Determination of Synchronous Reactance and No-Load Saturation Curve of Synchronous Machines by dc Test Considering Magnetic Saturation Effect

dc Tests can accurately determine the unsaturated synchronous machine-equivalent circuit constants by a simple standstill test. This paper presents two improved dc tests that account for the magnetic saturation of the stator iron core by the main flux. These tests are tentatively named Step Response Test (I) and Step Response Test (II). The former can predict the incremental d-axis synchronous reactance by performing a Fourier transform of the voltage and current measured when a small step voltage is applied to the two armature terminals as a field current flows. The latter can determine the incremental d- and q-axes synchronous reactances by the same Fourier transform of the voltage and current measured when a small step voltage is applied to the two armature terminals as an armature current flows. In addition, this paper introduces a new method to calculate not only the static d- and q-axes synchronous reactances but also the no-load saturation and short-circuit characteristic curves. This new method does not require the results from any additional tests including the rotational driving tests and dimensional information, which can only be obtained from the manufacturer. To demonstrate the validity of the proposed method, results of an experiment using 10-kVA laminated synchronous machines with damper winding are presented. (C) 2014 Wiley Periodicals, Inc.