What performance is reflected by the loss tangent (tanδ) of common mode inductance? ​

The tangent of the loss angle (tanδ=Rs/|Xs|) reflects: core loss (hysteresis + eddy current), AC resistance (high-frequency skin effect). For high-quality common mode inductors, tanδ should be less than 0.1 (@1MHz). The larger the tanδ, the greater the energy loss in the core: ① At high frequencies, it can cause inductor heating, reduce efficiency, and even affect reliability due to excessive temperature rise; ② Large loss means a stronger ability to absorb noise energy, but excessive loss may weaken the impedance characteristics of the inductor, thereby reducing the filtering effect. Therefore, it is necessary to balance the tanδ value and find an optimal solution between noise suppression and temperature rise control (high-frequency scenarios usually require low tanδ cores).