Current fault signatures of Voltage Source Inverters in different reference frames

This paper considers different current patterns used to identify the correct fault signatures in Voltage Source Inverters (VSI). At the beginning, the Authors consider the currents patterns from which a simple or a double fault can be encompassed both in the case of controllable device only or with its free wheeling companion diode. After the discussion of diagnosis algorithm suitable for electrical drives and principally based on a persistent near zero current condition current in the natural phase reference frame, the stationary reference frame is then considered as a tool to identify both the faulted phase as the device or various combination of faulted devices. On the contrary, the Authors finally demonstrate as in a rotating reference frame such informations are irretrievably lost. In the rotating reference frame only the presence of a open circuit fault can be detected without further elements to decide what phase or devices are then involved in. For this reason the stationary system appears the only satisfactory tool to provide all the diagnostic information both in order to schedule a maintenance operation or to hypothesize a reconfiguration of the VSI with the purpose of its possible fault tolerant operation.