Question

Transformer cores are laminated to reduce

• A. copper loss
• B. hysteresis loss
• C. friction loss
• D. eddy current loss

Hint:

Remember: Laminations target Eddy currents (by breaking the path). Soft iron/Silicon steel targets Hysteresis (by reducing magnetic friction).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A transformer works on alternating magnetic fields. These fields induce circulating currents within the conductive iron core itself, leading to energy loss in the form of heat.

Step 2: Detailed Explanation:
Eddy currents are loops of electrical current induced within conductors by a changing magnetic field. In a solid transformer core, these currents have a large area to flow, causing significant "Eddy current loss." To prevent this, the core is made of thin sheets (laminations) insulated from each other. This breaks the large circular paths into much smaller loops, significantly increasing resistance to these currents and reducing total power loss.

Step 3: Final Answer:
Transformer cores are laminated to reduce eddy current loss.

Answer 2

A transformer core suffers from several distinct kinds of energy loss, and laminating the core is a very specific fix aimed at only one of them. Looking at what each loss type actually is shows why.

1. Copper loss: This loss occurs in the copper windings themselves, caused by their electrical resistance heating up as current flows through them (\(I^2R\) loss). It has nothing to do with the iron core's construction, and is instead reduced by using thicker wires or better conducting material.
2. Hysteresis loss: This loss comes from repeatedly magnetizing and demagnetizing the core material as the alternating current cycles, which absorbs energy as the material's internal magnetic domains realign. It is reduced by choosing a core material with a narrow hysteresis loop (like silicon steel), not by cutting the core into layers.
3. Friction loss: Friction loss applies to machines with moving mechanical parts, like motors or generators with rotating shafts and bearings. A transformer has no moving parts at all, so this type of loss doesn't even apply to it.
4. Eddy current loss: Changing magnetic flux inside a solid conductive core induces circulating currents (eddy currents) within the core material itself, which dissipate energy as heat. Slicing the core into thin, mutually insulated laminations breaks up the large area these currents would otherwise flow through, forcing them into much smaller loops and sharply raising their resistance, which is exactly what lamination is designed to reduce.

Only one of these four loss mechanisms is specifically tied to current loops circulating within the bulk of the core material, and that is precisely the loss laminated construction is meant to fight.

Therefore, the correct answer is eddy current loss.