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what is transformer ?

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Transformer is a device which is used to convert AC electricity from one voltage to another voltage without any change in frequency .
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Description : What is the back E.M.F in Transformer ?

Answer : Back emf in transformer is when apply voltage in primary side of transformer. This voltage produce flux according to Faraday law electro magnetic induction. This flux called mutual flux and this ... secondary flux oppos the applied voltage according to lenz law. its called back emf of transformer

Description : What is an isolation transformer? State any two applications of isolation transformer.

Answer : i) Isolation transformers are specially designed transformers for providing electrical isolation between primary & secondary windings. The transformer has primary and secondary windings placed on the common core ... ground: ii) Reduction of voltage spikes iii) It acts as a decoupling device.

Description : State what is the significance of conducting phasing out test on a 3-phase transformer? Explain its procedure with a suitable connection diagram.

Answer : -Short primary & secondary winding of other phases expect the one under test. -Connect voltmeter to secondary winding. -A small DC current is circulated through the primary winding through ... . -The test repeated for finding out remaining concerned secondary windings in the same manner.

Description : What will be the efficiency when the transformer operates at unity power factor and 60% of full load 

Answer : What will be the efficiency when the transformer operates at unity power factor and 60% of full load 96.5%

Description : What should be kVA rating of each transformer in V-V bank when three phase balanced load is 40 kVA ? (A) 19 (B) 28 (C) 37 (D) 23

Answer : What should be kVA rating of each transformer in V-V bank when three phase balanced load is 40 kVA ? (A) 19 (B) 28 (C) 37 (D) 23

Description : What will happen if the primary of a transformer is connected to D.C. supply?  (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn 

Answer : What will happen if the primary of a transformer is connected to D.C. supply?  (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn 

Description : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:  (A) Eddy Current and Hysteresis losses will be ... Current will be too much high  (C) Transformer may start to smoke and burn  (D) No effect

Answer : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:  (A) Eddy Current and Hysteresis losses will be ... will be too much high  (C) Transformer may start to smoke and burn  (D) No effect

Description : What is a capacitor voltage transformer? A) It is a transformer used in power systems to step up low voltage signals and provide extra high voltage B) It is a transformer used in power systems ... in power systems to step down extra high voltage signals and provide low voltage D) None of these

Answer : What is a capacitor voltage transformer? A) It is a transformer used in power systems to step up low voltage signals and provide extra high voltage B) It is a transformer used in power systems ... power systems to step down extra high voltage signals and provide low voltage D) None of these

Description : What is the moving part of a linear variable differential transformer?  a) Primary c) Secondary b) Diaphragm d) Core

Answer : What is the moving part of a linear variable differential transformer?  Core

Description : What is the basic principle of operation of a transformer?  (A) Self-induction (B) Mutual-induction (C) Static-induction (D) Dynamic-induction 

Answer : B.  Transformer works on principle of MUTUAL INDUCTION. When voltage is applied to the primary winding of the transformer, current flows through the current called magnetising current results in ... . Thus power flow from primary to secondary circuit is simply based on the mutual induction.

Answer : Much higher efficiency of transformer compared with that of electrical motors of the same power.

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

Answer : In short circuit test of transformer the low voltage side is short circuited . On high voltage side the voltmeter is connected in parallel and ammeter in series and also a wattmeter is ... circuit test is done for determining impedance and losses. In this test iron losses is neglected.

Description : what are the uses of current transformer ?

Answer : Uses of current transformer are as follows :A current transformer is use to measure Alternating current.A current transformer is used in meters.A current transformer is used in ammeters. ... .Current transformer is use with circuit breaker.Current transformer is use for overcurrent fault protection.

Description : what are the types of transformer ?

Answer : Power transformer, instrument transformer, pulse transformer, RF transformer, IF transformer, audio transformer, distribution transformer etc. are the types of transformer.

Description : Select insulating materials for following parts : (i) Insulation between heating element and base plate of electric iron. (ii) Insulation used over copper or aluminium conductor used for making coils. (iii) Transformer bushings. (iv) Insulation between transmission line and pole.

Answer : Parts Insulating Materials  Insulation between heating element and base plate of electric iron. Mica Insulation used over copper or aluminium conductor used for making coils.  ... Transformer bushings Porcelain  Insulation between transmission line and pole. Porcelain

Description : Explain the procedure to perform Short Circuit test on single phase transformer with circuit diagram.

Answer : It is stepping up or down the voltage, to step up voltage, it has few coils in primary core than secondary, to step down voltage it has more coils in secondary than primary 

Description : allenergy conservation techniques of electrical motor and transformer 

Description : function of equipment’s used in sub-stations : (i) Earth Switch (ii) Relay (iii) Lighting Arrester (iv) Auxiliary transformer 

Answer : (i) Earth Switch   It's function is to discharge the ground capacitance when line is open circuited for maintenance purpose by isolator.) Earthing switch is inter - locked with isolator from the safety point ... 3-ph, 4wire, 400V) to give supply to control room, area lighting, staff quarters etc, 

Description : (a) Define permeability. (b) Define MMF. (c) Define form factor of an alternating quantity. (d) Define frequency and time period of an alternating quality. (e) Define transformation ratio of transformer. ... and state the meaning of each term used. (g) Give two applications of single phase motors. 

