Numerical field calculation of stator winding faults in synchronous machines

Abstract

PurposeThe purpose of this paper is to describe a systematic investigation of the currents, torques and other electromagnetic quantities in a machine after different short circuits by the means of coupled numerical field and network calculation. The behaviour of a synchronous machine after a stator‐winding fault still is a little known issue. Nevertheless, the occurrence of winding faults can damage the stator winding of the machine severely and may also destroy the whole stator core. Therefore, there exists a strong need for reliable calculation methods for the evaluation of these faults, e.g. the reconstruction of the details of an accident.Design/methodology/approachThe paper discusses an analytical approach which calculates all possible winding connections when absence of nonlinear material behaviour is assumed and nonlinearity is only considered by adjusting the inductances after solving the differential equations. In the following, a more accurate method is given by the numerical field calculation, considering a two‐dimensional time variant permeability distribution on the cross‐section of an electrical machine.FindingsFirst results of transient time‐stepping calculations of short circuits with special respect on winding currents and radial forces on the rotor are presented.Practical implicationsThe approach presented in this paper can be applied in the field of R&D for the dimension of electrical machines and its protection system as well as for the investigation of possible sources of an occurred machine failure.Originality/valueThe bulk of publications that contribute to the topic of inner winding faults are comprised of derivations of analytical models with the assumption of linear material behaviour. The paper puts strong emphasis on the consideration of the nonlinearity.