The heat caused by iron and copper losses shortens the service life of what materials used in transformer windings?

• A. Insulating materials
• B. Conductors
• C. Core materials
• D. Coolants

Answer: (A)

Heat produced by copper losses in the winding conductors and by iron losses in the core raises the winding temperature. The insulating materials between turns and layers, and between the winding and other parts, are rated for a maximum temperature. When that limit is exceeded, the insulation ages faster: its polymers fracture slowly, moisture is absorbed, dielectric strength drops, and mechanical properties degrade. All of this shortens the insulation’s ability to withstand voltage and separate windings, so the winding’s service life is limited by the insulation aging. The conductors and core are not the primary life-limiting parts in this heating scenario—the insulation’s response to heat is the critical factor.