September 18, 2016

12 Most Common Interview Questions and Answers on Transformer - Part 2

Q. 1: What is induction?

A. 1: The process by which one conductor produces, or induces, a voltage in another conductor, even though there is no mechanical coupling between the two conductors.

Q. 2: What is inductance?

A. 2: The property of a coil in a circuit to oppose any change of existing current flow.

Q. 3: What is self-inductance?

A. 3: The inducing of an emf within the circuit itself, caused by any change of current within that circuit. This induced emf is always in a direction opposite to the applied emf, thus causing opposition to any change in current within the circuit itself.

Q. 4: What is mutual inductance?

A. 4: The linkage of flux between two coils or conductors, caused by the current flowing within one or both of the coils or conductors.

Q. 5: Name several methods by which an emf can be generated.

A. 5: By conductors being cut by-
  • A magnetic field (as in generators) 
  • Chemical reactions (as in batteries)
  • Heat (as in thermocouples)
  • Crystal vibration (as in piezoelectricity) and 
  • Friction (as in static electricity).

Q. 6: What is a transformer?

A. 6: A device that transforms electrical energy from one or more circuits to one or more other circuits at the same frequency but usually at a different voltage and current. It consists of a core of soft-iron laminations surrounded by coils of copper-insulated wire.

Q. 7: Draw a diagram of two coils, such as the coils of a transformer winding, and indicate the self-inductance and the mutual inductance.

A. 7: Self-inductance is produced within the primary coil, and mutual inductance exists between the two transformer coils, as shown bellow this Figure:
Self-inductance and mutual inductance in the coils of a Transformer.
Figure: Self-inductance and mutual inductance in the coils of a Transformer.

Q. 8: What always surrounds a conductor when a current flows through it?

A. 8: A magnetic field.

Q. 9: There are two basic types of transformers. What are they?

A. 9: The isolation type, in which the two windings are physically isolated and electrically insulated from each other, and the autotransformer type, in which there is only one coil with a tap or taps taken off it to secure other voltages (the primary is part of the secondary and the secondary is part of the primary).

Q. 10: What is an oil-immersed transformer?

A. 10: The core and coils are immersed in a high-grade mineral oil, which has high dielectric qualities.

Q. 11: What is Transformer Oil?

A. 11: Transformer oil or insulating oil is an oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high-voltage capacitors, fluorescent lamp ballasts, and some types of high-voltage switches and circuit breakers. Its functions are to insulate, suppress corona and arcing, and to serve as a coolant.

Transformer oil is most often based on mineral oil, but alternative formulations with better engineering and/or environmental properties are growing in popularity.

Q. 12:  Why is oil used in a transformer?

A.12: To increase the dielectric strength of the insulation, to keep down the possibility of arcing between coils, and to dissipate heat to the outer case so that the transformer can carry heavier loads without excessive overheating.

  1. Book of Paul Rosenberg
  2. Wikipedia
  3. Internet.
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 12-most-common-interview-question-and answers on transformer


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