The secondary of a current transformer is always short-circuited under operating conditions because it?
Last Answer : The secondary of a current transformer is always short-circuited under operating conditions because it avoids core saturation and high voltage induction.
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107 views
1 answer
asked
Mar 19, 2018
by
anonymous

A ferrite core has less eddy current loss than an iron core because?
Last Answer : A ferrite core has less eddy current loss than an iron core because ferrites have high hysteresis.
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382 views
1 answer
asked
Mar 25, 2018
by
anonymous

In a transformer the resistance between its primary and secondary should be?
Last Answer : In a transformer the resistance between its primary and secondary should be infinity.
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254 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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132 views
1 answer
asked
Jul 27, 2019
by
anonymous

Last Answer : Material used for construction of transformer core is usually silicon steel.
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241 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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114 views
1 answer
asked
Mar 19, 2018
by
anonymous

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.
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615 views
1 answer
asked
Mar 19, 2018
by
anonymous

In an actual transformer the iron loss remains practically constant from no load to full load because?
Last Answer : In an actual transformer the iron loss remains practically constant from no load to full load because core flux remains practically constant.
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113 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : If the supply frequency to the transformer is increased, the iron loss will increase.
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170 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Iron loss of a transformer can be measured by low power factor wattmeter.
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104 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : When a conductor carries more current on the surface as compared to core, it is due to skin effect.
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171 views
1 answer
asked
Mar 20, 2018
by
anonymous

Increasing the number of turns of wire on the secondary of a transformer will (A) Decrease the secondary current (B) Increase the primary current (C) Have no effect on the secondary current (D) Increase the secondary current
Last Answer : Increasing the number of turns of wire on the secondary of a transformer will Decrease the secondary current
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1.3k views
1 answer
asked
May 8, 2018
by
anonymous

A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary? (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts
Last Answer : A certain transformer has 200 turns in the primary winding, 50 turns in the secondary winding and 120 volts applied to the primary. What is the voltage across the secondary? (A) 30 Volts (B) 480 Volts (C) 120 Volts (D) 60 Volts
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223 views
1 answer
asked
May 8, 2018
by
anonymous

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
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774 views
1 answer
asked
May 8, 2018
by
anonymous

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
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133 views
1 answer
asked
May 8, 2018
by
anonymous

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.
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230 views
1 answer
asked
May 1, 2018
by
anonymous

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.
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2.0k views
2 answers
asked
Apr 28, 2018
by
anonymous

Why does the core of a transformer need to be laminated?
Last Answer : Transformer cores are laminated to reduce eddy current loss.
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122 views
1 answer
asked
Mar 14, 2018
by
anonymous

Last Answer : Transformer core is laminated to reduce Eddy current losses.
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112 views
1 answer
asked
Sep 30, 2017
by
anonymous

Eddy current damping cannot be used for moving iron instrument because
Last Answer : Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument
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2.3k views
1 answer
asked
Apr 26, 2018
by
anonymous

At full -load of a transformer, the iron loss and copper loss are 3000 W and 4000 W respectively. Then total loss at maximum efficiency is : (A) 7000 W (B) 6000 W (C) 8000 W (D) 4000 W
Last Answer : At full -load of a transformer, the iron loss and copper loss are 3000 W and 4000 W respectively. Then total loss at maximum efficiency is : 6000 W
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303 views
1 answer
asked
Apr 30, 2018
by
anonymous

Even at no-load, a transformer draws current from the mains. Why?
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114 views
0 answers
asked
Apr 28, 2020
by
anonymous

For a transformer, operating at constant load current, maximum efficiency will occur at?
Last Answer : For a transformer, operating at constant load current, maximum efficiency will occur at unity power factor.
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124 views
1 answer
asked
Mar 19, 2018
by
anonymous

In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of?
Last Answer : In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of less than 15A.
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156 views
1 answer
asked
Mar 19, 2018
by
anonymous

If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then (A) zero sequence currents are present on both sides of the transformer (B) ... side (D) zero sequence currents are present on the primary side but not on the secondary side
Last Answer : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer
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228 views
1 answer
asked
Apr 29, 2018
by
anonymous

The operating point of a protective current transformer is near the
Last Answer : The operating point of a protective current transformer is near the Ankle point
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126 views
1 answer
asked
May 8, 2018
by
anonymous

Step-down transformer converts high voltage and low current into: (A) How voltage and high current (B) High voltage and low current (C) Low voltage and high current (D) None of the above
Last Answer : Step-down transformer converts high voltage and low current into: Low voltage and high current
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125 views
1 answer
asked
May 8, 2018
by
anonymous

The inrush current of a transformer at no load is maximum if the supply voltage is switched on (1) at peak voltage value (2) at zero voltage value (3) at half voltage value (4) at 0.866 time voltage value
Last Answer : At 0.866 time voltage value
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114 views
2 answers
asked
Apr 30, 2018
by
anonymous
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In a single-phase transformer, the magnetizing current is (A) in phase with the no-load current (B) in quadrature with the no-load current (C) the product of no-load current and power factor (D) in phase with the flux in the core
Last Answer : In a single-phase transformer, the magnetizing current is in phase with the flux in the core
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86 views
1 answer
asked
Apr 28, 2018
by
anonymous

Last Answer : The inverse definite mean time relays are used for over current and earth fault protection of transformer against internal short-circuits.
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2.6k views
1 answer
asked
Mar 20, 2018
by
anonymous

