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Functional Safety: Understanding the New EMF and EMC RequirementsChris Zombolas CE marking requirements now include compliance with electromagnetic field and electromagnetic compatibility standards. Manufacturers must ensure that products already on the market comply.
To legally market electrical and electronic products in the European Union (EU), the CE mark must be applied—but only after establishing compliance with all applicable directives. It is well known that the Electromagnetic Compatibility (EMC) Directive (89/336/EC) and the Low Voltage Directive (LVD; 73/23/EC) apply to most electrical and electronic products and that compliance is established by testing to the applicable harmonized standards listed in the Official Journal of the European Union. This article explains some major new compliance requirements for the safety of electrical and electronic products in relation to the effects of electromagnetic fields (EMF) and EMC on the functional safety of equipment. New EMF Requirements EU Recommendation (1999/519/EC) was introduced in 1999. It provides basic restrictions to protect the general public from EMF exposure. The EMF at Work Directive (2004/40/EC) protects workers from the risks arising from the exposure to EMF in the workplace. It is not a directive required for CE marking; rather it is part of the EU Occupational Health and Safety regulations. This directive does affect manufacturers indirectly, however; employers and others will not purchase equipment that does not allow them to meet their legal obligation to provide a safe workplace. The Radio and Telecommunications Terminal Equipment (R&TTE) Directive (1999/5/EC) mandates essential requirements for the protection of the health and safety of a user or any other person. The LVD now requires that users of household electrical equipment be protected from the possible harmful effects of EMF that may arise from radio-frequency (RF) transmitters or from the magnetic fields associated with high currents and ferromagnetic applications. The Official Journal’s list of harmonized standards for the LVD and R&TTE directives now includes various EMF standards that set limits for human exposure to EMF. The following standards can be used to demonstrate compliance with the new EMF requirements: • EN 50360:2001—Product Standard to Demonstrate the Compliance of Mobile Phones with the Basic Restrictions Related to Human Exposure to Electromagnetic Fields (300 MHz–3 GHz).
EN 50360:2001. This harmonized standard has been in force under the R&TTE Directive. It applies to mobile phones and similar devices used near the ear and operating in the frequency range of 300 MHz–3 GHz. It can be used to demonstrate compliance with the essential safety requirements (relevant to human exposure) of the R&TTE Directive. The basic restrictions on EMF exposure are met by measuring the specific absorption rate (SAR) in accordance with the methodology prescribed in the companion basic standard, EN 50361. This standard is not applicable for devices that are not used near the ear. IEC 62209-1:2005 will replace this standard in the near future. Innovative products tend to employ new RF transmitter technologies, which often means a lag in the development of appropriate standards and measurement techniques. For example, there are still no published standards for the SAR measurement methods to be used on 5.2–5.8 GHz cordless phones and wireless local-area network (WLAN) devices used in close proximity to the human body. IEC 66209-2 is under development and is expected to partly fill this gap when published. EN 50366:2003. This standard is listed under the LVD but not under the R&TTE Directive. It sets limits for EMF generated by household appliances and similar devices over the frequency range of 10 Hz–400 kHz. It applies to all mains-powered equipment under the scope of the EN 60335, Amendment 1:2004, range of standards. The scope of EN 50366 also includes “appliances not intended for normal household use, but which nevertheless may be accessible to the general public, such as appliances intended for use by laymen in shops, in light industry, and on farms.” EN 50366 has a wide scope and appears to cover virtually all electrical equipment that may be used in residential, commercial, light industry, or farm environments. Compliance may be established by one of the following methods: • Declaration of conformity (DoC) for benign products. EN 50366 specifies EMF limits and test and measurement methodologies.
