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Transformers Multiple Choice Questions | MCQs | Quiz

Transformers Interview Questions and Answers
Practice Transformers questions and answers for interviews, campus placements, online tests, aptitude tests, quizzes and competitive exams.

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•   ↓ Transformers ↓
•   Transformer Basic Materials
•   Core Construction
•   Winding Construction
•   Cooling Techniques
•   No Load Operations
•   Ideal Transformer
•   Real Transformer
•   Approximate Circuit
•   Equivalent Phasor Diagrams
•   Transformer Losses
•   Transformer OC Test
•   Transformer SC Test
•   Sumpner's Test
•   Efficiency
•   Voltage Regulation - 1
•   Voltage Regulation - 2
•   Excitation Phenomenon
•   Autotransformer
•   Variable Frequency
•   ↓Three Phase Transformer↓
•   Construction
•   Connections
•   Three Phase Bank
•   3 Phase Transformers Tests
•   Transformer Additional Test
•   Transformer Installations
•   Parallel Operations
•   Transformers Load Division
•   Three Winding Transformers
•   Phase Conversion
•   Tap Changing Transformer-1
•   Tap Changing Transformer-2
•   ↓ Transformers ↓
•   Voltage & Current
•   Audio Frequency
•   Grounding & Welding
•   Transformers - Circuits
•   Neutral Earthing
•   Transformers Noise
•   Transformer Protection
•   Transformer Maintenance
•   Abnormal Conditions
•   Power Station Transformers
•   HVDC Conversion
•   Distribution Transformers

Best Reference Books

Transformers Books
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Transformers Questions and Answers – Operation under Abnormal Conditions

Posted on January 18, 2018 by Manish

This set of Transformers online test focuses on “Operation under Abnormal Conditions”.

1. Increased transformer insulation stresses are due to _______________
a) third harmonic currents
b) third harmonic voltages
c) fifth harmonic currents
d) fifth harmonic voltages
View Answer

Answer: b
Explanation: Following are the effects due to third-harmonic voltages: Increased transformer insulation stresses, electrostatic charging of adjacent lines and telephone cables, possible resonance at third-harmonic frequency of transformer windings and line capacitance.
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2. Overheating of transformer windings and of load are due to ________
a) third harmonic currents
b) third harmonic voltages
c) fifth harmonic currents
d) fifth harmonic voltages
View Answer

Answer: a
Explanation: Following are the effects due to third-harmonic currents: Overheating of transformer windings and of load, telephone and discriminative protective gear magnetic disturbances, increased iron loss in transformers.

3. Operation other than rated power will lead to ______________
a) increase in temperature
b) decrease in temperature
c) short circuit
d) open circuit
View Answer

Answer: a
Explanation: Operation at other than rated load will result in hot-spot temperature rises differing from those corresponding to rated conditions and rated temperature rise is based on a hot-spot temperature of 98°C with a 20°C ambient.

4. Time required for an insulation to reach at end is given by __________________
a) Kirchhoff
b) Joule
c) Ampere
d) Arrhenius
View Answer

Answer: d
Explanation: Expressed in quantitative terms the time required for insulation to reach its end of life condition is given by the Arrhenius law of chemical reaction rate. Within a limited range of temperatures this can be approximated to the simpler Montsinger relationship.
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5. Arrhenius law is given by ___________________
a) L=αβT
b) L=αβ/T
c) L=α+βT
d) L=α+β/T
View Answer

Answer: d
Explanation: L is defined as the time for the reaction to reach a given stage, but which might in this case be defined as end of life, while α and β are constants. T is absolute temperature. In limited range of temperatures, it can be approximated to Montsinger relationship.

6. Rate of aging is __________________
a) v= M e-pθ
b) v= M epθ
c) v= M θe-pθ
d) v= M e-θ
View Answer

Answer: b
Explanation: Montsinger relationship is defined as L= e-pθ , where p is a constant, θ is the temperature in degrees Celsius. Investigators have not always agreed on the criteria for which L is representative of end of life, but for the purposes of this evaluation this is not relevant and of more significance is the rate of ageing. This is the inverse of the lifetime.

7. Relative age rating is ___________________
a) 2(θ – 98) * 6
b) 2(θ – 98) – 6
c) 2(θ – 98) / 6
d) 2(θ – 98)
View Answer

Answer: c
Explanation: If 98°C is then taken as the temperature at which normal ageing rate occurs, then the relative ageing rate at any other temperature θ is given by the expression:
V= ageing rate at θ/ ageing rate at 98°C= 2(θ – 98) / 6
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8. Hot-spot temperature is dependent on ____________
a) 4 categories
b) 6 categories
c) 8 categories
d) 10 categories
View Answer

Answer: a
Explanation: Hot-spot temperature is made up of the following components: Ambient temperature, top oil temperature rise, average gradient, difference between average and maximum gradient of the windings.

9. In 4-wire star connection 3rd harmonic currents may flow through ______________
a) lines
b) phases
c) from fourth wire to neutral
d) all connections
View Answer

Answer: d
Explanation: With a four-wire star connection, third-harmonic voltages from lines to neutral or earth are suppressed partially or completely according to the impedance of the third-harmonic circuit. With a four-wire star connection, third-harmonic currents may flow through the phases and through the line wires and fourth wire from the neutral.

Sanfoundry Global Education & Learning Series – Transformers.

To practice all areas of Transformers for online tests, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Transformers Questions and Answers – Generator and Power Station Transformers »
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Deep Dive @ Sanfoundry:

  1. Microwave Engineering Questions and Answers
  2. Electrical Measurements Questions and Answers
  3. Electrical Machines Questions and Answers
  4. Transformers Questions and Answers
  5. Transformers Questions and Answers – Transformer Construction (Winding)
  6. Transformers Questions and Answers – Generator and Power Station Transformers
  7. Transformers Questions and Answers – Voltage and Current Transformers
  8. Transformers Questions and Answers – Grounding and Welding Transformer
  9. Electrical Measurements Questions and Answers – Advantages of Instrument Transformers
  10. Transformers Questions and Answers – Parallel Operation of Transformers
Manish Bhojasia
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Facebook | Twitter

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