Answer : Permeability : It is the ability of a magnetic/Non magnetic material to allow setting up of flux in it.  MMF : The magneto motive force (MMF) is the force required to setup flux in a magnetic / ... applications of single phase motors : Water pumps, ceiling fan, lathe machine

Description :  transformer coupled amplifier

Answer :  transformer coupled amplifier

Answer : Power = voltage X Current As per the windings in the primary side and secondary side the voltage and current will change accordingly.

Description : Transformer efficiency

Answer : Transformer efficiency

Description : Why circuit breaker connect b)w two transformer  (same rating

Answer : Because two transformers connection is in parallel to share the load if any transformer is receives the surge current because of the fault so to protect the other transformer from the fault. 

Answer : According to our application, we need low voltage and high voltage transformer.  High voltage tsansformer also called step up transformer. Low voltage transformer also called step down transformer ... tranformer used in consumer side or substation or special application like battery,etc...

Answer : Turns ratio= N1/ N2 IN Scott connection Main transformer turns ratio = N1 /N2 Teaser transformer turns ratio= 0.866N1/N2 Where N1= number of turns in primary winding N2= number of turns in secondary winding

Answer : Transformer core is laminated to reduce eddy current. Eddy current cause energy to lose from transformer 

Description : Explain the different types of transformer cooling.

Answer : Types of cooling systems in a transformer : Transformer cooling may be classified as natural and forced. Oil natural, air natural Oil natural, air forced Oil forced, air natural Oil forced, air forced OIl forced, water forced

Description : Explain the criteria of selection of power transformer.

Answer : Selection Criteria for Power Transformer:  1) Ratings - The kVA ratings should comply with IS:10028 (Part l)-1985. The noload secondary voltage should be 5 % more than nominal voltage to ... ) Cooling - The transformers covered in this group are generally ONAN, ONAN/ONAF, ONAN/ONAF/OFAF.

Description : List the conditions for parallel operation of three phase transformer.

Answer : Conditions for Parallel operation of 3 phase transformer: 1) Voltage ratings of both the transformers must be identical. 2) Percentage / p.u. impedances should be equal in magnitude. 3) X/R ratio of ... between primary & secondary voltages must be same. 6) Phase sequence of both must be same.

Description : Give the criteria for selection of distribution transformer as per IS:10028 (part-I) 1985.

Answer : Criteria for selection of distribution transformer as per IS:10028 (part-I) 1985: 1) Total connected load. 2) Load Diversity factor. 3) Expected daily load curve. 4) Type of loads: ( ... or trends or forecasting. 10) Ambient conditions for deciding insulation class. 11) Tap changing requirement.

Description : Give the specification of three phase transformer as per IS 1180(Part-1) 1989. 

Answer : Specification of 3-phase transformer: 1) kVA rating of transformer 2) Voltage ratings for the primary and secondary voltages 3) HV and LV currents 4) Operating frequency of the transformer 5) % impedance of ... the manufacturer 16) Weight of core 17) Weight of winding 18) Volume of oil in litres.

Description : Draw schematic diagram of welding transformer showing constructional features of a welding transformer. Also explain its working.

Answer : Constructional features of welding transformer: Working of welding transformer: i) It is a step down transformer that reduces the voltage from the source voltage to a voltage desired according to the demands of ... 230 V, 415 V Secondary voltage - 40 to 60 V Secondary current - 200 to 600 A

Description : With the help of neat diagram, explain the construction of current transformer. 

Answer : Construction of current transformer:   C.T. has bar type conductor, which behaves as primary winding. The primary of C.T. carries large current Ip which is to be measured, so the bar ... sectional area is small. An ammeter of small range is connected across the secondary as shown in figure. 

Description : Compare core type and shell type transformer.

Answer : Shell Type Transformer Core Type Transformer The core surround the windings  The Winding surround the core Magnetic Flux is distributed into 2 paths  Magnetic Flux has only ... in Weight  Less in Weight  It has two windows opening  It has one window opening

Description : Give the classification of transformer based on: i) Construction ii) Voltage level iii) Number of phases iv) Applications

Answer : Classification of transformer based on: i) Construction: Shell type, Core type, Berry type ii) Voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) Applications: Power T/F, Distribution T/F

Answer : Advantages of three phase transformer over bank of single phase transformers:  For identical magnitudes of power transformation, i) Saving in copper conductor. ii) Saving in electromagnetic core material. ... material such as insulating oil. v) Saving in overall cost. vi) Higher efficiency.

Description : State four properties of Ideal transformer:

Answer : Properties of Ideal transformer: 1) No losses (iron and copper), hence no temperature rise 2) Zero winding resistance and leakage reactance 3) No voltage drop i.e. E1 = V1, ... R losses]   4) Zero magnetic leakage (coefficient of coupling between primary and secondary windings is unity).

Description : for Delta-Star connection of 3-phase transformer: i) Draw the connection diagram ii) List any two advantages of this connection iii) State its area of application. 

Answer : Disadvantages: i) In this type of connection, the secondary voltage is not in phase with the primary. Hence it is not possible to operate this connection in parallel with star-star or delta-delta ... iv) As line current is equal to phase current the conductor size of winding should be large. 

Description : Describe any two functions of Isolation transformer.

Answer : Function of isolation transformer:  1. Primary purpose of isolation transformer is to isolate the two circuits and not to step-up or step-down the voltage. 2. The ground connection ... secondary. 5. The isolation transformer reduces the transients of high amplitudes and short time interval 

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