I make LED lights, but I buy needed transformers from the market. Is it enough that I only EMC test the luminaire?

The transformer is an integral part when assessing the electromagnetic compatibility of a LED light. The EMC assessment must therefore be performed for the whole unit on sale, i.e. the luminaire + transformer unit. Of course, the manufacturer of the transformer has already made an EMC assessment for the product. However, a resistive load has been used in the EMC tests, as the transformer manufacturer does not know where it will be used. However, the disturbances caused by transformers depend very much on the load used, and as load, the LED lights are anything but resistive.

I use a charger from another manufacturer in my product. However, the manufacturer of the charger has stopped producing the charger in question, so I have purchased another charger for my product. Does the product need to be EMC tested again, as the charger is already CE marked?

The charger is an integral part when assessing the electromagnetic compatibility of a product. The EMC assessment should always be performed for the entire device combination on sale. Changes in the product must be considered in the conformity assessment. A combination of two CE marked devices does not automatically produce a compliant assembly. The change of the charger is significant enough that the EMC assessment of the product must be performed again.

Electromagnetic compatibility - EMC

The emissions from electrical devices and equipment and their immunity to disturbances must comply with the requirements. All electrical devices and equipment affect each other when they are in close proximity or connected. The purpose of electromagnetic compatibility (EMC) is to ensure that electrical devices or equipment do not create disturbances that would affect other devices or equipment and are immune to disturbances caused by them.

The manufacturer of the electrical device or equipment is responsible for ensuring that the device or equipment is compliant with the requirements of the EMC Directive. Electromagnetic compatibility is regulated by the Electrical Safety Act and the EMC Directive.

What is an EMC disturbance?

Disturbances in electrical devices or equipment include all electromagnetic phenomena not intended for practical use. Disturbances spread from equipment or a device to other equipment or devices 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 devices or equipment.

Scope of application

The EMC Directive applies to all electrical devices or equipment that may cause electromagnetic disturbances or whose functioning may be affected by electromagnetic disturbances.

The EMC Directive does not apply to

radio equipment
aeronautical products
radio equipment used by radio amateurs
Custom-built evaluation kits destined for professionals to be used at research and development facilities
installations or equipment which are inherently benign in terms of electromagnetic compatibility.

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 devices or equipment are provided for in another legislation in whole or in part, the EMC Directive shall not apply 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 includes 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.

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.

How to ensure the conformity of electrical devices

Check the essential requirements concerning electromagnetic compatibility specified in the EMC Directive. The manufacturer can demonstrate that the electrical device complies with the essential requirements by testing the electrical device in accordance with harmonised standards.

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 SFS Finnish Standards webstore.

The manufacturer must check and test that the electrical device fulfils the requirements of the EMC Directive in accordance with the conformity assessment procedure included in an annex to the Directive. As the conformity assessment procedure, the manufacturer can use either the internal production control set out in Annex II, 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.

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.

Whether a third party, a Notified Body, needs to be involved in assessing the conformity of an electrical device depends on the conformity assessment procedure used by the manufacturer.

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 manufacturer must draw up technical documentation for the electrical device. In addition to technical documents, the EU Declaration of Conformity must also be prepared.

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.

In addition to the CE marking, the manufacturer must also attach the other markings required by the Directive to the electrical device, such as the traceability requirements. If the device is not intended for use in a residential area, a clear indication of such restriction of use must be included with the device and also on the packaging, where appropriate.

Obligations of the manufacturer, importer and seller

In addition to product requirements, the EMC Directive creates a number of obligations for the manufacturer, importer and seller of the product.

How to ensure the conformity of electrical equipment

The EMC Directive includes different regulations on electrical equipment from those on electrical devices, because electrical equipment cannot move freely within the European Union.

The manufacturer of electrical equipment must design and build the equipment in accordance with good engineering practices so that when maintained and repaired correctly, the electrical equipment is electromagnetically compatible. Electromagnetic compatibility means that the installation fulfils the essential requirements of the EMC Directive concerning electromagnetic compatibility as well as the specific requirements for fixed installations.

The manufacturer of the electrical equipment must document the engineering practices applied and hand the documentation over to the possessor of the electrical equipment.

An electrical device incorporated in a specific fixed installation

If an electrical device is incorporated in a specific fixed installation and is not available for sale otherwise, the manufacturer of the device does not need to carry out a conformity assessment procedure on the device in accordance with the EMC Directive. However, the product may not compromise the EMC characteristics of the fixed installation. The manufacturer does not need to draw up an EU Declaration of Conformity for the device or affix a CE marking.

In the documentation of the electrical device, the manufacturer must

identify the fixed installation in question
indicate the precautions to be taken for the incorporation of the device into the fixed installation in order not to compromise the conformity of that installation
provide the information and markings required by the EMC Directive.

Frequently asked questions

The transformer is an integral part when assessing the electromagnetic compatibility of a LED light. The EMC assessment must therefore be performed for the whole unit on sale, i.e. the luminaire + transformer unit. Of course, the manufacturer of the transformer has already made an EMC assessment for the product. However, a resistive load has been used in the EMC tests, as the transformer manufacturer does not know where it will be used. However, the disturbances caused by transformers depend very much on the load used, and as load, the LED lights are anything but resistive.
The charger is an integral part when assessing the electromagnetic compatibility of a product. The EMC assessment should always be performed for the entire device combination on sale. Changes in the product must be considered in the conformity assessment. A combination of two CE marked devices does not automatically produce a compliant assembly. The change of the charger is significant enough that the EMC assessment of the product must be performed again.