Electrical appliances

EMC – Electromagnetic compatibility

The purpose of electromagnetic compatibility (EMC) is to ensure that electrical equipment do not cause disturbances that would affect other equipment and are immune to disturbances caused by them. Electromagnetic compatibility is regulated by the Electrical Safety Act and the EMC Directive.

What is an EMC disturbance?

Disturbances in electrical product or fixed installation include all electromagnetic phenomena not intended for practical use. All electrical products and fixed installations affect each other when they are in close proximity or connected. Disturbances spread to other products and fixed installations either through cables or via radiation. For example, lines in a television picture, static on the radio or computer malfunctions are often due to disturbances caused by other electrical products and fixed installations.

Scope

The EMC Directive applies to all electrical product that may cause electromagnetic disturbances or whose functioning may be affected by electromagnetic disturbances. The EMC Directive does not apply to:

• EMC passive appliances, i.e. appliances which are inherently benign in terms of electromagnetic compatibility
• Radio equipment
• Aeronautical products
• Radio equipment used by radio amateurs
• Custom-built evaluation kits designed for professionals to be used at research and development facilities

Examples of EMC passive electrical appliances:

• Appliances containing only resistive loads without electronics (simple heaters without temperature control, thermostat or fan)
• Batteries and accumulators (without active electronic circuits)
• Passive speakers
• Flashlights without active electronic circuits  
• High voltage inductors and transformers
• Induction motors without electronic circuits Quartz watches (without additional functions such as a radio receiver) 
• Home and building switches which do not contain any active electronic components 
• Connectors, plugs, cable terminals, etc.

If the EMC requirements of electrical equipment are wholly or partly laid down in more special legislation, the EMC Directive shall not apply to that equipment in that respect. For example, the EMC Directive does not apply at all to:

• Radio equipment (the Radio Equipment Directive refers to the essential requirements of the EMC Directive)
• Medical devices
• Vehicles and their equipment
• Vehicles with 2–3 wheels
• Marine equipment
• Agricultural and forestry tractors

The EMC Directive partially applies to measuring instruments and non-automatic weighing instruments. In these cases, the emission requirements are laid down in the EMC Directive, and the immunity requirements in special legislation. There are stricter immunity requirements for these product groups, because their measuring result determines the price of the product or substance to be measured. 

Impact of operating environment on EMC requirements

The legislation, the Electrical Safety Act and the EMC Directive, include only essential requirements concerning electromagnetic compatibility and labelling requirements for electrical products. The standards lay down the limit values for immunity and emissions requirements. The limit values take into account the intended operating environment of the product, i.e. whether its intended use is in a residential area or in industry, for example. In an industrial environment, the limit values for emissions are somewhat higher than in a residential area, but correspondingly, the appliance must endure more disturbances. 

If the product is not intended for use in a residential area, a clear indication of such restriction of use must be included with the product and also on the packaging, where appropriate. The consumer must know about the restriction before making the purchase decision.

The descriptions used in harmonised standards (for example “this is a class  A product”) are not suitable without further explanation, as they are not understood by the general public.You could mark a restriction as follows:

• This product must not be used in residential areas.
• This product may cause interference if used in residential areas. Use in the residential area must be avoided unless the user takes special measures to reduce electromagnetic emissions to prevent interference.

Standardisation and testing

EMC standards are divided into generic standards and product and product family standards. The generic EMC standards are related to a specific operating environment. They define several essential EMC requirements and test procedures for products intended for use in a specific environment. Generic EMC standards can be used when there is no specific product or product family standard for the product.

The European Commission maintains a list of harmonised standards under the EMC Directive. If the electrical product has been tested in accordance with all the relevant harmonised standards, it has a presumption of conformity, i.e. it is presumed to comply with the essential requirements of the EMC Directive.

EMC testing of electrical products includes both emission and immunity tests. Both emission and immunity tests include measurements for both conductive and radiated disturbances. The tests are mostly performed by an external testing laboratory, as only few companies in Finland have their own EMC testing laboratory.

In general, the following EMC tests must be carried out on electrical products:

• emissions
• Radiated disturbances (product, product family or generic standard)
• Conducted disturbances (product, product family or generic standard)
• Harmonic currents (EN 61000-3-2 or EN 61000-3-12)
• Voltage fluctuations and flickers (EN 61000-3-3 or EN 61000-3-11)
• Immunity (product, product family or generic standard)

The European Electrotechnical Committee for Standardization (CENELEC) has published a guide to EMC testing of electrical products (CENELEC Guide 25: Guide on the use of standards for the implementation of the EMC Directive to apparatus). For more information about standards, contact the National Electrotechnical Standardisation Organisation (SESKO). You can buy a copy of the standards from the Finnish Standards Association (SFS) webstore.

Issues to consider in EMC assessment

The EMC assessment must consider not only the operating environment, but all normal operating methods of the electrical product. For example, if the product can be used and charged at the same time, the product must be tested according to the “worst case scenario”, i.e. when the appliance is charged and used at the same time.

The EMC requirements apply to the whole set of equipment that is commercially available. The entity can be a combination of several equipment. The combination of two or more CE marked equipment does not automatically produce a compliant entity. Instead, the conformity of the combination of equipment must always be assessed separately.

In cases where the electrical product might be included in different assemblies, the electromagnetic compatibility assessment ensures that the product meets the requirements in all possible assemblies. In this case too, the “worst case scenario”, i.e. the assembly with all the accessories/features, is tested. The manufacturer is responsible for identifying possible assemblies and choosing the worst-case scenario.

Conformity assessment

As the conformity assessment procedure for the electrical products, the manufacturer can use either the internal production control set out in Annex II of the EMC Directive or the EU-type examination that is followed by the procedure concerning conformity to type based on internal production control set out in Annex III. In the procedure set out in Annex III, the notified body participates in the conformity assessment of the electrical product. The use of notified bodies is therefore not obligatory. The documents and test reports in accordance with the conformity assessment procedure are attached to the technical documentation. Further information on conformity assessment procedures can be found in the Annexes to the EMC Directive.

Although the standards set limit values only for certain frequency bands, the electrical product must not cause undue interferences at any frequency. Risk assessment is essential in assessing a product’s conformity. This risk assessment must be added in the technical documentation. 

Changes to the electrical product’s design or features, along with changes to harmonised standards or technical specifications based on which the conformity of the product is assessed, must be considered in the EMC assessment. If necessary, the conformity of the electrical product must be reassessed.

Installation, use and maintenance instructions

The electrical product must be accompanied by the necessary instructions for its safe and appropriate use. The electrical product must also be accompanied by the necessary information for its installation, assembly, operation and maintenance to comply with the essential requirements of the EMC Directive. Examples of cases where it is necessary to provide more detailed information:

• The grounding of the product involves special aspects
• Special types of cables are required to connect the product (such as protected, double protection)
• The product is not intended for use in a residential area (information must also be provided on the packaging if necessary)

Where no detailed information is provided with the product, it is assumed that users can install the product without special consideration for EMC factors, and that the product still complies with the essential requirements of the EMC Directive.

Read more about EMC:

Electromagnetic compatibility – EMC on the Tukes website 

I Know My Product webinar: Electromagnetic compatibility (EMC)

EMC Directive (PDF)

Application guide for the EU EMC Directive, in English (PDF)

Harmonised standards of the EMC Directive

SESKO’s presentation on the EMC standards

CENELEC Guide 25