Can EMC compatibility be achieved by just assembling EMC compliant components..?
Question:
Regarding Electro Magnetic Compatibility (EMC) on a generating set is it acceptable to :-
a) Take individually approved components and CE marked components and;
b) using the component manufacturer’s instructions/application notes and engineering skill and judgement to assemble them in a way that we believe they would be EMC compliant as an assembly;
c) then place the complete generating set on the market as EMC compliant without specific tests?
Response:
Regarding the question, in a word, NO.
The EMC Directive (the Electromagnetic Compatibility (EMC) Regulations 2006) allows for testing the worst case machine of each family (the manufacturer should document the rationale behind this choice within their Technical Documentation). This worst case test can then be used to represent the other variants of the same machine family. Manufacturers may use this worst case approach to reduce test costs, but should also accept the increased risk it presents over testing every machine configuration (which is also an option).
A collection of individually EMC compliant components does not guarantee an EMC compliant assembly of those components.
It is not normally acceptable to take a series of electromagnetically compatible components, to assemble these into a product and to assume that the product will then meet electromagnetic compatibility constraints without testing, since wiring will have been added along with other fortuitous electrical and magnetic paths through the structure of the product that will influence electromagnetic performance. This wiring and the fortuitous paths will provide potential aerial inputs and outputs for both emissions of radiations and conductions of interference into the apparatus and cannot be evaluated accurately without testing.
Where a product has options, unless all option combinations are to be individually tested, the minimum requirement would be to take a fully optionalized product through the appropriate EMC emissions and immunity testing with all options enabled and functional. The manufacturer should provide a technical rationale for this test methodology in the technical documentation.
In this case, a product with a lesser number of options is likely to have fewer components and shorter wiring paths and provided that good wiring practice has been observed with respect to the observance of maintaining good earthing of shielding and components, regardless of component count; then a sound technical argument should be able to be presented for this methodology of testing the most complex product only.
Important Note
Absence of case law means that much of this advice is based on current understanding, a number of draft documents and is subject to revision at any time. Any decisions should be verified with an expert on European Law on a case-by-case basis.