EMC Directive 2004/108/EG

Since most machines have an electrical installation, Electromagnetic Compatibility Directive 2004/108/EG is also applicable. This directive addresses the possibility that a machine’s control unit could be sensitive to interference signals and may also transmit interference signals itself. This refers, with the unavoidable use of a few difficult words, to the immunity and the emission of an electrical installation. This EMC Directive is further elaborated in a number of harmonized European standards in which a distinction is made between electrical installations and electrical devices intended for household use or for light or heavy industry.Generally, these standards indicate the limits within which the electrical device or machine may not cause interference.

If we want to define electromagnetic compatibility in simple terms, then we can formulate the description as follows: an electrical installation may not cause interference nor be affected by interference.[1]
In practice, interference caused more problems in the past than it does now. Years ago, a TV showed signs of interference when a motorcycle drove by. The first machine PLCs would sometimes dare to act strangely if a transformer was set up in their vicinity. We have known about the principle of electromagnetic fields for a long time now—Mr Faraday invented the Faraday cage in the 1830’s.
This cage was intended to act as shield for electromagnetic waves.

The EMC Directive has been specially formulated to provide obligatory guidelines for the manufacturers of electrical components in order to ensure that their equipment does not cause interference or is not affected by interference.

Nowadays when we build a new machine, the switch box of the machine is filled with all kinds of electronic components which can be sensitive to electromagnetic waves. Think, for example, of frequency regulators, switch-mode power supplies, PLC’s and safety PLC’s. As a matter of assurance, each switch box should be checked (measured) for EMC sensitivity. Because this is almost impossible for many machine builders, the EMC Directive allows for the assumption, on the basis of all of the EMC Declarations from the component suppliers, that the assembly complies with the EMC Directive.
This assumption is based on the EMC= EMC1+EMC2+EMC3+EMC4 principle. That is why it is important that correctly approved components are used when building a switch box and that the person building the switch box has sufficient expertise to correctly assemble the components. Even stripping wires too long or assembling components with a partially exposed wire can cause EMC sensitivity.

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