Identification Method of Current Conditions Suitable for Synchronous Machines Having Multiple Operating Points

Abstract

To perform finite element analysis (FEA) for estimating the characteristics of synchronous machines (SMs), a current condition corresponding to an operating point is necessary as an analysis input. Accurate identification for the current condition is a difficult problem because it is strongly susceptible to magnetic saturation, e.g., the magnetic interaction between d- and q-axes. Especially in a wound-field SM, its flexibility makes the identification more complicated; in other words, three independent variables, such as the amplitude and phase of armature current and amplitude of field current, have to be identified for SMs, whereas two variables are required for a permanent magnet SM or synchronous reluctance machine. Thus, numerous researchers have studied construction of the identification method. This paper proposes a novel identification method for the current condition of wound-field SMs using saturation functions defined by the flux maps. It is demonstrated that the proposed method can correctly identify a large amount of current conditions in a short computation time. In addition, the influences of magnetic saturation on the characteristics of the SM were investigated by comparing the identification results obtained by the linear and non-linear FEA. It is revealed that the magnetic saturation drastically affects the current condition and must be considered in the identification methodology.