How eddy current is produced in a transformer?
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126 views
0 answers
asked
Mar 15, 2018
by
anonymous

Last Answer : The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.
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203 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.
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546 views
1 answer
asked
Mar 19, 2018
by
anonymous

Why CT is never operated with an open secondary ?
Last Answer : CT secondary should never be kept open because it will cause saturation of the core to a high level and very high voltage will appear across the secondary which can breakdown the insulation. One terminal of PT secondary is always grounded to avoid capacitive induction and for human safety
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92 views
2 answers
asked
Sep 6, 2018
by
anonymous

66 While conducting short-circuit test on a transformer the following side is short circuited A. High voltage side B. low voltage side C. primary side D. secondary side
Last Answer : B. Low voltage side
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25 views
1 answer
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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.
Last 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
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199 views
1 answer
asked
May 7, 2020
by
anonymous

Last Answer : High Voltage side is open circuited.
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116 views
1 answer
asked
Sep 27, 2017
by
anonymous

Last Answer : The core used in high frequency transformer is usually air core .
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213 views
1 answer
asked
Mar 19, 2018
by
anonymous

Define: primary and secondary distribution system
Last Answer : i) Primary Distribution: It is a 3-phase, 3-wire transmission line connected in between receiving substation to Distribution substation. OR It is link between receiving substation & ... substation to consumer line. OR It is link between distribution transformer substation & consumer.
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167 views
1 answer
asked
May 22, 2020
by
anonymous

State the losses in secondary distribution system.
Last Answer : The losses in secondary distribution system: a) Technical losses: 1. Due to poor voltage 2. Due to unbalance load 3. Due poor quality of transformer & its components 4. Due to poor quality ... of induction type of energy meter. 3. Lack of administration. 4. Energy theft 5. Unmetered supply
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122 views
1 answer
asked
May 3, 2020
by
anonymous
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State the meaning of secondary instrument. Classify secondary instruments.
Last Answer : Secondary instruments: - Gives reading directly of the quantity being measured. - Calibrated with respect to absolute instruments Classification of Secondary instruments: 1. Depending on the ... on permissible error: i) Standard meters ii) Substandard meters iii) First grade instruments.
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76 views
1 answer
asked
Sep 6, 2018
by
anonymous

State the meaning of absolute instrument and secondary instrument.
Last Answer : Absolute instruments: These instruments read the quantity under measurement indirectly i.e. in terms of deflection, degrees and meter constant. The actual value under measurement can be calculated ... of operation (b) Depending upon permissible percentage error. (c) Depending upon application.
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113 views
2 answers
asked
Sep 6, 2018
by
anonymous

Compare primary and secondary instruments.
Last Answer : Primary instruments Secondary instruments Gives magnitude of quantity in terms of physical constants of instrument Gives reading directly of the quantity measured. Need no calibration ... . e.g. magnetic meter, induction meter, hotwire meter and electrostatic meter
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90 views
1 answer
asked
Sep 6, 2018
by
anonymous

Write difference between absolute & secondary instrument.
Last Answer : Absolute Instrument Secondary Instrument 1. These give magnitude of quantity in terms physical constants of instruments 1. These give reading directly of the quantity at the time of ... Raleigh current balance. 6. Examples - ammeter, voltmeter, amperehour meter, wattmeter etc.
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6.1k views
1 answer
asked
Sep 5, 2018
by
anonymous
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Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary
Last Answer : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary
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580 views
1 answer
asked
May 8, 2018
by
anonymous

What happens to the voltage in the secondary when the frequency of the supply in the primary is decreased? A) It increases B) It decreases C) It remains the same D) Cannot say unless the actual percentage increase in the frequency is known
Last Answer : What happens to the voltage in the secondary when the frequency of the supply in the primary is decreased? A) It increases B) It decreases C) It remains the same D) Cannot say unless the actual percentage increase in the frequency is known
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119 views
1 answer
asked
Apr 29, 2018
by
anonymous

What do you mean by secondary instruments?
Last Answer : The instruments which will give the direct readings are called secondary instruments
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95 views
1 answer
asked
Mar 10, 2018
by
anonymous

State the material used for making (1) Magnetic Core (2) Fuse element
Last Answer : The material used for making of: (1) Magnetic Core : Iron, cobalt, Nickel, CRGO, HRGO , silicon steel (2) Fuse Element: Tin- lead wire, Tinned copper wire
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209 views
1 answer
asked
May 7, 2020
by
anonymous

Core type transformers are popular in___________. (A) High voltage applications (B) Low voltage applications (C) All of the above (D) None of the above
Last Answer : Core type transformers are popular in High voltage applications
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96 views
1 answer
asked
May 8, 2018
by
anonymous

A single core lead sheathed cable with two dielectrics of permittivity 4 and 3, respectively, are subjected to same maximum stress. If the conductor diameter is 1.5 cm, the outer diameter of the first dielectric is (A) 1.125 cm (B) 1.5 cm (C ) 2 cm (D) 8 cm
Last Answer : A single core lead sheathed cable with two dielectrics of permittivity 4 and 3, respectively, are subjected to same maximum stress. If the conductor diameter is 1.5 cm, the outer diameter of the first dielectric is 2 cm
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171 views
1 answer
asked
Apr 28, 2018
by
anonymous
