are extremely useful in some applications, their gain is low because of ____________. A. core hysteresis losses B. inductive reactance in the control winding C. IR drop throughout the load winding D. all of the above
Last Answer : Answer: A
Description : Which of the following statements about copper wire sized by the AWG rating is correct? A. Number 12 AWG wire has a higher current rating than number 10 AWG wire. B. Number 10 AWG wire has a higher ... Number 12 AWG wire at 25°C has more resistance per 1000 feet than No. 10 AWG wire at 25°C.
Description : Which of the following statements concerning copper wire sized by AWG numbers is correct? A. Number 12 AWG wire has a higher current rating than 10 AWG wire. B. Number 12 AWG wire at 25°C has more ... dielectric strength than 12 AWG wire. D. Number 12 AWG wire is larger than number 10 AWG wire.
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 : What are the losses in a power transformer and mention how these losses can be minimised?
Last Answer : There are two losses in a transformer. a. Iron losses. b. Copper losses. Iron losses - Iron losses constitutes of two losses. a. Eddy current losses, these are due to the induced emf in the core ... the load current I - current through winding. r - resistance of winding. t - time duration.
Description : What are the losses in transformer?
Last Answer : In transformer there are losses due to, 1. Resistance of the winding (copper losses). 2. Eddy current and Hysterisis in the iron parts and core (core and iron losses) 3. Losses due to leakage reactance ... cosiderable manner. Copper losses are variable and can be calculated by Ip 2 *rp and Is 2 *rs.
Description : Explain different losses in a transformer.
Last Answer : There are two types of losses occurring in transformer: Constant losses or Iron losses: The losses that occur in the core are known as core losses or iron losses. Two types of iron ... upon the loading conditions of the transformers. Therefore, these losses are also called as variable losses.
Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.
Last Answer : (A) Both eddy current and hysteresis losses decreases.
Description : The armature of a dc machine is laminated to reduce: (A) Eddy current loss (B) Hysteresis loss (C) copper losses (D) friction and windage losses
Last Answer : Ans: A Thinner the laminations, greater is the resistance offered to the induced e.m.f., smaller the current and hence lesser the I2R loss in the core.
Description : Due to which of the following reasons the cables should not be operated too hot ? (a) The oil may loose its viscosity and it may start drawing off from higher levels (b) Expansion of the ... instability may rise due to the rapid increase of dielectric losses with temperature (e) All of the above
Last Answer : (e) All of the above
Description : What is the term used to refer to the losses which can be traced to the dielectric of a capacitor?
Last Answer : Power losses.
Description : What types of losses cause the dielectric material between the conductors to be heated?
Last Answer : Dielectric losses.
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 : 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 : 40 No load test on a transformer is carried out to find A. Copper loss B. magnetising current C. Magnetising current and loss D. Efficiency of the transformer
Last Answer : C. Magnetising current and loss
Description : 22 No load test on a transformer is carried out to find A. copper loss B. magnetising current C. Magnetising current and no load loss D. Efficiency of the transformer
Last Answer : C. Magnetising current and no load loss
Description : When a solid-state component of an electronic circuit is mounted to a metallic mass, the general purpose of that mass is to ____________. A. prevent vibration damage to delicate components B. prevent ... damage to solid-state components C. dissipate stray magnetic currents D. act as a heat sink
Description : The purpose of an impressed current cathodic protection system aboard ship is to _______________. A. prevent corrosion of the hull, propeller, rudder and line shafting B. neutralize the vessel's ... the presence of salt air D. maintain a minimum constant alternator load to prevent overheating
Description : Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer
Description : In replacing a defective transformer with a new one, which of the following actions must be carried out to insure proper operation of the equipment it serves? A. The secondary leads must be grounded ... magnetize it. D. The iron core must be grounded for 10 minutes to remove any residual magnetism.
Description : The hook-on AC volt-ammeter consists essentially of a split-core and a rectifiertype instrument connected to the secondary winding of a _____________. A. potential transformer B. control transformer C. current transformer D. reactance transformer
Description : When a transformer is used to step down voltage, the low voltage winding is _____________. A. part of the core B. the primary coil C. not insulated D. the secondary coil
Description : If a transformer is connected to a DC source, the transformer will overload at the ____________. A. contacts B. primary coil C. secondary coil D. core