Iron Powder Core 5A 10A High Current Inductor For Industrial EMI Filter

Toroidal differential mode inductor for the input filter stage of industrial power equipment. Differential mode noise travels down one line and returns on the other, generated by the converter's own switching current. A common mode choke cannot remove it, because a common mode choke is designed to cancel exactly this opposing current. A dedicated differential mode inductor is required to pass conducted emission testing in the lower frequency band.

The core is a toroidal powder core with a single winding of heavy gauge enamelled copper wire. The single winding is the key difference: a common mode choke has two windings whose fields cancel, so its core sees almost no net flux from load current. Here the full line current flows through one winding, so the core must carry real DC and low frequency flux without saturating. That is why a distributed air gap powder core is used instead of high permeability ferrite or nanocrystalline, which would saturate immediately at the same current.

In the finished filter the inductor forms an LC low pass network with the X capacitors: the inductor blocks high frequency switching current from reaching the mains, the capacitors give it a low impedance return path inside the equipment. Inductance value sets the corner frequency, and therefore the attenuation achieved at the failing frequencies.

Made to order. Inductance, rated current, core material, wire gauge, turn count, lead length and lead spacing are all defined against your drawing or the measured emission problem.

Note: inductance, rated current, core material, outer diameter, turn count and wire gauge are defined per application. Approval drawings and samples are issued for your confirmation before mass production.

Single winding designed to carry full load current. The core material and turn count are selected so that the inductance holds up under the actual DC and low frequency bias present on the line, rather than collapsing the moment the equipment reaches full load. An inductor that saturates at working current provides no filtering when it is most needed.

Soft saturation powder core. The distributed gap inside a powder core produces a gradual inductance roll off instead of a sharp saturation knee. Filtering performance degrades smoothly during inrush and load steps rather than disappearing, which keeps emission behaviour predictable across the full operating range.

Closed toroidal magnetic path. Flux stays inside the ring, so the inductor radiates very little stray field into surrounding traces and sensitive analogue circuitry. This is a direct advantage over gapped bobbin designs, where the gap becomes a local radiator that then has to be shielded.

Low loss at switching frequency. Core material is chosen against the customer switching frequency and ripple current, so core loss and copper loss are balanced at the real operating point instead of at a catalogue condition.

Mechanically stable construction. The winding is varnish impregnated so turns do not shift under vibration or thermal cycling. Stable geometry means stable inductance, which means the filter corner frequency stays where the design placed it over the life of the equipment.

Compact radial format. The toroidal geometry and radial lead termination give a high inductance to volume ratio and a small board footprint, which is useful where the EMI filter has to fit into an already committed layout.

Engineered against your emission data. If you provide the failing frequency and the margin required, we can propose the inductance value rather than asking you to guess it.

• Industrial switching power supply input EMI filter stages
• Solar inverters and energy storage power conversion systems
• Uninterruptible power supplies and industrial backup power
• Motor drives, servo drives and variable frequency drive input filters
• Industrial LED lighting power modules
• Welding equipment and industrial heating power supplies
• Telecom and server rectifier modules
• Frequency converters and industrial automation power sections
• Test and measurement equipment requiring a clean supply
• Medical and laboratory equipment with strict emission limits

The component is normally installed in the AC input line immediately after the fuse and the common mode choke, working with X capacitors to form a complete differential mode filter section. In DC applications it is used in series with the supply rail to suppress ripple and switching noise.