Monitoring system for electrical machine star-connected stator windings

摘要

The monitoring system detects the zero voltages at the terminals of the star-connected stator windings, with evaluation of their operating frequency component for provision of a release signal, with a second release signal provided by filtering out harmonics from the zero voltages to provide an intermediate value (MZ1). The detected zero currents in the stator windings are similarly filtered to provide a second intermediate value (MZ2) with comparison of the phases of both intermediate values, to provide a phase angle compared with a defined range to obtain a release permit signal (AV1). An auxiliary value obtained from at least one intermediate value is compared with a threshold to provide a further release permit signal (AV2), the second release signal supplied in response to both release permit signals.