Electrical transformers play a crucial role in transmitting and distributing electrical energy. They enable the efficient transfer of electrical energy between circuits, allowing power to be sent over long distances and voltage levels to be adjusted. Transformers work on the principles of electromagnetic induction and consist of two or more coils of wire wound around a common magnetic core. They can step up or down the voltage levels of alternating current and offer significant advantages in terms of electrical isolation and safety. Transformers come in various sizes and configurations to suit different applications. They are indispensable devices in modern electrical systems, contributing to the reliable and safe delivery of electricity. ElectricalEngineeringOnline.com shares the top 10 objective multiple choice questions on Transformers with brief explanatory answers.
Electrical transformer operates on the principle of
Electrical transformer works on the principle of
- Electromagnetic induction
- Ohm’s Law
- Kirchhoff’s Law
- Joule’s Law
Correct Answer: 1. Electromagnetic induction
Explanation: An electrical transformer operates based on the principle of electromagnetic induction, which involves the generation of the magnetic field as well as induction of current in a secondary winding.
The primary function of a transformer is
The primary part of a transformer is
- Voltage regulation
- Current regulation
- Power factor correction
- Energy transfer
Correct Answer: 4. Energy transfer
Explanation: The primary function of a transformer is to transfer electrical energy from one circuit to another, either by stepping up or down the voltage levels.
The type of transformer used to increase voltage levels
The type of transformer used to increase voltage levels
- Step-up transformer
- Step-down transformer
- Autotransformer
- Distribution transformer
Correct Answer: 1. Step-up transformer
Explanation: A step-up transformer increases the voltage level from a lower to a higher value, typically used in power transmission systems.
The purpose of the tap changer in a transformer is
The purpose of the tap changer in a transformer is
- To control the winding resistance
- To adjust the core material
- To regulate the output voltage
- To increase the power factor
Correct Answer: 3. To regulate the output voltage
Explanation: The tap changer allows for adjusting the turns ratio, enabling the output voltage regulation to compensate for variations in the input voltage or load conditions.
The type of transformer has a single winding and provides a variable voltage output.
The type of transformer has a single winding and provides a variable voltage output
- Step-up transformer
- Step-down transformer
- Isolation transformer
- Autotransformer
Correct Answer: 4. Autotransformer
Explanation: An autotransformer has a single winding with a tap that can be adjusted to provide a variable voltage output, commonly used for voltage regulation in electrical systems.
What is the typical frequency used in power transformers
What is the standard frequency used in power transformers
- 50/60 Hz
- 40/50 Hz
- 50/70 kHz
- 60/80 kHz
Correct Answer: 1. 50/60 Hz
Explanation: Power transformers in electrical grids typically operate at 50 Hz or 60 Hz, depending on the region.
The efficiency of an ideal transformer is
The efficiency of an ideal transformer is
- 50%
- 75%
- 100%
- 125%
Correct Answer: 3. 100%
Explanation: An ideal transformer has no losses and, therefore, operates at 100% efficiency, meaning all the electrical energy supplied to the primary winding is transferred to the secondary winding.
The primary type of losses in a practical transformer is
The primary type of losses in a practical transformer is
- Hysteresis losses
- Eddy current losses
- Copper losses
- Dielectric losses
Correct Answer: 3. Copper losses
Explanation: Copper losses, also known as I^2R losses, occur because of resistance of the windings, causing energy to be dissipated in the form of heat.
The type of transformer that is used to measure high voltage and current accurately
The type of transformer that is used to measure high voltage and current accurately
- Power transformer
- Distribution transformer
- Instrument transformer
- Autotransformer
Correct Answer: 3. Instrument transformer
Explanation: Instrument transformers, such as current transformers (CTs) and voltage transformers (VTs), are specifically designed to measure high voltage and current levels accurately.
What is the purpose of the conservator tank in an oil-filled transformer
What is the goal of the conservator tank in an oil-filled transformer
- To cool the transformer
- To store excess oil
- To reduce oil leakage
- To compensate for oil expansion and contraction
Correct Answer: 4. To compensate for oil expansion and contraction
Explanation: The conservator tank in an oil-filled transformer accommodates the insulating oil’s expansion and contraction as the temperature changes.
The commonly used cooling method for large power transformers
The widely used cooling method for large power transformers
- Air cooling
- Oil cooling
- Water cooling
- Forced-air cooling
Correct Answer: 2. Oil cooling
Explanation: Oil cooling is widely used for large power transformers as it provides efficient heat dissipation and helps maintain optimal operating temperatures.
The function of the Buchholz relay in a transformer
The role of the Buchholz relay in a transformer
- Overload protection
- Overvoltage protection
- Short circuit protection
- Detection of internal faults
Correct Answer: 4. Detection of internal faults
Explanation: The Buchholz relay is a protective device installed in oil-filled transformers to detect internal faults, such as insulation failure or gas accumulation.
Which insulation material is commonly used in high-voltage transformers
Which insulation material is widely used in high-voltage transformers
- Paper
- Rubber
- PVC
- Fiberglass
Correct Answer: 1. Paper
Explanation: Paper is a widely used insulation material in high-voltage transformers due to its high dielectric strength and ability to withstand high temperatures.
What is the purpose of the neutral grounding transformer
What is the purpose of the neutral grounding transformer
- To protect against electrical faults
- To balance the voltage across phases
- To step up the voltage
- To regulate the frequency
Correct Answer: 2. To balance the voltage across phases
Explanation: A neutral grounding transformer balances the voltage across phases in a three-phase electrical system by providing a neutral point for connection.
Which international standard governs the specifications and testing methods for transformers?
Which international standard governs the specifications and testing methods for transformers?
- IEC 60076
- IEEE 1547
- ANSI C84.1
- UL 508
Correct Answer: 1. IEC 60076
Explanation: IEC 60076 is the international standard that governs the specifications, design, and testing methods for power transformers, widely recognized and followed in the industry.