Transformers are essential devices in electrical power systems, and understanding their operation is crucial. Electrical Engineering XYZ MCQs on Transformers aims to test your knowledge of transformers. A transformer is an electromagnetic device that transfers electrical energy between two or more circuits through mutual induction. It consists of two or more coils, called windings, which are linked by a common magnetic core. MCQs on transformers cover various aspects, such as the working principle, types of transformers, voltage regulation, efficiency, and losses. By going through these MCQ based questions, you can evaluate your understanding of transformers and enhance your knowledge of their functioning in power systems.
- 1 Auto-transformer is recommended for the transformation ratio
- 2 From no load to full load condition, the Iron losses in real transformer
- 3 The Eddy losses in a transformer depends on
- 4 Scott connection in transformers are used when
- 5 The PF of the transformer
- 6 The transformer oil should have
- 7 Which of following will be the smallest transformer
- 8 Which one of following is a step-up transformer dealing with high frequency
- 9 The primary winding of a transformer can be considered as
Auto-transformer is recommended for the transformation ratio
Auto-transformer is recommended for the transformation ratio:
Correct answer: 3. 1.1 is the right answer.
Explanation: An autotransformer is used for smaller transformation ration. e.g 21 kV to 21.5 kV stepping is required.
From no load to full load condition, the Iron losses in real transformer
From no load to full load condition, the Iron losses in real transformer:
- Remain constant
- Increase upto 25% of orginal losses
- Decrease by 13% of original losses
- None of these
Correct answer: 1. Remain constant
Explanation: The iron losses depend on the core flux which remains constant from no load to full load.
The Eddy losses in a transformer depends on
The Eddy losses depends on:
- Flux density
- All of these
Correct answer: 4. All of these
Explanation: The formula of Eddy current losses is: P = kef2Bmax2τ2
The correct answer to the multiple-choice question is “All of these.” The Eddy losses in a magnetic material depend on frequency, flux density, and thickness.
Eddy currents are induced circulating currents that occur in conductive materials when exposed to a changing magnetic field. These currents generate heat due to the resistance of the material, leading to power loss known as Eddy losses. Let’s examine how each of the factors mentioned in the question affects Eddy losses:
- Frequency: The magnitude of eddy currents is directly proportional to the frequency of the changing magnetic field. Higher frequencies result in stronger eddy currents, leading to increased power loss.
- Flux density: Eddy losses are also influenced by the flux density, which refers to the strength of the magnetic field. Higher flux densities result in stronger eddy currents and, consequently, increased power loss.
- Thickness: The thickness of the conductive material impacts the magnitude of the eddy currents and, therefore, the Eddy losses. Thicker materials offer more resistance to the flow of eddy currents, resulting in reduced power loss compared to thinner materials.
Therefore, all three factors – frequency, flux density, and thickness – play a role in determining the magnitude of Eddy losses.
Scott connection in transformers are used when
Scott connection in transformers are used when:
- Three-phase to two-phase transformation is required
- Single-phase to two-phase transformation is required
- Three-phase to two and three-phase transformation is required
- For all of these
Correct answer: 2. Three-phase to two and three-phase transformation is required
The PF of the transformer
The PF of the transformer:
- Depends on load
Correct answer: 4. Depends on load
Explanation: The PF depends on PF of the connected load
The transformer oil should have
The transformer oil should have:
- Low viscosity and Low volatility
- Low viscosity and High volatility
- High viscosity and Low volatility
- High viscosity and High volatility
Correct answer: 1. Low viscosity and Low volatility
Explanation: Viscosity is the resistance against friction, whereas volatility is the tendency to vaporize a good oil should have low viscosity as well as low volatility.
Which of following will be the smallest transformer
Figure the smallest transformer:
- 5 kVA, 1000 Hz
- 5 kVA, 2000 Hz
- 5 kVA, 3000 Hz
- 5 kVA, 4000 Hz
Correct answer: d. 5 kVA, 4000 Hz
Explanation: Size of transformer is inversely proportional to the frequency.
Which one of following is a step-up transformer dealing with high frequency
Which one of following is a step-up transformer dealing with high frequency:
- Tesla coil
- None of these
Correct answer: 3. Tesla coil is the right answer
Explanation: Among the options provided, a Tesla coil is the step-up transformer that deals with high frequency.
A Tesla coil is a type of electrical resonant transformer circuit invented by Nikola Tesla in the late 19th century. It is designed to produce high-voltage, high-frequency alternating current (AC) electricity. Tesla coils are typically used for experiments, demonstrations, and in some cases, wireless power transmission.
In a Tesla coil, the primary coil is connected to a power source, typically a high-frequency AC source. The secondary coil, consisting of many turns of wire, is wound around the primary coil. The primary coil induces a high-voltage, high-frequency current in the secondary coil through the process of electromagnetic induction. This leads to a step-up transformation of the voltage, with the secondary coil producing much higher voltages than the input.
Therefore, a Tesla coil is the step-up transformer that deals with high frequency among the options provided. The other options, CT (Current Transformer) and PT (Potential Transformer), are typically used for measuring current and voltage, respectively, in low-frequency power systems.
The primary winding of a transformer can be considered as
The primary winding of a transformer can be considered as:
- A powered inductor
- A powered capacitor
- Both of these
- None of these
Correct answer: a. A powered inductor
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