EMI-RFI Filters

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Introduction

Electromagnetic interference (EMI), or radio frequency interference (RFI), is a type of electric or electronic emission that can degrade, impair or prevent electrical circuit performance.

EMI filters are used to suppress interference generated by the device, or by other equipment, and to protect a device from electromagnetic interference signals present in the environment. Most EMI filters consist of components that suppress differential and common mode interference.

To protect and optimize equipment, Enerdoor EMI-RFI filters provide solutions in three product categories: single-phase, three-phase, and three-phase plus neutral filters.

EMC Directive

Electromagnetic Compatibility (EMC) refers to the ability of equipment or systems to operate in an electromagnetic environment without introducing intolerable electromagnetic interference to anything in the environment. EMC includes two important aspects: emission and immunity.
Emission: The phenomenon by which the electromagnetic energy is emitted from a source such as a device, machine or system and shall not emit undesirable electromagnetic interference of a higher level than those allowed by the European EMC Directive 2014/30/EU (See Figure 1).
Immunity (To Interference): The capability of a machine, equipment or system to correctly operate without degrading functional characteristics when affected by electromagnetic interference.

Many countries have established regulations to minimize the radio-frequency interference between electronic equipment including: the CE mark in Europe, FCC in the United States, CCC in China, VCCI in Japan, RCM in Australia & New Zealand, and KCC in South Korea.

The global guideline for electromagnetic interference is the European Directive 2014/30/EU which requires that  manufacturers of industrial machine tools and electric and electronic equipment comply with the electromagnetic compatibility emission and immunity Standards.

Example of typical high frequency disturbance generatedby an automated machine operating without and withfiltering necessary to comply with the European EMC Directive Framework 2014/30/EU limits.

General Classification of Interference

1. Conducted and radiated interference
   1. Conducted interference is caused by the physical contact of undesirable voltage or current signals that enter or exit from a specific device through its own signaling or energizing electric conductors.
   2. Radiated interference is caused without physical contact of conductors. Every electric circuit acts as an aerial and when dipped in an electromagnetic field may induce voltage interference. Every variable current flowing in an electric conductor creates an electromagnetic field in its surrounding environment and similarly each electromagnetic field induces an electric signal in a close conductor.
2. Common mode and differential mode interference
   1. Common mode interference is an undesirable signal measured between all conductors of an electric circuit connected together and a common reference, usually the earth (See Figure A).
   2. Differential mode interference is an undesirable signal measured between two independent conductors of the same electrical circuit (See Figure B).

Problems generated by EMI-RFI interference 

• PLCs, sensors, encoders and PCs failing
• Decreased life of sensitive components
• Production downtime
• Disturbance in other buildings / machines

Interference Classification

1. Conducted interference due to low frequency phenomena
   • Mains 50/60 Hz harmonics and sub-harmonics
   • Signaling systems
   • Voltage variations, interruptions and dips
   • Voltage unbalances
   • Mains 50/60 Hz frequency variations
   • Low frequency induced voltage
   • DC components in AC
2. Conducted interference due to high frequency phenomena
   • Inducted voltage or current (continuous or modulated waves)
   • Voltage transients (bursts)
   • Oscillatory transients (single or repetitive)
3. Radiated interference due to low frequency phenomena
   • Magnetic fields (transients or continuous
   • Electric fields
4. Radiated interference due to high frequency phenomena
   • Magnetic fields
   • Electric fields
   • Electromagnetic fields (transients, continuous or modulated wave)

High Frequency Solution

To protect and optimize equipment performance, Enerdoor offers one of the largest ranges of solutions to reduce electromagnetic / radio-frequency interference. Offering a
large variance of electrical and mechanical characteristics, Enerdoor EMI/RFI filters cover standard nominal voltage from 0 to 750 Vac with the following nominal currents:
Single-phase EMI/RFI filters: from 1 to 100A
Three-phase EMI/RFI filters: from 3 to 3000A
Three-phase plus neutral EMI-RFI filters: from 3 to 3000A
Parallel EMI/RFI filters: In addition to the above EMI/RFI filter lines, Enerdoor offers a unique parallel filter solution. This line is designed for the specific frequency range of 50 kHz – 10 MHz where there is severe risk of interference and disturbance.