In these situations, ferrite solenoid or bobbin inductors are the appropriate choice. When components are densely packed or where EM is a concern, shielded and toroid powdered core inductors are preferred. For EMI suppression, inductors work bi-directionally and are mainly employed in series with a 60Hz power line and input to a switching regulator to prevent unwanted conductive high frequency noise energy from entering the system or feeding back to the main power line. Component selection should be based on current handling capability, radiation and temperature rise characteristics, except that the core loss is significantly less because of low voltage across the inductor. What a circuit needs for EMI suppression is attenuation over a frequency spend, not just on the inductance.
Inductors achieve the highest attenuation at self-resonant frequency.
To gain high attenuation at wide frequency ranges, it is customary to have low and high self-resonant frequency inductors placed in series. Inductor performance is greatly increased by adding capacitors from line to ground, in effect becoming a multi-element EMI filter. In contrast to the energy storage application, high loss core like the high permeability iron powder is an added advantage, since more of the noise energy is being absorbed in this case. When there is an inductor problem, in many instances overheating is typically the first cause to occur due to power loss. High flux density results in high loss.