1) What is the maximum temperature limit up to which class E insulation can be used?
a. 120 °C
b. 180 °C
c. 50 °C
d. 90 °C
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Answer
Explanation
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ANSWER: 120 °C
Explanation:
No explanation is available for this question!
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2) What is polarisation index?
a. Ratio of 10 minute resistance to one minute insulation resistance
b. Ratio of 1 minute resistance to 10 minute insulation resistance
c. Ratio of 5 minute resistance to 25 minute insulation resistance
d. None of these
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Answer
Explanation
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ANSWER: Ratio of 10 minute resistance to one minute insulation resistance
Explanation:
No explanation is available for this question!
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3) Which measuring is used for the measurement of insulation resistance?
a. Kelvin’s bridge
b. Wheatstone bridge
c. Megger
d. Both (b) and (c)
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Answer
Explanation
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ANSWER: Megger
Explanation:
No explanation is available for this question!
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4) What is the main cause of noise in the transformer?
a. Magnetostriction
b. Mechanical vibration of the tank
c. Mechanical vibration due to lamination
d. Only (a) & (c)
e. All of these
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Answer
Explanation
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ANSWER: All of these
Explanation:
No explanation is available for this question!
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5) Which test is a special type of test performed on the transformers?
a. Partial discharge
b. Temperature rise test
c. Ratio and polarity test
d. Noise level test
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Answer
Explanation
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ANSWER: Partial discharge
Explanation:
No explanation is available for this question!
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6) Which type of insulation is preferred if the maximum temperature is 130°?
a. Class A
b. Class B
c. Class E
d. Class F
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Answer
Explanation
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ANSWER: Class B
Explanation:
No explanation is available for this question!
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7) Which connection is preferred for connecting line tap changers to transformers?
a. 3 wire 3 phase AC system
b. 3 wire 2 phase AC system
c. 4 wire 3 phase AC system
d. All of these
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Answer
Explanation
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ANSWER: 4 wire 3 phase AC system
Explanation:
No explanation is available for this question!
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8) Which among the following safety devices are provided on the power transformers?
a. Marshalling kiosk
b. Vacuum gauge
c. Pressure relief gauge
d. All of these
e. None of these
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Answer
Explanation
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ANSWER: All of these
Explanation:
No explanation is available for this question!
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9) Which cooling system is employed for large transformers?
a. Oil natural oil forced
b. Oil natural air forced
c. Oil forced air forced
d. Both (b) and (c)
e. All of these
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Answer
Explanation
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ANSWER: Both (b) and (c)
Explanation:
No explanation is available for this question!
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10) Which gel ensures the dryness of the incoming air in the breather?
a. Potassium gel
b. Silica gel
c. Carbon gel
d. All of these
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Answer
Explanation
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ANSWER: Silica gel
Explanation:
No explanation is available for this question!
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