Last Answer : Winding will be damaged
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136 views
2 answers
asked
Mar 19, 2018
by
anonymous
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Last Answer : Necessary conditions required to be satisfied in order to ensure successful parallel operation of single phase transformers: 1. Only transformers having the same phase displacement between primary and secondary ... . 7. The phase sequence must be followed strictly on HV and LV side connection.
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197 views
2 answers
asked
Mar 19, 2018
by
anonymous

Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in?
Last Answer : Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in loading of the transformers not in proportion to their kVA ratings.
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377 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Natural oil cooling is used for transformers up to a rating of 3000 kVA.
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158 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Distribution transformers are generally designed for maximum efficiency around 50% load.
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142 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Power transformers are generally designed to have maximum efficiency around near full-load.
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108 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Short circuit test on transformers is conducted to determine copper losses.
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218 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Natural air cooling is generally restricted for transformers up to 1.5 MVA .
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189 views
1 answer
asked
Mar 19, 2018
by
anonymous

Losses which occur in rotating electric machines and do not occur in transformers are?
Last Answer : Friction losses windage losses
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209 views
2 answers
asked
Mar 19, 2018
by
anonymous

The efficiency of two identical transformers under load conditions can be determined by?
Last Answer : The efficiency of two identical transformers under load conditions can be determined by back-to-back test.
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323 views
1 answer
asked
Mar 19, 2018
by
anonymous
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The efficiencies of transformers compared with that of electric motors of the same power are?
Last Answer : Transformers have high efficiency than the same ratted motors
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179 views
2 answers
asked
Mar 19, 2018
by
anonymous

Two 3-phase transformers cannot be operated in parallel, if their : (A) kVAs are different (B) phase sequences are different (C) % impedances are different (D) voltage ratios are different
Last Answer : Two 3-phase transformers cannot be operated in parallel, if their : phase sequences are different
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151 views
1 answer
asked
Apr 30, 2018
by
anonymous

An additional condition for parallel operation of three-phase transformers over single-phase transformers is that
Last Answer : An additional condition for parallel operation of three-phase transformers over single-phase transformers is that the transformers should belong to the same vector group
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144 views
1 answer
asked
Apr 29, 2018
by
anonymous

Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by
Last Answer : Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by 33%
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674 views
1 answer
asked
May 8, 2018
by
anonymous

Last Answer : A common method of cooling a power transformer is oil cooling.
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156 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : Harmonics in transformer result in increased core losses, increased I2R losses, and magnetic interference with communication circuits.
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70 views
1 answer
asked
Mar 19, 2018
by
anonymous

74)Power transformers are generally designed to have maximum efficiency around A. No load B. Half load C. Near full load D. 10% overload
Last Answer : C. Near full load
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14 views
1 answer

[23] Transformers are rated in KVA instead of KW because A. load power factor is often not known B. KVA is fixed whereas KW depends on load power factor C. Total transformer loss depends on volt ampere D. It has become customary
Last Answer : C. Total transformer loss depends on volt ampere
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130 views
1 answer

TRANSFORMERS MCQ
Last Answer : 101. A shell-type transformer has (a) high eddy current losses (b) reduced magnetic leakage (c) negligibly hysteresis losses (d) none of the above Ans: b 102. A transformer can have regulation closer to zero (a ... (6) much smaller (c) much higher (d) somewhat smaller (e) none of the above Ans: c
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545 views
3 answers

What are the schedules of maintenance done on transformers?
Last Answer : Ans. Following are the schedules of maintenance on transformers. a. Daily maintenance. b. Monthly maintenance. c. Quarterly maintenance. d. Half yearly maintenance. e. Yearly maintenance. f. 5 Yearly maintenance.
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7 views
1 answer

Why a transformer requires cooling. What are the methods of cooling transformers?
Last Answer : Ans. Transformers requires cooling as they get heated up due to various losses taking place in the transformer. (like iron of copper losses) Following are the methods of cooling of transformer. a. Natural ... . Forced oil air Natural Cooling (OFAN). d. Forced oil and forced Air cooling (OFAF).
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7 views
1 answer

