An Alternative Run-Up Strategy for Salient Pole Wound Field Synchronous Machines

Salient pole wound field synchronous motors find many industrial applications, thanks to their favorable characteristics: reactive power regulation, stiff mechanical characteristic, and overall outstanding efficiency. Nevertheless, their competitiveness toward the induction motors, especially for medium and small power sizes, depends crucially on their capability to be asynchronously started as well. Regrettably, the asynchronous run-up of a synchronous motor can be sometimes very problematic because of thermal issues, torsional vibrations, and grid voltage disturbances. This article presents an alternative method of starting salient pole wound field synchronous machines by activating the field winding in a special manner, which makes it possible to mitigate the three problems at once. The suggested method is validated through a two-dimensional finite elements simulation and by starting a 60-kVA prototype generator. The requirements for the application of the proposed run-up strategy are critically discussed together with related pros and cons.