Electrical Transformer Fundamentals and…

Q: What fundamental parameter of an AC circuit remains unchanged when passing through a transformer?

Frequency — A transformer changes the voltage level of an AC circuit without altering the frequency of the power supply.

Q: Why are air core transformers preferred for radio frequency applications?

They eliminate hysteresis and eddy current losses found in iron cores — Air core transformers avoid core losses like hysteresis and eddy currents, which increase with frequency, making them ideal for high-frequency radio applications.

Q: Which material is commonly used to construct the core of a ferromagnetic transformer?

Iron — Iron is a common ferromagnetic material used in transformers to increase magnetic permeability and field strength.

Q: What is the primary advantage of an air core transformer in mobile electronic devices?

Low weight — Air core transformers are lightweight, making them suitable for portable electronic equipment like radio transmitters.

Q: Which type of transformer is specifically designed to change the voltage level to suit power transmission requirements?

Power transformer — Power transformers are used for heavy load applications and are designed for voltage conversion in transmission systems.

Q: What is the main function of an isolation transformer?

To electrically decouple two circuits for safety — Isolation transformers are used to isolate the load from the power source, typically for safety or to reduce noise.

Q: Which of the following is a type of instrument transformer?

Current transformer — Current transformers and Potential transformers are the two main types of instrument transformers used for measurement.

Q: What causes core losses in a ferromagnetic transformer?

Both eddy currents and hysteresis — Ferromagnetic cores suffer from frequency-dependent losses, specifically eddy current losses and hysteresis losses.

Q: What is the primary characteristic of an autotransformer?

It uses a single shared winding for both primary and secondary — An autotransformer features a single winding that acts as part of both the primary and secondary circuits.

Q: Which transformer type is classified based on the insulation medium used?

Oil immersed transformer — Transformers are classified as dry-type or oil-immersed based on the insulation and cooling medium used.

Question 1 of 20

What fundamental parameter of an AC circuit remains unchanged when passing through a transformer?

A transformer changes the voltage level of an AC circuit without altering the frequency of the power supply.

Question 2 of 20

Why are air core transformers preferred for radio frequency applications?

Air core transformers avoid core losses like hysteresis and eddy currents, which increase with frequency, making them ideal for high-frequency radio applications.

Question 3 of 20

Which material is commonly used to construct the core of a ferromagnetic transformer?

Iron is a common ferromagnetic material used in transformers to increase magnetic permeability and field strength.

Question 4 of 20

What is the primary advantage of an air core transformer in mobile electronic devices?

Air core transformers are lightweight, making them suitable for portable electronic equipment like radio transmitters.

Question 5 of 20

Which type of transformer is specifically designed to change the voltage level to suit power transmission requirements?

Power transformers are used for heavy load applications and are designed for voltage conversion in transmission systems.

Question 6 of 20

What is the main function of an isolation transformer?

Isolation transformers are used to isolate the load from the power source, typically for safety or to reduce noise.

Question 7 of 20

Which of the following is a type of instrument transformer?

Current transformers and Potential transformers are the two main types of instrument transformers used for measurement.

Question 8 of 20

What causes core losses in a ferromagnetic transformer?

Ferromagnetic cores suffer from frequency-dependent losses, specifically eddy current losses and hysteresis losses.

Question 9 of 20

What is the primary characteristic of an autotransformer?

An autotransformer features a single winding that acts as part of both the primary and secondary circuits.

Question 10 of 20

Which transformer type is classified based on the insulation medium used?

Transformers are classified as dry-type or oil-immersed based on the insulation and cooling medium used.

Question 11 of 20

What is the function of a Potential Transformer (PT)?

Potential transformers are used to step down high voltages to safe levels for measurement by standard instruments.

Question 12 of 20

How are transformers classified based on the number of phases?

Transformers are categorized by the number of phases they handle, commonly single-phase or three-phase units.

Question 13 of 20

Which of the following is NOT a core design classification mentioned?

Core, Shell, and Berry are core design types; 'Winding type' is a classification based on winding configuration.

Question 14 of 20

What is the primary difference between a step-up and step-down transformer?

Step-up transformers increase voltage, while step-down transformers decrease voltage.

Question 15 of 20

Why is the magnetic permeability of an air core considered low?

Air has very low magnetic permeability, which results in poor flux linkage compared to ferromagnetic cores.

Question 16 of 20

What happens to core losses in iron core transformers if the frequency increases?

Core losses (eddy current and hysteresis) are frequency-dependent and increase as the frequency increases.

Question 17 of 20

Which of the following is most suitable for high-frequency signals?

Air core transformers are preferred at high frequencies because they avoid the distortion and losses associated with ferromagnetic cores.

Question 18 of 20

What is the primary purpose of a Current Transformer (CT)?

Current transformers are instrument transformers used to step down high primary currents to a lower level for safe measurement.

Question 19 of 20

Which type of transformer design uses a core where the windings are surrounded by the core limbs?

In a shell-type transformer, the core surrounds the windings, providing a more robust path for magnetic flux.

Question 20 of 20

What is the main advantage of using a ferromagnetic core in a power supply transformer?

Ferromagnetic cores significantly increase the magnetic field strength, making them efficient for low-frequency power applications.

Electrical Transformer Fundamentals and Classification