Transformer Iron (Core) Loss

Formula

Description

Iron or core loss is the power dissipated in the magnetic core itself, independent of load current. It has two parts: hysteresis loss, from the energy needed to repeatedly reverse the magnetic domains each cycle, and eddy-current loss, from circulating currents induced in the core. Iron loss is essentially constant whenever the transformer is energized, so it dominates the no-load and light-load efficiency.

Variables

• Piron — Total core loss (W)
• Physt — Hysteresis loss (W)
• Peddy — Eddy-current loss (W)

Practical Notes

Laminating the core and using silicon steel or ferrite reduces eddy losses; choosing a low-coercivity material reduces hysteresis loss. Iron loss is measured by the open-circuit test.