Utilizing Delta EMI Filters and IEC Power Entry Modules for EMI compliant System Design
Electromagnetic interference (EMI) is an unavoidable component of modern electrical and electronic systems. Switching power supplies, motor drives, and other high-frequency sources generate electrical noise that can propagate through power lines and signal paths. While many power supplies include integrated EMI filtering, additional system components or multiple power supplies can compound EMI.
Without proper mitigation techniques and hardware, this noise can interfere with nearby equipment, degrade system performance, and prevent compliance with regulatory standards such as FCC Part 15 or EN55032.
Our panel-mount and chassis-mount EMI filters from Delta Electronics play a critical role in controlling conducted emissions. Effective EMI filtering prevents these conducted emissions from propagating through connected devices and improves overall operational performance and system reliability. Utilizing our DELTA EMI filters can suppress unwanted high-frequency noise before it can enter (or leave) your device/enclosure.
AC Input EMI Filtering Two Approaches:
There are two primary implementation approaches:
- IEC Power Entry Module (PEM) Integrated
- DELTA EMI Filter (panel-mount or chassis-mount)
Both of which are shown below as Figure 1 and Figure 2.
The key criteria to guide you on which mechanical package to utilize comes down to your system architecture and spatial constraints. If the system does not have a dedicated AC inlet/interface and the space is available within the system, it is recommended to utilize a panel mount, DELTA EMI filter to simplify the installation.
On the other hand, if the AC interface has already been selected or installed and there is a need for attenuation after the fact, this is where the chassis mount DELTA EMI filter can shine. This type of filter can be installed into the system, given that there is sufficient space, to provide the necessary noise attenuation to achieve the desired performance goal.
Understanding Attenuation (Insertion Loss)
Below is an example of an attenuation table. An attenuation table essentially shows you the amount of signal reduction (measured in dB) that the filter provides across a range of frequencies. It can be labeled as the “insertion loss” or how much noise is reduced at specific frequencies. Understanding how to interpret the attenuation table is important in selecting a suitable filter to provide you with the noise suppression to meet your desired performance goal.
Figure 3: Attenuation Table/Graph
When viewing an attenuation table/graph, you will commonly see two curves. They are common mode and differential mode. Understanding these characteristics is essential when selecting a filter for a given application.
Common mode noise appears equally on both conductors relative to ground and is typically caused by parasitic capacitance returning through chassis or grounding paths.
Differential mode noise appears between conductors with opposing currents and is commonly generated by switching circuits, load transients, and rectification.
Medical vs. ITE EMI Filters
The next logical separation is with respect to the application suitability. We are specifically talking about AC line filters that are suitable for medical or ITE applications. The easiest way to identify a DELTA EMI filter that is suitable for a medical application is to look for to following:
- Leakage current: Many filters that are suitable for medical applications will boast very low leakage currents (< 100–300 μA).
- Fusing on both line and neutral: Provides additional safety protection.
- System-level certification considerations: Many medical filters are designed to support IEC 60601-1 systems. However, they are not specifically certified to this standard as they are not standalone components.
Certification applies to the end equipment and not the filter alone. This is one of the main reasons why a filter that is suitable for a medical application may not carry the agency certification.
Selection of AC Current Ratings for Chassis Mount or PEM EMI Filters
Proper selection of the AC input current rating is critical for both performance and safety compliance.
Always verify the certified current rating, not just the nominal rating. For example, a filter may be rated for 10 A at a given input voltage but certified for a lower current depending on agency requirements. This distinction is important during compliance evaluation for standards such as UL 62368-1 or UL 60601-1.
For power entry modules, the IEC 320 inlet type changes for higher current ratings. For example, systems requiring 20 A input current typically require an IEC 320-C19 connector, such as the Delta model 20GENG3E-R, or the use of a chassis-mount filter.
Mechanical/Mounting Interfaces:
When selecting an EMI filter, one of the primary considerations is the mechanical and mounting interface, as this directly impacts how the filter integrates into the system.
The TRC Electronics portfolio for Delta EMI filters are typically offered in two configurations:
Both are designed for direct integration into equipment enclosures where mechanical reliability and ease of installation are critical. These filters commonly include mounting flanges or threaded studs to provide a secure attachment to the panel or chassis. Standardized hole patterns and flange designs are often used to simplify installation and ensure compatibility with the overall system layout.
There are several ways to interface with the different DELTA EMI filters that we offer here at TRC Electronics. Integrated solder lugs and FASTON quick connect tabs are our most common interface offering. Some models we carry also support flying leads and nut/bolt connections. The wide variety of available connection interfaces adds to the ease of installation and ensures strong connections within the system to provide consistent EMI suppression performance.
Summary
Electromagnetic interference (EMI) is a common challenge in systems utilizing switching power supplies, motor drives, and other high-frequency sources. While internal filtering is often present, additional EMI filters are frequently required to control conducted emissions and meet regulatory standards such as FCC Part 15 and EN55032.
Delta EMI filters are available as panel-mount power entry modules or chassis-mount filters, allowing flexibility based on system architecture, space constraints, and integration requirements. Proper selection requires understanding attenuation performance, common mode versus differential mode noise, and application-specific needs such as low leakage current for medical systems.
EMI filtering should be accounted for at the start of the design. Reserving space for an EMI filter early prevents layout constraints and rework later, where retrofitting a filter can be difficult and often compromises performance and compliance.