What are the loses in Transformers, Explain?
Last Answer : Ans. (1) Iron loses (2) Copper loses Iron Loss : Iron loss occurs in the transformers Iron core due to hysteresis and eddy currents taking place. They are almost fixed irrespective of ... losses in the primary and the secondary windings of the transformer which with the loading of transformer.
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3 views
1 answer

63 views
0 answers
asked
Aug 13, 2019
by
Alacrity

Classify the transformers based on the construction, frequency and power.
Last Answer : Classification of Transformer Based On: i) Construction: Shell type, Core type, Berry type ii) Change in voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) ... Control vi) Cooling: Self-cooled, Air-cooled, Forced-air cooled, Oil-cooled, Forced-oil cooled.
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133 views
1 answer
asked
Aug 30, 2018
by
anonymous

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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581 views
1 answer
asked
May 8, 2018
by
anonymous
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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

In a transmission line if booster transformers are to be used, preferred location will be (A) At the receiving end (B) At the sending end (C) At the intermediate point (D) Anywhere in the line
Last Answer : In a transmission line if booster transformers are to be used, preferred location will be At the intermediate point
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346 views
1 answer
asked
May 8, 2018
by
anonymous
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The friction losses in Real Transformers are : (A) 0% (B) 5% (C) 25% (D) 50%
Last Answer : A
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3.3k views
2 answers
asked
May 8, 2018
by
anonymous

Which of the following is the advantage of using CRGO steel in transformers? A) High magnetic flux density B) Low permeability C) Both A and B D) None of these
Last Answer : It definitely High Magnetic Flux Density since a crgo steel has always a more around 3% of silicon proportion among the remaining ferrite which make cold rolled grain oriented steel having high flux magnetic ... for more about the crgo core you can learn here https://nicoreindia.com/crgo-core/
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154 views
2 answers
asked
Apr 29, 2018
by
anonymous

Last Answer : Instrument transformers are potential transformers, current transformers.
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84 views
1 answer
asked
Mar 21, 2018
by
anonymous

What is the back EMF in Transformers?
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77 views
0 answers
asked
Mar 15, 2018
by
anonymous

Last Answer : Current transformers (CT) : Current transformer (CT) actually step down the high current to low current for the operation of relays. Current transformer is use for measurement of ... use for relay. This is about potential transformer.
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137 views
1 answer
asked
Jan 15, 2018
by
James

Why do transformers make noise?
Last Answer : Transformers make noise based on it out put if an transformer outputs is 400v maximum than a 398v be apply to that transformer it also make a noise because of that
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91 views
1 answer
asked
Dec 17, 2017
by
anonymous

Two transformers of identical voltages but different capacities are operated in parallel, for satisfactory load sharing: a) Impedances should be equal b) Per unit impedance must be equal c) per unit impedance and X/R ratio must be equal d) Impedance and X/R ratio must be equal
Last Answer : Ans: C
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3 views
1 answer

Two transformers with identical voltage ratings are working in parallel to supply common load. The percentage impedance of one transformer is higher compared to that of other. The load sharing ... respective impedance (4) Depend on the resistance to leakage reactance ratio of each transformer
Last Answer : Two transformers with identical voltage ratings are working in parallel to supply common load. The percentage impedance of one transformer is higher compared to that of other. The load sharing between the two transformer will: Be inversely proportional of their respective impedance
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86 views
1 answer
asked
May 22, 2018
by
anonymous

When two transformers are operating in parallel, they will share the load as under: (A) proportional to their impedances. (B) inversely proportional to their impedances. (C) 50% - 50% (D) 25%-75%
Last Answer : Ans: A High rating transformer has higher impedance. kVA rating α Impedance of transformer
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112 views
1 answer

