Dynamic Unbalanced Pull from Field Winding Turn Short Circuits in Hydropower Generators

Abstract

Field winding interturn short circuits create an asymmetric air gap flux density and unwanted unbalanced magnetic pull. The unbalanced magnetic pull and flux density distribution resulting from field winding interturn short circuits are investigated both experimentally and through numerical modeling. Due to the unbalanced magneto motive force from north and south poles in the machine, an odd/even effect in the flux density levels is obtained. The occurrence of parallel stator branches combined with a field winding short circuit gives rise to circulating stator currents that has a net flow in the direction of the pole with interturn short circuit and produces an additional unbalanced magnetic pull harmonic force component with twice the rotational frequency.

Keywords:

• magnetic pull
• field winding short circuit
• synchronous generators