On December 31st of 2004 the New Directive 2004/108/EC of the European Parliament and of the Council regarding electromagnetic compatibility was published in Offical Journal of the European Union. This Directive replaced former Directive 89/336/EEC of May 1989 introducing some changes mainly focused on the way of application of it.
Both Directives keep same essential requirements about emission and susceptibility and the use of harmonized standards to grant presumption of conformity. EMC Directive is applicable to the majority of electrical and electronic equipments.
The new Directive introduces an important change, the appearance of fixed installations and responsible person for the establishment of them according to essential requirements. Fixed installation means a particular combination of several types of apparatus and, where applicable, other devices, which are assembled, installed and intended to be used permanently at a predefined location.
In a different way than with the rest of electrical or electronic equipments and apparatus, presumption of conformity for fixed installations doesn’t depend on fulfilment of harmonised standards. Then appears the good engineering practices concept. It means, for the starting of a fixed installation it is not needed the CE marking neither the declaration of conformity.
Good engineering practices are the set of techniques commonly used and accepted by sector professionals to reach the protection degree needed according to current state of the art of every moment. All fixed installations have to be done by competent technical personnel who know mentioned good engineering practices.
On the other hand, it is required a legal responsible person for the installation who has all technical documentation that demonstrates that all needed cautions have been taken in order to fulfil essential requirements regarding emission and susceptibility. This documentation will grant presumption of conformity and must be at the disposal of the relevant national authorities for inspection purposes for as long as the fixed installation is in operation.
According to the fixed installation definition, we can easily understand that wind mills are included in this definition. We must not wrongly understand EMC Directive and assume that all internal devices or parts are excluded of applying EMC standards. That is to say, inside of a wind mill there are electrical or electronic devices which have not been designed and constructed for fixed installations only, they can be placed in other equipments as well. In this case, such devices are subjected to demonstrate their presumption of conformity by means of applicable EMC harmonized standards for each case.

   
        This is the case of switched mode power supplies or frequency inverters who convert energy from wind mills in voltages and currents suitable to be injected to the mains network with all needed signal quality requirements in low or medium voltage. These equipments use switching technologies of several kHz for transforming DC or AC voltajes into 50/60 Hz signals. This process, despite the fact it’s highly efficient, is very noisy from the EMC point of view and so that it is necessary to incorporate an EMI filter at its output to avoid that noise can affect rest of equipments of wind mill and to prevent that noise can reach mains network.
Applicable EMC standards for low frequency disturbing voltages (conducted emissions) for this type of equipments are normally EN55011 for Industrial, Scientific and Medical or generic EMC standard EN61000-2-4 for industrial environments.
The fulfilment of requested maximum levels (limits) according to conducted emission EMC standards together with the high level of emission from frequency inverters implies that EMI filters for these applications must be very special. EMI Filters for wind mills frequency converters are normally designed with filtering diagrams that allows them to provide very high insertion loss (attenuation) around 80-100 dB in a wide frequency range (from few kHz up to several MHz).
On the other hand, the nominal current of these filters is very high due to the current level that current wind mills have. If we consider the needed electrical diagram of filter for reaching needed insertion loss levels together with high nominal current that must flow across the filter and will determine size of internal parts it’s easy to realise that final size and weight of filter could be excessive. This fact would be a big disadvantage when installing the filter inside of wind mill, where volume and weight are highly important.

                                               Results without filter

        Since several years ago, Premo EMC has a Wide range of specific filters for frequency inverters that are installed in wind mills. This range of filters has been developed bearing in mind factors like insertion loss, volume, weight, connections, price, etc. In cooperation with magnetic materials development centres, Universities and manufacturers. Thanks to this cooperation and the use of resulting materials, we developed new specific EMI filters with expected insertion loss, volume, weight and price.

FVDT EMI filter series has been specifically designed for frequency converters placed in wind mills. Its current range goes from 180 Amps up to more than 1000 Amps with different voltage values (520 and 720 Vac). In addition, Premo EMC has fixed and mobile EMC laboratorios to be able to perform needed conducted emission tests for technical constructional file for fixed installations responsibles.