State any two conditions for parallel operation of 3-phase transformer.
Last Answer : Conditions for Parallel operation of 3 phase transformer 1) Voltage ratings of both the transformers must be identical. 2) Percentage or p.u. impedance should be equal in magnitude. 3) X/R ratio ... between primary & secondary voltages must be same. 6) Phase sequence on both sides must be same.
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51 views
1 answer
asked
Jan 8, 2021
by
anonymous

78 Which type of winding is used in 3 phase shell type transformer? A. Circular type B. Sandwich type C. Cylindrical type D. Rectangular type
Last Answer : B. Sandwich type
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35 views
1 answer

73 The full load copper loss of a transformer is 1600W. At half-load the copper loss will be A. 6400W B. 1600W C. 800W D. 400W
Last Answer : D. 400W
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13 views
1 answer

5 The efficiency of a transformer is maximum when A. It runs at half full load B. it runs at full load C. its Cu loss equal iron loss D. it runs over load
Last Answer : C. Its cu loss equal iron loss
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18 views
1 answer

State any two applications of single phase autotransformer.
Last Answer : Applications of single phase auto transformers: 1) Give small boost to distribution cable to correct the voltage drop. 2) As auto transformer starter for induction motors. 3) As furnace supply ... . 5) In control equipment for single phase locomotives. 6) As dimmer in lighting circuits.
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52 views
1 answer
asked
Jan 8, 2021
by
anonymous

Compare core type transformer and shell type transformer on the following parameters. (i) Types of winding used, (ii) Application
Last Answer : Ans:
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52 views
1 answer
asked
Jan 8, 2021
by
anonymous

Define transformation ratio in terms of current and voltage.
Last Answer : (i) Transformation Ratio (K) is defined as the ratio of the primary current to the secondary current. (ii) Transformation Ratio (K) is defined as the ratio of the secondary voltage to the primary voltage.
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41 views
1 answer
asked
Jan 8, 2021
by
anonymous

Define: (i) Commercial efficiency of a transformer and (ii) All day efficiency of a transformer.
Last Answer : (i) Commercial Efficiency : It is the ratio of output power in watt to the input power in watt. (ii) All day efficiency of a transformer: It is the ratio of output energy in kWh to the input energy in kWh in the 24 hours of the day
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136 views
1 answer
asked
Jan 8, 2021
by
anonymous

A 50 KVA transformer has iron loss 2 kW on full load. Calculate its iron loss at 75% of full load.
Last Answer : Iron loss is dependent on voltage and independent of load. Hence iron loss at 75% of Load = Iron loss at full load = 2 kW
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104 views
1 answer
asked
Jan 8, 2021
by
anonymous

State any four properties of Ideal transformer.
Last Answer : Properties of Ideal transformer: 1) No losses (iron and copper losses), hence no temperature rise. 2) No magnetic leakage i.e (Coefficient of coupling between primary and secondary windings is unity) 3) Zero winding ... drop i.e. E1 = V1, E2 = V2 5) Efficiency 100 %. 6) Regulation 0 %.
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34 views
1 answer
asked
Jan 8, 2021
by
anonymous

Draw the connection diagram of long shunt differential D.C. compound generator.
Last Answer : Ans:
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21 views
1 answer
asked
Jan 8, 2021
by
anonymous

2.5k views
0 answers
asked
Jul 24, 2019
by
Deepak kumar bharti

Why circuit breaker connect b)w two transformer (same rating
Last 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.
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113 views
1 answer
asked
Apr 28, 2019
by
Umar Yousaf

Two transformers are to be operated in parallel such that they share load in proportion to their kVA ratings. The rating of the first transformer is 500 kVA ratings. The rating of the first transformer is 500 kVA and its pu ... its pu leakage impedance is (A) 0.20 (B) 0.10 (C) 0.05 (D) 0.025
Last Answer : Two transformers are to be operated in parallel such that they share load in proportion to their kVA ratings. The rating of the first transformer is 500 kVA ratings. The rating of the first transformer is ... .05 pu. If the rating of second transformer is 250 kVA, its pu leakage impedance is 0.10
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260 views
1 answer
asked
May 17, 2018
by
anonymous
