Which design choice reduces eddy current losses in a transformer core?

Which design choice reduces eddy current losses in a transformer core?

• A. Non-laminated solid copper core.
• B. Laminated core with high resistivity and proper orientation.
• C. Thicker iron without laminations.
• D. Using air-core only.

Answer: (B)

Eddy current losses come from circulating currents that are induced inside a conducting core whenever the magnetic flux through the core changes. These currents heat the material, and the amount of loss grows with how easily the material conducts (conductivity), how strong and how rapidly the flux changes, and how large the looping paths can be. Using a laminated core made of high-resistivity material and oriented so the laminations lie in the flux path does exactly what cuts those circulating currents down. Thin, insulated layers break up large current loops into many tiny ones, and the insulation between layers adds resistance to those loops. As a result, the eddy currents are smaller and the associated losses are much lower. The material’s higher resistivity also helps reduce the current magnitude for the same changing flux. Putting in solid non-laminated copper would allow very large circulating currents because copper conducts well and there’s nothing to interrupt the loops, causing heavy losses. A thicker iron core without laminations provides even larger loops and far greater eddy currents. An air-core design avoids core losses but isn’t practical for a transformer’s magnetic path and inductance, so it doesn’t address the same issue in typical transformer designs. So, laminated construction with insulating separation and proper orientation minimizes eddy current losses most effectively.

Eddy current losses come from circulating currents that are induced inside a conducting core whenever the magnetic flux through the core changes. These currents heat the material, and the amount of loss grows with how easily the material conducts (conductivity), how strong and how rapidly the flux changes, and how large the looping paths can be.

Using a laminated core made of high-resistivity material and oriented so the laminations lie in the flux path does exactly what cuts those circulating currents down. Thin, insulated layers break up large current loops into many tiny ones, and the insulation between layers adds resistance to those loops. As a result, the eddy currents are smaller and the associated losses are much lower. The material’s higher resistivity also helps reduce the current magnitude for the same changing flux.

Putting in solid non-laminated copper would allow very large circulating currents because copper conducts well and there’s nothing to interrupt the loops, causing heavy losses. A thicker iron core without laminations provides even larger loops and far greater eddy currents. An air-core design avoids core losses but isn’t practical for a transformer’s magnetic path and inductance, so it doesn’t address the same issue in typical transformer designs.

So, laminated construction with insulating separation and proper orientation minimizes eddy current losses most effectively.