In the frequently used frequency inverters, which consist of a rectifier (GR) and a pulse inverter (PWR), there are two CM voltage sources. As a result, CM currents are excited by both the GR and the PWR, which overlap. In the case of a frequently used diode GR, the resulting CM currents have frequencies of 150 Hz, 450 Hz, 750 Hz, etc. In the case of a PWR, frequencies in the range of the pulse frequency and its multiples are excited. In addition, excitations from EMC filter circuits can occur, which can then also cause resonant CM currents. Furthermore, harmonics in the mains voltage or asymmetries in the X capacitors can also lead to CM currents, which then flow to PE via the Y capacitors of the EMC filters.

The causes and manifestations (frequencies) of PE/PA currents are very diverse, which makes their understanding and therefore their reduction difficult. In practice, purely phenomenological measurements are often carried out in the form of effective values, which often result in very high values of several tens of A, but naturally in this form do not allow any indication of the specific cause. Often it is not even possible to assign the PE/PA currents to a specific device, let alone define suitable remedial measures.

In the predecessor project “PEPA 1” , the main causes and propagation paths of PE/PA flows were systematically examined for the first time. In this follow-up project “PEPA 2”, the systematic analysis carried out so far will be expanded to include more complex systems, such as those that predominantly occur in practice, thereby completing the understanding of the mechanisms of action and remedial measures. From today's perspective, no further continuation is planned within the framework of the funding from the BMWK.