AC Power Line EMI Filters and Filtered Inlets
A power-line EMI filter is an assembly designed to attenuate conducted interference on a specified electrical supply, usually using common-mode and differential-mode filtering elements. In this collection the core products are single-phase and three-phase AC line filters, IEC filter inlets and related audio power accessories. The listings also include discrete magnetic parts and a few unrelated cables and connectors. Choose the exact option by circuit topology, rated conditions and verified documentation, not by the words “power purifier.”
AC line-filter formats
- Single-phase terminal and wired filters: CW1B and CW4L2 listings have model-dependent 1 A through 30 A choices, with T, S or R suffixes indicating distinct physical styles in shared menus. Check the selected part's 115/230/250 V AC rating, operating frequency, screw or wire terminals, mounting footprint, leakage and protective-earth arrangement. A high-current CW4E option in a mixed CW4L2 listing is a different model.
- Filtered IEC inlets: CW1D, CW2B, CW2C and panel-mount inlet listings integrate a supply connector and may offer a lighted switch or fuse feature. Verify the actual IEC mating interface, inlet current, panel cutout, earth contact and whether the selected version contains a switch, fuse holder or fuse. A plain connector is not a filtered inlet merely because it appears nearby.
- Three-phase industrial filters: FN351-labelled and CW12BL2-labelled entries, plus 380/520 V-class motor filter listings, target different three-phase supply arrangements. Confirm three versus four conductors, actual voltage and frequency, current, terminal spacing, enclosure and verified attenuation curve; a product title mentioning AC/DC does not establish a DC rating or genuine manufacturer origin.
- Open AC filter boards: the 6 A/25 A two-stage audio boards and PCB modules need their own enclosure, insulation, protective-earth and compliance evaluation. An exposed board must not be treated as an approved drop-in alternative to an enclosed line filter.
- Filtered power strips: TP80, e-TP40E, e-TP60 and other EU/US outlet listings are complete outlet accessories, not industrial line-filter modules. Match the country-specific plug and receptacle, actual mains rating, total load and separately documented surge features. “HiFi,” “isolation,” “lightning protection” or a display does not establish measurable attenuation, galvanic isolation or surge capability.
Parts to keep distinct
Clip-on ferrite cable clamps and 4-pin common-mode chokes are suppression components rather than ready-to-install mains filter assemblies. Check ferrite impedance versus frequency, inner diameter or choke inductance, winding pinout, resistance, current and temperature. The LFD707010-labelled DC common-mode part must not be wired as a mains filter without suitable documented ratings. A terminal junction block, JST-XH battery balance lead, M24 waterproof circular connector and solar conversion cable are connection parts, not line filters. They remain among the listings but must be selected for their own separate functions.
How to select
- Locate the noise path and identify whether the supply is single-phase AC, three-phase AC, low-voltage DC or a cable carrying interference. Determine whether you need a finished filter, filtered inlet, outlet strip or a component to design into a circuit.
- Match the equipment's nominal and maximum voltage, phase and conductor count, continuous and transient current, frequency, ambient temperature, protective-earth and allowable leakage. Do not infer these values from a model family or a neighboring variant.
- Assess common-mode and differential-mode insertion loss across the relevant frequency band using a traceable datasheet. Results depend on source/load impedance, grounding and layout; a “two-stage” label by itself cannot predict an audio or EMC outcome.
- Check the actual mechanical interface: panel cutout, IEC inlet and mating cord, terminal cover, rail or bolt mount, case dimensions and thermal clearance. For a strip, check outlet and plug standards plus total load.
- Seek model-specific documentation for safety approval, leakage, insulation, surge or brand-provenance claims. Generic CE/RoHS text, “medical grade” or “genuine” in a seller title is not evidence applicable to every offered option.
Buying checklist and applications
Record the original equipment specification, supply type, conductor count, voltage and current, target interference frequencies, leakage limit, earthing, insertion-loss conditions, connections, mounting and exact package contents. Industrial drive and power-supply installations have different requirements from home audio outlets. Mains installation should follow equipment documentation and qualified electrical practice; this page does not provide general line-wiring instructions.
Frequently asked questions
Can a three-phase filter replace a single-phase IEC inlet?
No. Match supply topology, conductor count, voltage, rated current, earth path and connector arrangement.
Will an AC line filter remove every audio hum?
No. Hum can arise from grounding, signal interconnections, magnetic coupling or power design. A line filter's specified attenuation concerns conducted interference under defined conditions.
Does an EMI-filtered power strip automatically protect against lightning?
No. Surge protection is separate from conducted-noise filtering. Check documented protection for the selected strip.
Is a 5 mH choke a complete line filter?
No. The winding is one component, and its inductance alone cannot specify a completed filter's safety or attenuation.
