Why Transformer Core Loss Can Rise After Assembly

Why can a large core test above its calculated no-load loss? The steel grade may be unchanged, but its stress state can change during production. Uneven support bends lower packets. Tilting redirects loads through the frame, limbs and yokes. Uneven clamping can concentrate pressure instead of spreading it. Grain-oriented steel is sensitive to these mechanical stresses. Loss and noise can rise. Support the full footprint on a rigid stacking table. Use a tilting fixture that supports the core throughout the movement. Check clamp-frame flatness, follow the specified tightening sequence, and record it. Judge the finished core with its agreed tests, alongside the material certificate.