EMC in power electronic devices: radiated emissions from a silicon controlled rectifier

During the last decade, great achievements in the field of power electronics have significantly contributed to its promotion in all areas of engineering. However, its evolution to an indispensable factor in today´s industrial applications has also involved a certain number of problems which have not yet been studied thoroughly or completely solved. For instance, the electromagnetic interference emanating from power converters in particular frequency ranges. The aim or this paper is to identify the main sources of radiated noise emission from a silicon controlled rectifier (SCR) by means of the correlation between common mode currents and electromagnetic field measurements. Moreover, an equivalent radiation model is to be developed enabling emission level prediction in the design phase when compliance of the device with international standard regulations is to be verified. Direct measurements of common mode current spectra and the E-field emanating from a SCR bridge allow the correlation between them to be found, thus identifying the origin of the radiation. Both time domain waveforms and the corresponding spectra are monitored for several operation points at different locations on the set-up. Field measurements are also carried out for each operating point for vertical and horizontal polarization. The study has yielded a number of interesting results concerning the identification of the main common mode current propagation paths and their radiating effects