What happen when Transformer is given DC supply ?
Last Answer : When DC supply is given to the transformer primary winding no back emf is induced in the transformer. Importance of Back emf is that it limits the current drawn by the machine. In the absence ... in burning down of primary winding. So when dc supply is given to transformer primary windings will burn
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10 views
1 answer
What will happen if DC supply is given on the primary of a transformer?
Last Answer : A. Mainly transformer has high inductance and low resistance. In case of DC supply there is no inductance, only resistance will act in the electrical circuit. So, high electrical current will flow through primary side of the transformer. Due to this the coil and insulation will burn out.
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4 views
1 answer
Why does a transformer only work with an AC supply?
Last Answer : The transformer work depends on the induction as main principle ,for that AC is the right means
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150 views
3 answers
asked
Mar 14, 2018
by
anonymous
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
Last 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
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538 views
1 answer
asked
May 8, 2018
by
anonymous
Write about transformer on DC.
Last Answer : Transformer on DC : Transformer cannot work on DC. Transformer works on electromagnetic induction principle. Electromagnetic induction principle means when flux linking with coil changes and EMF induced in it ... winding insulation will burn. https://youtu.be/TVp_0fIfxqY
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248 views
1 answer
asked
May 10, 2020
by
anonymous
Can transformer convert AC to DC?
Last Answer : No, Transformer cannot convert AC to DC.
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3.0k views
9 answers
asked
Dec 9, 2017
by
anonymous
What is the supply rated o/p if two single phase transformer connect to give three phase o/p from a three phase I/p?
Last Answer : A. Each transformer is only capable of supplying 86.6%of its o/p rating
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5 views
1 answer
[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
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54 views
1 answer
52 A transformer has 1000 primary turns, connected to 250V ac supply. To get 400V secondary voltage the no of secondary turns should be A. 1600 B. 250 C. 400 D. 1250
Last Answer : A. 1600
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7 views
1 answer
An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V
Last Answer : An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V
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259 views
1 answer
asked
Jun 18, 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
Last Answer : A transformer cannot raise or lower the voltage of a D.C. supply because Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero.
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344 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
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
Last Answer : Igbt alone cant convert dc to ac. igbt half bridge or full bridge or three phase topology could be used to convert dc to ac. also igbt gates should be driven by microcontroller or pwm/spwm gate driving signals ... e4(-) and g4 c2e1 and c4e3 pins are AC output pins. its name is igbt inverter.
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185 views
1 answer
asked
Feb 24, 2018
by
Amit Sharma
Explain the procedure to perform Short Circuit test on single phase transformer with circuit diagram.
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111 views
0 answers
asked
Apr 27, 2020
by
anonymous
What is the back E.M.F in Transformer ?
Last 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
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150 views
1 answer
asked
Aug 27, 2019
by
anonymous
transformer coupled amplifier
Last Answer : transformer coupled amplifier
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94 views
1 answer
asked
Aug 19, 2019
by
anonymous
72 views
0 answers
asked
Jun 29, 2019
by
anonymous
Transformer efficiency
Last Answer : Transformer efficiency
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77 views
1 answer
asked
Jun 11, 2019
by
anonymous
Give Any Three Features And Any Two Applications Of Welding Transformer.
Last Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }
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233 views
2 answers
asked
Sep 15, 2018
by
anonymous
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Explain construction and working of isolation transformer.
Last Answer : Isolation Transformer https://youtu.be/gq9kjLlhPN0
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913 views
3 answers
asked
Sep 14, 2018
by
anonymous
Write selection criteria of distribution transformer with any four points.
Last Answer : Selection Criteria for Distribution Transformer: i) Ratings - The kVA ratings should comply with IS:2026 ( Part l )-1977*. The noload secondary voltage should be 433 volts for transformers to be ... is not necessary. vi) Cooling - The transformers covered in this group are generally ONAN, AN
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230 views
2 answers
asked
Sep 14, 2018
by
anonymous
Write any four advantages of instrument transformer.
Last Answer : Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.
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183 views
1 answer
asked
Sep 6, 2018
by
anonymous
State the advantages of instrument transformer in using for extension of range of meters.
Last Answer : Advantages of instrument transformer: 1. Extension of instrument range is possible. 2. Isolation of instruments from high voltage side. 3. Power loss is less as compared to shunts and multipliers. 4 ... measurement. 5. It is economical method of range extension. 6. Increases in safety of operator.
