This blog post presents the most common electromagnetic compatibility (EMC) issues found in electrical equipment.
What is electromagnetic compatibility?
Electromagnetic compatibility, or EMC for short, describes the condition that no component on a product creates electric or magnetic effects that trigger any other electrical part to fail to operate correctly. All electrical equipment should function reliably in a hostile electromagnetic environment and shouldn’t degrade the same environment to the extent of causing unpredictable operation in other equipment. Due to that, electromagnetic compatibility splits neatly into two areas, labelled “immunity” and “emissions”. Each of these areas is subject to legislation from one source or another.
As a result of the latter, EMC has become a significant consideration on any project involving the design, assembly, manufacture and installation of electrical and electronic equipment (EEE) and systems. Thus, as a product designer/manufacturer, your job is to ensure that your product operates within the acceptable limits of interference immunity and suppression. Otherwise, your product’s poor EMC performance can cause extremely high costs (e.g. product redesign, retesting for compliance and damaged reputation).
Electromagnetic Compatibility (EMC) Legislation in Europe
All electrical equipment and systems placed on the EU market must comply with the Electromagnetic Compatibility (EMC) Directive 2014/30/EU. The Directive came into force in April 2016 and is aligned to the New Legislative Framework. It ensures that all EEE comply with the allowed levels of electromagnetic compatibility. Compliance with the EMC Directive is necessary for obtaining CE marking.
The Electromagnetic Compatibility Directive sets forth mandatory essential requirements that all products within its scope must fulfil. These requirements do not specify technical specifications but define the results to be achieved. Also, they’re legally binding for all electrical equipment falling within the Directive scope.
What are the most common electromagnetic compatibility (EMC) issues found in electrical equipment?
Find below some of the most common electromagnetic compatibility issues in electrical equipment.
#1. High-frequency emissions
- Conducted emissions – Limiting conducted EMI is probably the most common electromagnetic compatibility issue of electrical equipment not explicitly designed to fulfil the requirements of the applicable standards for compliance with the EMC directive. You can drastically reduce the noises by paying attention to reduce loops area and wires length, by carefully evaluating the system layout, slowing down the edges of the switching waveforms and avoiding magnetic and capacitive coupling.
- Radiated emissions – Radiated noises can result from correlated physical phenomena. Open-site test areas are generally affected by a level of base noises well above the allowed emission limits in a large part of the frequency spectrum. This, in turn, impedes the realization of measurement tests. An excellent solution to this problem is to perform compliance tests in anechoic chambers. Furthermore, another radiated emission issue can occur due to improper grounding or displacement of equipment and cables. The best tactic to solving this issue is by considering the radiation aspects during the design phase.
- Disturbance power – The power radiated from the cables of a product not always falls within the allowed MHz range. A solution is to put ferrite cores at the cable’s starting end to absorb the equipment’s noises before being transmitted through the cable.
- Discontinuous disturbance – Discontinuous disturbances are caused by switching operations of electrically controlled appliances. The main issues here are associated with the measurement technique, which demands statistical investigation and long measurement times.
The main EMI phenomena are generated by electronic circuits containing high-power switches (e.g. semiconductors and relays) and digital gates. Reverse recovery of power diodes and forced commutation of high-power switches are some of the most common causes of EMI.
#2. Immunity issues
These issues relate to the capability of electrical equipment to operate properly in the presence of electromagnetic stresses. For instance, you can experience problems with powering frequency magnetic fields or assessing immunity against supply voltage variations. Depending on the type of electrical product you have, you may need to perform various types of immunity tests (e.g. electrostatic discharge test and surge immunity test) to prove compliance with the relevant standards of the EMC directive.
#3. Harmonic pollution
Nowadays, more and more harmonic loads are connected to the grid. The high distortion of the current absorbed by these loads leads to a considerable line voltage distortion. You can solve such EMC issues with both passive and active solutions. Passive solutions, such as an inductor or L-C cell placed in-between the line terminals and the load, are usually applied in the lower power range. Active solutions include power switching stages and allow high power factor operation, as well as possible insulation with high-frequency transformers.
#4. Flicker and line disturbances
Equipment with fans, pumps and compressors tend to absorb considerable overcurrents at start up or during line and load transients. Thus, causing voltage instabilities and flicker due to the voltage supply drop across the power supply impedance. To avoid such electromagnetic compatibility issues, you must select proper starting capacitors of induction motors and apply voltage-limiting devices to reduce transient overcurrents.
How can Clever Compliance assist you?
Clever Compliance is an innovative Swedish company known for developing ground-breaking compliance management solutions, such as their product compliance management system and supplier compliance software with SCIP integration.
Many of the above-stated issues can be avoided by having a product design compliant with all relevant EMC standards and requirements. However, managing a compliance project for a new product is not an easy task, and this is where Clever Compliance comes. Our compliance management system can help you:
- streamline compliance work (use digital tools to identify relevant legislation and standards),
- improve team collaboration and coordination,
- monitor the regulatory framework for updates and changes to standards,
- create custom roadmaps to keep track of the compliance status of any project,
- create compliance documentation, and much more.
To learn more, get in touch with us at [email protected].
Source:
- Wilson, P., “The Circuit Designer’s Companion”, Elsevier Ltd., 2018, pp. 365-400
- Rossetto, L. et al., “Electromagnetic Compatibility Issues in Industrial Equipment”, EEE Industry Applications Magazine, November/December 1999.
- https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A32014L0030
- http://ec.europa.eu/growth/sectors/electrical-engineering/emc-directive_en
