Out-of step and single phasing protection of synchronous chipper motors

Abstract

Chipper motors in pulp and paper mill environment are of special design-the stability on impact loads is one important consideration. The power factor under normal operation will continuously swing due to varying loads. The paper describes guesswork free rigorous calculations of pull out (out-of-step) power factor based on the parameter of an actual installation. Single phasing is rather a rare occurrence; however, such an event has been experienced in an installation due to overheating and arcing at the fuse clips in a NEMA E2 starter of a chipper motor. Discussions on single phase protection of synchronous motors and recommended settings are provided.