Clearing up the confusion

GREGG KERVILL questions the fundamental need to apply the CE Marking to motors and industrial controllers, and examines both the policy and the technical issues involved

CE Marking is a paradox. It is both clear cut, and confused. It is, on the one had reassuring, but at the same time it cannot be relied upon.

Consider the following: if a product has functionality `in its own right’ then it is relevant to apply the CE Marking. Also, `Safety Components’ covered by the UK Supply of Machinery (Safety Amendment) Regulations 1994 may bear the CE Marking.

Both statements seem clear and unambiguous. Now consider, through, that while component manufacturers throughout the rest of the EU seem to apply the CE Marking to their components, in the UK applying the CE Marking may be a technical breach of the UK Trades Descriptions Act.

The advice from the UK Department of Trade and Industry and the UK enforcement officers is that most components and sub-assemblies should not be CE Marked.

If a product is to bear the CE Marking, there must be objective evidence in the DATA FILE. If a product will not bear the CE Marking, it may still be intended to be built into something that will bear the CE Marking.

The one thing that is clear is that there is nothing trivial about the question of CE Marking. There is much more to it than is immediately apparent.

COMPLIANCE PROVING

There are two routes to compliance – the `Standards’ and the `Technical Construction File’ approaches. The best advice is to discuss your particular needs with your EMC consultant or Test-House for help on how best to reduce your timescales and costs, because there are many pitfalls. There are fundamental things that companies need to know in the testing of products. It is pertinent to ask: `Was the product tested good, bad or nominal? Unless a manufacturer knows that simple piece of information, he can be either making non-compliant products or over-engineering perfectly acceptable products. Re-testing by measuring a few known peaks will provide confidence and the evidence of `due diligence’ which is required.

DIRECTIVES AND STANDARDS

If we consider that a machine can be either potentially hazardous or potentially lethal then we could reasonably expect the Machinery Directive to treat the two `classifications’ differently.

Annex D of the Machinery Directive contains a list of machines adjudged to warrant greater consideration, including saws, compacting equipment, lifts and safety components. The Machinery Directive allows the `producer’ to conduct all compliance reviews and tests upon products not listed in Annex D.

The Machinery Directive requires the involvement of an `Approved Body’ before we can affix the CE Marking to any `Annex D’ machine. The Low Voltage Directive, on the other hand, currently makes no such distinctions and allows the `producer’ to conduct all compliance reviews and tests upon his products no-matter how hazardous they might be.

The choice of which Directive to adhere to comes down to the principal hazard. The next step is to choose a standard against which to achieve compliance.

Choosing a standard against which to achieve EMC and Machinery Directive compliance is not too difficult, but a common error made in selecting the LVD standard is that (like the EMC Directive) more than one standard may be applicable.

As an example, consider a controller that will control 3-phase equipment and will be connected to a PC. There are several aspects to examine here, including the 3-phase supply, the controller (PLC), the operator and service personnel, external connections, and the personal computer interface. Most of these areas will be covered by any PLC safety standard, however the PC interface will be outside their scope. This is because the Information Technology Equipment standard requires a higher level of `Operator’ protection. Therefore all digital connections must be assessed to EN 60950.

COMPLETE ASSURANCE?

Unfortunately, those hoping the CE Marking represents ultimate peace of mind are going to be disappointed. It is not a safety mark and must not be interpreted as such. It is an unfortunate fact that a high percentage of the Self-Assessed products will fail to comply with the Low Voltage Directive. A common problem is use of equipment designed for 60Hz supplies in the EU which uses 50Hz. An example I saw was a modem, whose transformer in the power supply needed replacement, being hot and noisy. When I replaced it, I found the yellow insulation tape had turned brown, which implied potential fire and electric shock hazards. Another example was the windings on a motor which I measured overheating to 150 degrees C. The US manufacturer first insisted it could not possibly get that hot, then phoned back to say that he had repeated my tests and agreed with the results. Both the modem (and its power supply) and the motor were CE Marked and came from blue chip companies, and both had been deliberately placed on the EU market.

It is also common to see earthing non-compliances. Earthing is fundamental to most electrical equipment yet it is common to see earth and mechanical fixings using the same hardware, open-tongue termination (instead of ring-terminations), single crimp joints, no locking hardware, bonding `through’ paint or anodising, and daisy-chained earth connections.

COMMON NON-COMPLIANCES

Some of the common problems are all too prevalent, but really should not occur. I frequently see equipment where mains wiring wanders back and forth, coupling emissions into and from the equipment, until it eventually finds an EMC filter. This is not good! Mains connection to the filter should be kept short and away from all other leads.

Inadequate insulation is another common problem. Most `approved’ terminal strips will provide `basic’ insulation between adjacent terminals and are suitable for connecting Live, Neutral and Earth. However, if we now include Safety Extra Low Voltage (SELV) connections within the same terminal strip we may not have adequate `creepage’ distance (>8mm) between the hazardous and SELV terminals. It is not a good idea to combine mains and SELV connections: where possible, separate connectors should be used.

The Author

Gregg Kervill lectures and offers consultancy services on both sides of the Atlantic and in Asia; he has presented papers in Washington DC, at Euro-EMC and at many of the UK EMC Clubs and Chambers of Commerce.

With 20 years R&D experience behind him, he founded GKCL in 1993 to offer essential support services and products for professional design engineers and managers

{{Should the CE Mark be applied?

Question Answer

What is the business objective? To seel components

Who specifies your product in the design? Design engineers

Will they need to apply the CE Marking? Yes

Will they need to complete a `DATA FILE’containing details of the electrical,thermal, flammability and othercharacteristics of your component? Yes

Do you provide them with the necessarytechnical information? No

Do you think it might give your companya marketing advantage if you providedthe necessary information? Yes}}