Transformers MCQs (Part-6)

What is the primary function of a transformer?

A To store energy
B To convert AC to DC
C To change voltage levels in an alternating current (AC) system
D To store electrical energy

What type of transformer is most commonly used in power generation plants to increase the voltage for transmission?

A Step-up transformer
B Step-down transformer
C Distribution transformer
D Isolation transformer

What is the primary cause of energy losses in a transformer?

A Magnetic losses
B Copper losses and core losses
C Voltage regulation
D Cooling inefficiency

Which of the following is a core material used in transformer construction?

A Copper
B Aluminium
C Silicon steel
D Iron oxide

What is the purpose of a transformer’s cooling system?

A To store excess energy
B To keep the transformer at a safe operating temperature
C To prevent voltage regulation issues
D To reduce electrical losses

What is a characteristic of a dry-type transformer?

A It uses oil for cooling
B It uses air for cooling and does not require oil
C It operates at lower voltages
D It is used only for high-voltage applications

What does the turns ratio in a transformer refer to?

A The ratio of the current in the primary and secondary windings
B The ratio of the number of turns in the primary winding to the number of turns in the secondary winding
C The ratio of the transformer’s efficiency
D The ratio of copper losses to core losses

What is the key difference between a single-phase and a three-phase transformer?

A The number of windings used
B The number of phases the transformer is designed to handle
C The size of the core
D The voltage rating

What happens if a transformer is overloaded?

A The voltage decreases
B The transformer becomes more efficient
C The transformer may overheat and fail
D The current is reduced

What is the purpose of a tap changer in a transformer?

A To measure the load current
B To change the turns ratio for voltage regulation
C To maintain the core temperature
D To prevent transformer damage due to short circuits

What is the typical efficiency range of modern transformers?

A 50-60%
B 70-80%
C 90-98%
D 100%

What type of transformer is most commonly used in residential power distribution?

A Step-up transformer
B Power transformer
C Distribution transformer
D Isolation transformer

What is an earthing transformer used for?

A To isolate the primary and secondary circuits
B To provide a neutral point in a system
C To increase voltage
D To reduce harmonic distortion

What is meant by “voltage regulation” in a transformer?

A The ability to adjust the voltage in the transformer
B The ability to maintain a constant voltage despite changes in load
C The efficiency of the transformer
D The method of reducing energy losses

What does “inrush current” refer to in a transformer?

A The current that flows during normal operation
B The sudden surge of current when the transformer is energized
C The current used for cooling
D The current required to magnetize the core

Which of the following is a loss in a transformer?

A Core loss
B Copper loss
C Dielectric loss
D All of the above

What type of cooling method is used in large, high-power transformers?

A Air cooling
B Water cooling
C Oil cooling
D Liquid nitrogen cooling

What is a common method of testing a transformer’s insulation resistance?

A Load test
B Short-circuit test
C Megger test (insulation resistance test)
D Open-circuit test

What is the role of a transformer’s secondary winding?

A To generate magnetic flux
B To transfer power to the load
C To supply current to the primary winding
D To adjust the voltage

What is a parallel operation of transformers used for?

A To share the load between multiple transformers
B To increase the transformer’s efficiency
C To reduce harmonic distortion
D To convert AC to DC