Power converter fault diagnosis in SRM drives based on the DC Bus current analysis

This paper presents a new fault diagnostic technique applied to switched reluctance motor (SRM) drives. A fault is detected when the measured amplitude of the DC bus current differs from its expected amplitude, assuming normal operating conditions. The information about phase currents amplitudes and the control states of all power switches permit to easily estimate the amplitude of the power converter supply current, since an asymmetric bridge converter is used. Open-and short-circuit fault occurrences in the converter power switches are presented. The proposed technique can early detect these fault occurrences and can also, in almost situations, identify not only the affected motor phase but also the faulty element. A short-circuit fault in a converter power switch of a SRM drive does not necessarily causes a short-circuit in the DC bus, unlike to what happens in many other converter-fed electrical machine drives. On the other hand, although a converter power switch open-circuit fault can be easily detected by the observation of the phase currents, the identification of the faulty element becomes impossible to achieve, if only phase currents are measured. This information is of paramount importance in the development of fault tolerant power converters.