Hysteresis and Eddy Current Losses

Hysteresis loss (Steinmetz):

$P_h = k_h f B_{max}^{n} V \qquad (n \approx 1.6\text{–}2)$

proportional to the area of the B–H loop — reduced by using "soft" magnetic materials such as silicon steel.

Eddy-current loss:

$P_e = k_e f^2 B_{max}^2 t^2 V$

where $t$ is the lamination thickness — reduced by building cores from thin insulated laminations (0.23–0.5 mm) or using ferrite at high frequencies. Together these are the core (iron) losses, roughly constant in a transformer at constant voltage.