EN 50371:2002. This standard is listed under both the LVD and the R&TTE Directive. It sets limits for the exposure of the general public to RF EMF from low-power electrical and electronic products incorporating RF transmitters with an average power not exceeding 20 mW and 20 W peak over the range of 10 MHz–300 GHz. The use of low-power RF transmitters in equipment is rapidly increasing in homes, businesses, factories, and in many other environments. This harmonized standard captures most household and similar devices that employ wireless applications. EN 50371 now appears in the Official Journal of the European Union for both the LVD and the R&TTE Directive. It applies to all products under the scope of those directives. Compliance with this standard demonstrates that the basic restrictions for human exposure to EMF will not be exceeded. Compliance can be demonstrated by preparing an assessment report that shows that the transmitted RF power does not exceed 20 mW average and 20 W peak. The report should contain all the information needed for performing repeatable assessments, tests, calculations, and measurements, giving results within the required calibration and uncertainty limits. EN 50364:2001. This standard appears under the LVD and under the R&TTE Directive. It sets limits for exposure of the general public to EMF from RFID and EAS products in the range of 0 Hz–10 GHz. The products covered include walk-through security systems, electronic tags, smart cards, and antitheft devices, to name a few. EN 50364 has two EMF exposure categories: general-public exposure and occupational exposure. The general-public exposure limits are much lower than the occupational exposure limits. Two methods can be used to determine compliance.
Exposure can be measured by modeling or by direct measurement in accordance with the procedures given by the companion basic standard EN 50357:2001. Measurement methodologies vary greatly depending on the nature of the emitted EMF. Methodologies include simple field measurements, contact currents, limb currents, and localized SAR. EN 50385:2002. This standard is listed only under the R&TTE Directive. The scope covers base stations for mobile phones and other similar products. It also appears to cover base stations for WLAN, DECT, cordless phones, and similar products. Compliance with the basic restrictions of the standard is demonstrated by establishing the boundaries or distances at which the EMF levels do not exceed the general-public limits. The compliance boundaries are established by the methodologies given by the companion basic standard EN 50383:2002. The manufacturer must ensure that the safe boundaries are not compromised. The separation distance from the device must be maintained to a minimum distance such that the EMF levels are below the general-public limits.
Many electrical appliances now employ electronically controlled switching, which creates a potential for electromagnetic interference that may cause inadvertent operation, thereby presenting a functional safety hazard to the user. EMC is now included in some product safety standards. It appears on the LVD list of harmonized standards, and all products on the market after October 1, 2006, must comply. Amendment 1:2004 to EN 60335-1:2002 (Household and Similar Electrical Appliances—Safety—Part 1: General) introduced the EMC functional safety requirements for all products having electronic protective switches or electronic circuits that operate an off switch or a standby switch. Electrical appliances are tested for immunity to rather high levels of electromagnetic disturbances in accordance with the same EN 61000-4-xx basic immunity standards that are used by various EMC standards under the scope of the EMC Directive and R&TTE Directive. The new EMC requirements under EN 60335 are the following: • EN 61000-4-2—Electrostatic discharge (ESD) to levels of 8 or 15 kV. Three criteria must be met to demonstrate compliance: • The appliance does not undergo a dangerous malfunction.
These Level 4 immunity requirements under EN 60335 are generally much tougher than those under the EMC Directive. For the EMC Directive, the Level 2 immunity requirements generally apply for the same products that are covered under EN 55014-2. The immunity tests under EN 60335 must be applied during the assessment of possible fault conditions, such as when a protective circuit is required to operate or after each fault condition is simulated. For some products, this Level 4 requirement will mean much longer test times. It requires a very detailed and thorough test regimen to ensure that all applicable operating modes and failure conditions are adequately tested. Designing for compliance with Level 4 immunity requirements presents challenges for manufacturers, whereas carrying out the new EMC functional safety tests presents more challenges for test houses. Preparing a combined test plan that covers both the EMC Directive and the LVD can maximize test house efficiency and reduce testing costs. Once each Level 2 EMC immunity test under EN 55014-2 is satisfied, the product can be reconfigured to test for functional safety. The tests can then be repeated with a Level 4 disturbance in accordance with EN 60335. Conclusion CE marking requirements now include compliance with EMF and EMC functional safety standards. Manufacturers of affected products should familiarize themselves with the new requirements and identify all applicable harmonized standards. Manufacturers must ensure that products already on the market comply with the new requirements. Chris Zombolas is technical director of the EMC Technologies group and is based in Melbourne, Australia. He can be reached at chris@emctech.com.au.
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