EMI/RFI Filters

What is an EMI/RFI Filter?

EMI (Electromagnetic Interference) Filters, also called RFI (radio-frequency interference) Filters, are an electrical device / circuit that mitigate the high frequency Electromagnetic noise present on the power and signal lines. The high frequency noise is generated by a variety of electrical and electronic devices such as motors, electronic controls, power supplies, inverters, clock circuits, microprocessors, appliances, electronic devices etc. This noise is typically in the 9KHz to 10GHz frequency range and it can degrade or prevent the signal transmissions and/or the intended performance of an electrical/electronic equipment. The lower frequency components of the EM noise can impact the power quality as well.

The Industrial EMI/RFI Filter provides a low impedance path to the high frequency noise and reduces it by either cancelling its line and neutral components or by grounding it. The effectiveness of an EMI/RFI filter measure as insertion loss (in dB over the frequency range). An EMI Filter is usually most useful for the Electromagnetic noise is 9KHz to 30MHz frequency range which is conducted through the wires. The frequencies beyond 30MHz are typically radiated (travel through the air) requiring shielding and input/output isolation. For radiated frequencies, the filter mounting is more critical than its insertion loss performance.

EMI/RFI filters are widely used in applications such as Appliances, Military/Aerospace systems & subsystems, Energy Management Systems, Computers, Factory Automation Equipment, Industrial Equipment, Medical Imaging/Diagnostic/Patient Devices, Exercise Equipment, Automotive Battery Charger, MRI Rooms, Test Chambers/Shielded Rooms and many others.


At Radius Power, we offer a complete selection of standard (off the shelf) Power line, IEC Inlet, MIL-COTS, TEMPEST EMI filters for DC, single phase and 3-phase AC (delta and wye) applications. Our EMI / EMC / RFI Filter solutions, range from small 1A single phase or DC EMI filter to high-power 2500A / 690VAC industrial 3-phase EMI filters and 2500A / 1200VDC EMI filters for inverter applications. Most of our standard catalog items carry international approvals (UL, cUL/CSA, IEC/EN/CE).

Our full range of Standard solutions can be easily customized to meet customer-specific requirements and to help our customers meet all the international compliance standards. With our in-house agency approval capability, even our customized and fully custom product can be supplied with full agency approvals for US, Canada and Europe, if required, making it easy for end user’s equipment to meet the EMI immunity and safety standards.

Our extensive line of standard and custom EMI Filters address all disciplines from DC EMI Filters to Single Phase and Three Phase EMI Filters.

For Medical Applications, our entire IEC Inlet/Power Entry Modules, single phase and three phase EMI filters are available as Medical Grade EMI Filters to comply with both patient and nonpatient low-leakage current requirements for medical equipment. Our Telecom EMI Filters encompass all AC/DC power networks and are designed to meet all applicable standards such as NEBS, CE, etc.

Our COTS line of standard and custom Military EMI Filters provides solutions for MIL-STD-461, RTCA/DO-160 and Tempest for land, shipboard and airborne environments.

Additionally, our Inverter EMI Filters provide cost effective solutions for industrial machinery, VFDs, drives, solar and wind with the best lead times in the industry.

At Radius Power, we offer comprehensive testing and analysis – including two fully equipped EMC test chambers located in Yorba Linda, CA and Kunshan, China – enabling us to quickly and cost-effectively bring products into compliance. We offer EMI pre-compliance testing to commercial & industrial (FCC, CISPR, EN etc.), military (MIl-STD-461) and aerospace (MIL-STD-461, RTCA-DO160) standards. We have been helping customers achieve compliance with European Union EMC requirements (CE) since their inception. We have thousands of standard and custom EMI/RFI filter designs and in many circumstances, one of these designs can help our customers meet the most demanding product requirements without the need for costly and time consuming efforts.

Pre-compliance testing dramatically improves a device’s chance of passing EMC testing and significantly lowers the risk of failure during the certification process. Failing an EMC test poses a substantial threat to project deadlines and budget – something no company wants to go through.

Our EMC testing engineers are highly trained and experienced in EMI/RFI filter design. They can quickly understand customer’s product, its design and circuitry which enables them to identify potential EMI sources quickly.

Our Client Test Data Program (CTDP) at Yorba Linda offers UL and CSA certification while the ENEC MTL (Manufacturer’s Test Laboratory) offers SEMKO certification, allowing for certification to domestic and international standards. With these labs readily on-site, Astrodyne is able to certify filters to various safety standards including UL 1283, CSA C22.2 No. 8 and IEC/EN 60939-1/2.

Recently our CTDP program was extended to include power supply test and certification capabilities. Power supplies are harmonized to global standards including IEC/EN 60950 (ITE standard), IEC/EN 60601 (medical standard) as well as IECEE SMT (CB Scheme).

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Single Phase EMI Filters

  • UL/CSA/CE
  • Standards to 200A
  • 50/60Hz to 400Hz

Three Phase EMI Filters

  • UL/CSA/CE
  • Standards to 2500A
  • Delta and WYE

IEC Inlet Filters

  • UL/CSA/CE
  • Standards to 20A
  • Multiple Functions

DC EMI Filters

  • UL/CSA/CE
  • Standards to 2500A
  • Voltages to 1200V

Inverter EMI Filters

  • UL/CSA/CE
  • Standards to 2500A
  • Solar / Industrial / Drives

Medical Grade EMI Filters

  • UL/CSA/CE
  • Standards to 2500A
  • Variable Leakage Current

Military EMI Filters

  • MIL-461 / DO-160
  • Standards to 150A
  • 1PH & 3PH Models

Tempest Filters

  • Standards to 225A
  • 1PH & 3PH Models
  • Facility and 100dB Models

Telecom EMI Filters

  • EN60950
  • 48V Systems
  • PCB Mount Models

Custom EMI Filters

  • Any size
  • Any Shape
  • Up to 2500A