Description : A ferrite core has less eddy current loss than an iron core because ferrites have (A) High resistance. (B) Low resistance. (C) Low permeability. (D) High hysteresis.
Last Answer : (A) High resistance.
Description : Straight silicon steel (containing Si from 0.5 to 5%) because of their low hysteresis loss and high magnetic permeability are used for electrical appliances. Which of the following electrical ... /generators (B) Generators and small motors (C) Induction motors (D) High frequency transformers
Last Answer : (D) High frequency transformers
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 : 24 Transformer cores are laminated in order to A. simplify its construction B. minimise eddy current loss C. reduce cost D. reduce hysteresis loss
Last Answer : B. Minimise eddy current loss
Description : 4 Helical coils can be used on A. Low voltage side of high kVA transformers B. High frequency transformers C. High voltage side of small capacity transformers D. High voltage side of high kVA rating transformers
Last Answer : A) low voltage side of high KVA transformer
Description : 47 Cross over windings are used in A. Low voltage side of high kVA rating transformers B. Current transformers C. High voltage side of high kVA rating transformers D. High voltage side of low kVA rating transformers
Last Answer : D. High voltage side of low kVA rating transformers
Description : Can the transformers be used at higher frequencies than rated frequency?
Last Answer : A. Yes. Transformers can be used at higher frequencies than rated frequency. However as the frequency increases voltage regulation decreases.
Description : Why stepped cores are used?
Last Answer : (i) To reduce the space effectively. (ii) To obtain reduced length of mean turn of the windings. (iii) To reduce I² R loss.
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 : 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
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.
Description : Magnetising steel is normals difficult because (a) it corrodes easily (6) it has high permeability (c) it has high specific gravity (d) it has low permeability
Last Answer : (d) it has low permeability
Description : Mention the factors on which hysteresis loss depends?
Last Answer : (i) Quality and amount of iron in the core (ii) Flux density and (iii) Frequency.
Description : How to minimize Hysteresis loss?
Last Answer : By using good magnetic material. By using less value of Magnetic flux density
Description : What is hysteresis loss in transformer?
Last Answer : The magneto motive force or mmf applied in the transformer core is alternating. For every cycle due to this domain reversal, there will be extra work done. For this reason, there will be a consumption of electrical energy which is known as Hysteresis loss of transformer.
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 : 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
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 : 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 : 9 Which loss is not common between a transformer and rotating machines? A. Eddy current loss B. Copper loss C. Windage loss D. Hysteresis loss
Last Answer : A. Eddy current loss
Description : 17. Which type of loss is not common to transformer and rotating machines? A. Eddy current loss B. Copper loss C. Hysteresis loss D. Windage loss
Last Answer : D. Windage loss
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 transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are (A) 140 W (B) 180 W (C) 240 W (D) 480 W
Last Answer : A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are 240 W
Description : Materials that retain a large part of their magnetization, after the magnetizing force is removed, are said to have _____________. A. low hysteresis loss B. high flux density C. high permanence D. high permeability
Last Answer : Answer: C
Description : Materials subjected to rapid reversal of magnetism should have (a) large area oiB-H loop (b) high permeability and low hysteresis loss (c) high co-ercivity and high retentivity (d) high co-ercivity and low density
Last Answer : (b) high permeability and low hysteresis loss
Description : The armature cores of the D.C. motors are constructed with laminations to ___________. A. eliminate hysteresis B. minimize brush sparking C. reduce eddy current losses D. compensate for armature reaction
Description : Armature cores in a DC generator are made of laminated steel sheets to _____________. A. fit the curvature of the frame B. increase the hysteresis effect C. reduce eddy current losses D. allow for easy assembly
Description : Why we need isolation transformers in power circuit ? why cant we use breakers to isolate?
Last Answer : In Isolation transformer is used, if there is change in parameter values of any side, the other side parameters will remain unchanged.
Description : Why Silica gel is used in transformers?
Last Answer : Silica Gel is used to remove the moisture in the air entering in to the transformer. During the breathing of the transformer air enters in to the transformer. This air makes contact with the hot ... Silica gel crystals will be in blue color initially and after absorbing moisture it turns to pink.
Description : What are the conditions for parallel operation of two transformers ?
Last Answer : Transformers which are to be operated parallel should have to satisfy the following conditions: Polarities of both the transformers should be same else lead to short circuit Voltage rating of ... Phase displacement of transformers should be same Phase sequence of two transformers should be same
Description : What is the significance of vector grouping in Power Transformers?
Last Answer : Answer:Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phace difference betweent ... Delta primary, Wye Secondry and the current is at 11 o clock reffered to the voltage.
