complexities of EMC testing EMC & Thermal Management
Understanding the By Pete Dorey, principal consultant at TÜV SÜD E
lectromagnetic compatibility (EMC) testing measures the ability of equipment or systems to function satisfactorily in their electromagnetic environment without introducing intolerable electromagnetic disturbance to anything in that environment. EMC compliance is a mandatory requirement in most markets, including Europe, the US, China, Korea, Australia and New Zealand. In the EU, the majority of electrical products must comply with the EMC Directive 2014/30/ EU, as well as other relevant Directives, before they can carry the CE marking. Following Brexit, in the UK the Electromagnetic Compatibility Regulations 2016 continue to be applicable from January 2021, and products must comply with this before they can carry the UKCA marking (UK Conformity Assessed). There is a transitional measure that allows CE marking to continue to be used in Great Britain for one year. Arrangements
for Northern Island differ and require the continued use of CE marking. This means that for the foreseeable future, the requirements of the UK Regulations will remain the same as those of the EU’s EMC Directive. The main differences for UKCA marking are that the required standards are known as “designated standards” rather than “harmonised standards” and “Conformity Assessment Bodies” replace “Notified Bodies” in the UK. EMC is an issue that many designers and manufacturers find complex and confusing, but that does not mean that they can ignore their legal obligation to ensure their products meet requirements. Neither should those manufacturers integrating components into their final product plead ignorance, making the assumption that their supplier is doing the right thing.
The standards set strict limits for emissions, which is the amount of electrical interference that a device produces and limits on the required immunity of the product to its intended electromagnetic environment. Equipment must be designed and manufactured so that the electromagnetic disturbance it creates is not excessive, and so that it has a reasonable level of immunity to electromagnetic disturbances. While a single item of equipment might meet these limits, there is no guarantee if you combine multiple numbers of them or additional components, that for example, the overall emission levels will still be satisfactory.
Not only does EMC testing ensure that products meet regulatory requirements, it reduces the risk of costly non-compliance, which could require product recalls, or cause significant time-to-market delays for new products. Third-party EMC tests and conformity assessments help to ensure that a product maintains its desirable features when exposed to adverse conditions (immunity test) and does not cause undue interference (emission test).
12 June 2021 Components in Electronics
This can help to strengthen a brand’s competitive position in the market due to improved product performance and reliability by reducing the chances of failures in use. The two key drivers of brand loyalty and product quality can therefore both be beneficially influenced by such tests, helping to ensure that the product maintains its desirable features when exposed to adverse conditions will support brand loyalty.
For immunity testing there are three performance criteria A, B and C that are specified in the EMC standards and each immunity test has one criteria specified. Criteria A requires the product to continue operating as normal at all times and applies to tests for continuous EMC phenomena (like immunity to adjacent mobile phones). Criteria B allows some degradation during the test condition and applies to tests for transient immunity (infrequent events, such as electrostatic discharge due to someone touching the equipment). Criteria C allows temporary loss of function and applies to severe transient immunity which is very infrequent, such as a power surge or supply voltage interruptions. Permanent loss of function will be a failure.
Manufacturers can minimise the costs and time associated with EMC testing by proper preparation for test:. A test laboratory sees many thousands of products each year – they will not be familiar with your product, so you must brief them fully. A successful testing programme is the result of you disclosing as
much information to your chosen EMC test laboratory about the equipment under test (EUT) as early as possible in the project cycle., with a special focus on: • Block diagram of the test configuration and any support equipment to exercise or monitor the EUT
• Mode of operation for emission to maximise potential interference and highest internal operating frequencies
• Mode of operation for immunity to exercise critical functions and method of monitoring to determine if function is upset or degraded • Power supply requirements • List of signal interface ports, type and cable lengths
• Grounding arrangement
This information will help the laboratory to develop a realistic test plan, enabling you to more accurately anticipate time and cost for test.
Consideration of EMC at earliest stage in the design process will help manufacturers to minimise test failures and the time and cost for reworking their design and retesting. A product lifecycle review will also highlight any design measures required to maintain a product’s compliance. This will help manufacturers increase the return-on- investment that they get from their EMC testing, help to ensure that the EMC integrity of products lasts a lifetime and enhance a brand’s reputation for product reliability.
tuvsud.com/uk
www.cieonline.co.uk
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