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72 views
1 answer
asked
Sep 6, 2018
by
anonymous
Compare RC coupled, transformer coupled and direct coupled amplifier based on four points.
Last Answer : Parameter RC coupled Transformer coupled Direct coupled Coupling element Resistor and capacitor Transformer No element Impedance matching Poor Excellent good Frequency ... Low frequency amplifier,opamp Size and cost small Large and bulky least
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3.0k views
1 answer
asked
Sep 5, 2018
by
anonymous
Introduction to transformer
Last Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed ... power start transformer, autotransformer, multiphase transformer, magnetic flux linkage transformer, resonant transformer etc.
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69 views
1 answer
asked
Sep 1, 2018
by
anonymous
MATLAB design code and model description.
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76 views
0 answers
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Cylindrical type transformer has: (A) Single magnetic circuit (B) Double magnetic circuit (C) All of the above (D) None of the above
Last Answer : Cylindrical type transformer has: Single magnetic circuit
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121 views
1 answer
asked
May 8, 2018
by
anonymous
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The transformer works on the principle of: (A) Mutual induction (B) Mutual capacitance (C) All of the above (D) None of the above
Last Answer : The transformer works on the principle of: Mutual induction
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99 views
1 answer
asked
May 8, 2018
by
anonymous
The rating of transformer may be expressed in ____________. (A) kVAR (B) kW (C) kVA (D) Horse power
Last Answer : The rating of transformer may be expressed in kVA .
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614 views
1 answer
asked
May 8, 2018
by
anonymous
Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines: (A) Delta-Star (B) Star-Delta (C) Delta-Delta (D) Star-Star
Last Answer : Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines: Star-Star
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355 views
1 answer
asked
May 8, 2018
by
anonymous
Which of the following does not change in a transformer? (A) Current (B) Voltage (C) Frequency (D) All of the above
Last Answer : Which of the following does not change in a transformer? (A) Current (B) Voltage (C) Frequency (D) All of the above
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2.3k views
1 answer
asked
May 8, 2018
by
anonymous
A Step Up transformer : (A) Steps up the level of Voltage (B) Steps down the level of current (C) Step up the level of Frequency (D) (a) and (b) only
Last Answer : A Step Up transformer : (A) Steps up the level of Voltage (B) Steps down the level of current (C) Step up the level of Frequency (D) (a) and (b) only
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63 views
1 answer
asked
May 8, 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
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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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123 views
1 answer
asked
May 8, 2018
by
anonymous
The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be : (A) 34.64 kVA (B) 75 kVA (C) 20 kVA (D) None of the above
Last Answer : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be : 34.64 kVA
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199 views
1 answer
asked
May 8, 2018
by
anonymous
Transformer has __________________ . (A) Primary winding and secondary winding (B) Primary winding and Auxiliary winding (C) Auxiliary winding and secondary winding (D) None of the above
Last Answer : Transformer has Primary winding and secondary winding.
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63 views
1 answer
asked
May 8, 2018
by
anonymous
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
Last 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
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795 views
1 answer
asked
May 8, 2018
by
anonymous
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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 transformer operates 24 hours day at full -load. It's full -load efficiency is : (A) equal all day efficiency (B) more than all -day efficiency (C) less than all -day efficiency (D) equal to maximum efficiency
Last Answer : A transformer operates 24 hours day at full -load. It's full -load efficiency is : equal all day efficiency
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264 views
1 answer
asked
Apr 30, 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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301 views
1 answer
asked
Apr 30, 2018
by
anonymous
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
Last 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
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99 views
1 answer
asked
Apr 29, 2018
by
anonymous
Which of the following is true with an auto transformer? A) It has only one winding B) It has two separate windings namely primary winding and secondary winding C) It has two primary windings and one single secondary winding D) None of these
Last Answer : A it has only one winding.
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527 views
2 answers
asked
Apr 29, 2018
by
anonymous
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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
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94 views
1 answer
asked
Apr 28, 2018
by
anonymous
A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is (A) 216 V (B) 226 V (C) 234 V (D) 236 V
Last Answer : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is 226 V
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139 views
1 answer
asked
Apr 28, 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
The stepup transformer increases?
Last Answer : The stepup transformer increases voltage.
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39 views
1 answer
asked
Mar 26, 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
