What are EMI Filters / EMI Power Line Filters

Electromagnetic interference (EMI) is mainly defined as the unintended harmonic energy that is generated by sharp changes in circuit voltage and current (dv/dt and di/dt). Primary sources include power conversion and logic circuits. This energy can propagate into and within an equipment degrading the integrity of a signal or possibly damaging components, thus affecting the equipment’s overall functionality.

An EMI Power Line Filter is a device that is installed at the power entry point of an equipment to reduce unintended harmonic energy below circuit operational levels, as well as to meet commercial and military international EMI standards. These standards are established and regulated by the FCC, EN/CE and various Government/Military agencies. The main frequencies of concern governing power line conducted emissions are 10KHz to 10MHz for Military environments and 150KHz to 30MHz for commercial/industrial applications. From a design perspective, EMI filters can consist of both passive and active components. However, due to their ability to filter over a broad frequency range, passive designs utilizing inductive and capacitive elements comprise the majority of EMI filter products in the market.

The primary operation of EMI/RFI filters is to provide varying impedances over frequency in opposition to equipment circuit impedances. As EMI power line filters deal primarily with unintended, high frequency harmonic noise their function is reflective. Primarily, the EMI/RFI Filter circuit is designed so that externally or internally generated noise is reflected back to its source. Although it is not technically an EMI application, these are often specified for line harmonic filtering. In this application, the filter’s inductive components must be designed to provide wave shaping of the AC line without saturating. Unlike typical EMI Filter, which primarily utilize common-mode inductive elements that are resistant to line current saturation.

At Premier Filters, we offer an extensive line of standard EMI Power line Filters for all AC and DC applications, including commercial, industrial, military, tempest and facility/SCIF. Our standard offerings are complemented by an almost infinite custom capability with designs to 5K volts and 3k amps. Call 657-226-0091 x702 or email info@premieremc.com to see how Premier Filters can deliver your project on-time and on-schedule.