For given applied voltage, with the increase in frequency of the applied voltagea)eddy current loss will decreaseb)eddy current loss will increasec)eddy current loss will remain unchangedd)none of the aboveCorrect answer is option 'C'. Can you explain this answer?

Question

Answer

Eddy current loss is a type of energy loss that occurs in conductive materials, such as the core of a transformer or the rotor of an electric motor, when they are exposed to a changing magnetic field. The magnitude of eddy current loss is influenced by various factors, including the conductivity and thickness of the material and the frequency of the applied voltage.

When the frequency of the applied voltage increases, the rate at which the magnetic field changes also increases. This can result in an increase in the magnitude of the eddy currents induced in the conductive material. However, at the same time, the skin effect also comes into play.

The skin effect is the tendency of alternating currents to concentrate near the surface of a conductor, with less current flowing through the interior. This effect is more pronounced at higher frequencies. As a result, the effective cross-sectional area available for the flow of eddy currents decreases, leading to a reduction in eddy current losses.

Overall, the increase in frequency tends to increase the eddy currents induced in the material but also decreases the effective area for their flow. These two opposing effects tend to balance each other, resulting in eddy current losses remaining relatively unchanged with an increase in the frequency of the applied voltage.

Therefore, the correct answer is C) eddy current loss will remain unchanged.

Answer

Introduction:
Eddy currents are circulating currents that are induced in a conductor when it is exposed to a changing magnetic field. These currents cause power loss known as eddy current loss. The magnitude of eddy current loss depends on various factors, including the frequency of the applied voltage.

Explanation:
When the frequency of the applied voltage increases, the following effects occur:

1. Increase in Skin Effect:
At higher frequencies, the skin effect becomes more prominent. The skin effect is the tendency of alternating current to concentrate near the surface of a conductor, resulting in a higher current density at the surface. This effect reduces the effective cross-sectional area for current flow, leading to higher resistance and increased eddy current loss. Therefore, the increase in frequency causes an increase in eddy current loss.

2. Decrease in Penetration Depth:
With the increase in frequency, the penetration depth of the magnetic field decreases. The penetration depth is the distance from the surface of the conductor at which the current density is reduced to approximately 37% of its maximum value. As the penetration depth decreases, the magnetic field is concentrated closer to the surface, resulting in a higher current density and increased eddy current loss.

3. Increase in Eddy Current Path Length:
At higher frequencies, the eddy currents have less time to establish their path within the conductor before the direction of the magnetic field changes. This leads to an increase in the path length of the eddy currents, which results in higher resistance and increased eddy current loss.

Conclusion:
Considering the above effects, it can be concluded that with the increase in frequency of the applied voltage, the eddy current loss will increase. Therefore, option 'C' (eddy current loss will remain unchanged) is incorrect, and option 'B' (eddy current loss will increase) is the correct answer.

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