EMI Filters: Types, solutions and applications

GD Rectifiers partners with Enerdoor to provide state-of-the-art EMI filters designed for every industry and application, including medical equipment, VFDs, renewable energy, recharging stations and automated machinery


lectromagnetic interference (EMI), or radio frequency interference (RFI), is a type of electric or electronic emission that can degrade, impair, or prevent electrical circuit performance. Today, most electronics contain an EMI filter, either as a separate device or embedded in circuit boards. GD Rectifiers works with Enerdoor to provide customers with advanced EMI filters offering cost-effective motor analysis solutions to reduce costs and minimise motor failure. The electromagnetic interference can be a one-time event, random, sporadic, or continuous. The general classification of interference is typically the following: conducted and radiated interference or common mode and differential mode interference.

Types of interference

Conducted and radiated interference 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 energising electric conductors.

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.

Common mode and differential mode interference

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).

Differential mode interference is an undesirable signal measured between two independent conductors of the same electrical circuit (see figure B).

Interference Classifications Conducted interference due to low frequency phenomena

Mains 50/60Hz harmonics and sub-harmonics, signaling systems, voltage variations, interruptions and dips, voltage unbalances, mains 50/60Hz frequency variations, low frequency induced voltage and DC components in AC.

Conducted interference due to high frequency phenomena

Induced voltage or current (continuous or modulated waves), voltage transients (bursts) and oscillatory transients (single or repetitive). Radiated interference due to low frequency phenomena

Magnetic fields (transients or continuous) and electric fields.

Radiated interference due to high frequency phenomena

Magnetic fields, electric fields and electromagnetic fields (transients, continuous or modulated wave).

Benefits of using EMI Filters: EMI filters are used to suppress interference generated by a device or by other equipment, and to protect a device from electromagnetic interference signals present in the environment. EMI filters offer a wide range of benefits including: protects PLCs, sensors, encoders, and PCs from failing, increases life expectancy of sensitive components, increases reliability and reduces production downtime, prevents EMI disturbances in other buildings and machines and ensures compliance with various international standards including CE marking.


EMI filters are widely used in applications such as: machine tools, packaging equipment, automated machinery, renewable energy, filtration systems, medical equipment, VFDs, servo drives, conveyors, printing machines, power supplies, HVAC systems, recharging stations, multiple drive installations, laser equipment, CNC machines, and various other applications.

CE Certification Pre-Compliance Testing

CE Certification is required when shipping machines overseas and today on average 50 per cent of products fail first time EMC testing. EMC issues within an EMC lab can cost customers tens of thousands of pounds in re-design, re-manufacturing and re-testing costs, adding unnecessary delays to your time to market schedule.

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. Enerdoor’s EMI filters are also CE marked, so that they can be sold in Europe, ensuring manufacturers take responsibility for the compliance of a product with all applicable European health, safety, performance and environmental requirements. The global equivalents to the CE mark are: FCC in the United States, CCC in China, VCCI in Japan, RCM in Australia & New Zealand, and KCC in South Korea.

EMI Filter Solutions in the UK GD Rectifiers is Enerdoor’s official UK distributor and offers their extensive range of EMI/RFI filter solutions to reduce electromagnetic interference. Offering a large variance of electrical and mechanical characteristics, Enerdoor filters cover standard nominal voltage from 0 to 750Vac with the following nominal currents: single-phase EMI/RFI filters from 1 to 100A, three-phase EMI/ RFI filters from 3 to 3000A and three-phase plus neutral filters from 3 to 3000A. Enerdoor also offers a unique EMI parallel filter solution, designed for the specific frequency range of

36 July/August 2020 Components in Electronics

10KHz – 6MHz where there is severe risk of interference and disturbance.

With decades of experience in the design and manufacture of EMI filters for the commercial, industrial, medical and military markets, GD Rectifiers works with Enerdoor to help companies succeed and operate within pertinent electronic and energy standards. Enerdoor is a manufacturer and global leader in EMC and CE Certification testing which enables them to uniquely support customers efficiently and cost effectively. As one of the top-ranked CE labs in the world, Enerdoor offers a wide range of testing methods and standard compliance. The flat rate, on-site testing is unique in the industry and improves a products chances of passing EMC and CE Certification testing, lowering the risk of failure.

Enerdoor’s EMI Filters

Enerdoor provides decades of electromagnetic compatibility and motor protection experience with a track record of solving compatibility issues for companies around the world. Offering an advanced support system of global laboratories and affiliated organisations, helps expedite the process of meeting Certification requirements. Enerdoor testing capabilities include: Enerdoor CE Certification and Consulting, testing for the EMC Directive 2014/30/EU, FCC tests, risk assessment and machinery Directive review, low voltage testing to meet the 2014/35/EU Directive, non-ionizing radiation measurement for the 2013/35/EU Directive, electric and magnetic field measurements around the machine, power analysis and consulting to reduce energy costs and motor analysis and cost-effective solutions to minimise motor failure.

GD Rectifiers offers competitive pricing, expert technical support and fast delivery on all Enerdoor products. As Enerdoor’s exclusive UK distributor, GD Rectifiers works closely with customers on their product specification, budget and delivery requirements and are able to organise call-off and scheduled orders to ensure stock is always on the shelves at their factory in Burgess Hill, West Sussex.

For further information on Enerdoor’s EMI Filters or to discuss your requirements, please call our team today on: 01444 243 452 or email:

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