1. Part of the transformer which undergoes most damage from overheating is ___________
a) Iron core
b) Copper winding
c) Winding insulation
d) Frame or case
Explanation: Copper windings carry current through them. The heat loss producing in any winding carrying current is proportional to the square of the current passing through it multiplied with resistance. For large transformers, current is very high, so heating causes most of the damage to insulation material
2. If a transformer is continuously operated the maximum temperature rise will occur in ___________
a) Core
b) Windings
c) Tank
d) Cannot be determined
Explanation: Copper windings carry currents in a transformer. The loss in form of heat in copper winding carrying current is proportional to the square of the current passing through them multiplied by the resistance of the winding. This loss is dissipated in heat and corresponding temperature rise.
3. If secondary number of turns are higher then, transformer is called _________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer
Explanation: When secondary number of turns are higher compare to primary, voltage induced in secondary windings will obviously high. Thus, this transformer is used for stepping up the output voltage by keeping frequency constant.
4. If primary number of turns are higher then, transformer is called _________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer
Explanation: When primary number of turns are higher compare to secondary, voltage induced in secondary windings will obviously low compare to primary. Thus, this transformer is used for stepping down the output voltage by keeping frequency constant.
5. If a transformer is having equal number of turns at primary and secondary then transformer is called as _______________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer
Explanation: A transformer is having equal number of turns at primary and secondary then transformer is called as one-one transformer. This transformer have turns ratio equal to 1, so is the voltage ratio for the one-one transformer.
6. One to one transformers are used because ______________
a) To isolate any part of circuit electrically
b) To get more voltage at secondary
c) To get less voltage at secondary
d) To reduce losses, present in circuit
Explanation: In one to one transformers, we have same number of turns in primary and in secondary. So, increasing/ reducing voltage is not possible. They are generally used to isolate one part of circuit from another part of circuit, electrically
7. Same type and kind of insulations are not used in all types of transformers.
a) True
b) False
Explanation: The windings of huge power transformers use conductors with heavier insulation and are assembled with greater mechanical support and the winding layers are insulated from each other, this is known as minor insulation for which pressed board or varnished cloth is used. While for major insulation and insulating cylinders, they are made of specially selected pressed board or synthetic resin bounded cylinders, is used between LV and core and LV and HV.
8. Sandwiched type of winding is used in ____________
a) In all transformers
b) In core type transformers
c) In shell type transformers
d) In all transformers except shell and core type transformers
Explanation:According to the construction of transformers core type transformers don’t require sandwiched wiring. While, in the shell type transformer, the primary and secondary windings pass inside the steel magnetic circuit (core) which forms a shell around the winding.
9. Which is the most common, famous and adopted method of cooling of a power transformer?
a) Air blast cooling
b) Natural air cooling
c) Oil cooling
d) Any of the above method can be used
Explanation: Oil acts as a best coolant material, for transformer cooling. Due to its high efficiency as a coolant it is most widely used in transformers. Not only same but Oil with suitable properties can be used for various power transformers according to their ratings
10. Function of conservator in an electrical transformer is __________
a) Supply cooling oil to transformer in time of need
b) Provide fresh air for cooling the transformer
c) Protect the transformer from damage when oil expends due to heating
d) Cannot be determkned
Explanation: When transformer is loaded and when ambient temperature rises, the volume of oil inside transformer increases as oil expands. A conservator tank properly installed on transformer provides required space to this expanded transformer oil. It performs another function as a reservoir for transformer insulating oil.