A prediction model for electromagnetic interferences radiated by an industrial power drive system

Power conversion systems and in particular power drives are now present in a large number of applications and environments. The switching operations of power drive systems (PDS) are sources of radiated and conducted electromagnetic interferences that give rise to problems of electromagnetic compatibility with other systems. This work proposes an efficient numerical technique to evaluate the radiated emissions due to a PDS, taking into account the radiation from intentional apertures (i.e. those for ventilation). The power section of the PDS is simulated by a combination of radiating dipoles in which the current is known. The radiated EM field induces currents on the PDS metallic cage surface that in turn radiate outside the cage. These currents are computed by an efficient numerical method known as partial element equivalent circuit technique. Finally an equivalent EM model for the apertures needed for the air cooling and ventilation of the device is given. The proposed prediction model is hence able to predict the total radiated emission from a PDS in its design stage in order to fulfil the electromagnetic compatibility requirements called by the international standards.