Damper Winding Harmonics Analysis of an Electrically Excited Synchronous Machine at Power Converter Supply

The main purpose of the damper winding in electrically excited synchronous machines is to protect the field winding from large induced voltages caused by unbalanced loads, mechanical oscillations, transient conditions, and harmonics caused by the air-gap field. While electrically excited synchronous machines which are fed via power converter, are not subject to unbalanced loads and mechanical oscillations, they are particularly subject to harmonics in the air-gap field caused by the power converter supply. This paper analyzes the shielding capability of the damper winding at power converter operation as well as the additional power loss. To this aim, the harmonic content of the damper winding for sinusoidal supply, 3-level power converter supply, as well as 15-level power converter supply are analyzed, both theoretically and experimentally using a custom-built electrically excited synchronous machine.