Description : How is magnetic leakage reduced to a minimum in commercial transformers?
Last Answer : By interleaving the primary and secondary windings.
Description : Can Transformers be Reconnected as Autotransformers to Increase Their KVA Rating?
Last Answer : ANSWER: Several of standard single phase transformers can be connected as autotransformers. The KVA capacity will be greatly increased when used as an Autotransformer, in comparison to the ... This voltage is normally used for operating fluorescent lamps or similar devices requiring 277 volts
Description : What is BIL and How Does it Apply to our Transformers ?
Last Answer : ANSWER: BIL is an abbreviation for Basic Impulse Level. Impulse tests are dielectric tests that consist of the applica¬tion of a high frequency steep wave front voltage between windings ... breakdowns when his system is properly protected with lightning arrestors or similar surge protection devices.
Description : What is Meant by "Impedance" in Transformers?
Last Answer : ANSWER: Impedance is the current limiting characteristic of a transformer and is expressed in percentage.
Description : Can 60 Hz Transformers be Used at Higher Frequencies?
Last Answer : A: Transformers can be used at fre¬quencies above 50 Hz up through 400 Hz with no limitations provided nameplate voltages are not exceeded. However, 50 Hz transformers will have less voltage ... Where better regulation and smaller physical size are required, contact us for special 400 Hz designs.
Description : What are the Conditions for parallel operation of transformers?
Last Answer : A. a) Same voltage ratio of transformer: If two transformers of different voltage ratio, are connected in parallel with same primary supply voltage, there will be a difference in secondary voltages. If ... not in same phase sequence, during the cycle, each pair of phases will be short circuited.
Description : What are the advantages of parallel operation of transformers?
Last Answer : A. 1) To maximize electrical power system efficiency: Generally electrical power transformer gives the maximum efficiency at full load. If we run numbers of transformers in parallel, we can switch ... running in parallel can be removed from system to balance the capital investment and its return.
Description : What is meant by “impedance” in transformers? Why is it important?
Last Answer : A. Impedance is the current limiting characteristic of a transformer and is expressed in percentage. It is used for determining the interrupting capacity of a circuit breaker or fuse employed to protect the primary of a transformer
Description : Can Single Phase Transformers be used for Three Phase applications?
Last Answer : A. Yes. Three phase transformers are sometimes not readily available whereas single phase transformers can generally be found in stock. Three single phase transformers can be used in delta connected primary and ... K VA single phase transformers can be used to accommodate a 30 KVA three phase load.
Description : Can Transformers develop Three Phase power from a Single Phase source?
Last Answer : A. NO. Phase converters or phase shifting devices such as reactors and capacitors are required to convert single phase power to three phase.
Last Answer : A. Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phase difference between the ... Delta primary, Wye Secondary and the current is at 11 o clock referred to the voltage.
Description : What are the types of cooling systems it transformers?
Last Answer : A. 1. ONAN (oil natural, air natural) 2. ONAF (oil natural, air forced) 3. OFAF (oil forced, air forced) 4. ODWF (oil direct, water forced) 5. OFAN (oil forced, air forced)
Description : Why Delta Star Transformers are used for Lighting Loads?
Last Answer : A. For lighting loads, neutral conductor is must and hence the secondary must be star winding.This lighting load is always unbalanced in all three phases. To minimize the current unbalance in the primary we use delta winding in the primary. So delta / star transformer is used for lighting loads.
Description : How do you classify transformers based on construction?
Last Answer : A. Based on construction transformers are of two types. They are distinguished from each other based on merely the manner by which primary and secondary windings are placed around the core. ... surrounds considerable part of windings. Another recent development is wound core type or spiral core.
Description : Why do transformers hum?
Last Answer : Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when magnetized. When the magnetization is taken away, it goes back to its original condition ... core. The degree of flux determines the amount of magnetostriction and hence, the noise level.
Description : Is it Possible to Change Three Phase to Two Phase or Vice-Versa with Standard Transformers?
Last Answer : Yes. This is a very practical application for standard single phase off-the-shelf transformers. Some typical voltage combinations are as follows: 480 volts three phase to 240 volts two phase, or 240 volts ... 240 volts three phase to 240 volts two phase. Please refer to us for an exact schematic.
Description : Can 60 Hz transformers be operated at 50 Hz?
Last Answer : The transformers rated below 1 KVA can be used on 50 Hz service. Transformers 1 KVA and larger, rated at 60 Hz, should not be used on 50 Hz service, due to the higher losses and resultant heat ... designs are required for this service. However, any 50 Hz transformer will operate on a 60 Hz service.