Abstract
This article describes a practical method for predicting the distribution of electric potential inside an electrical machine’s winding based on design data. It broadens the understanding of winding impedance in terms of inter-winding behavior and allows to properly design an electrical machine’s insulation system during the development phase. The predictions are made based on an frequency-dependent equivalent circuit of the electrical machine which is validated by measurements in the time domain and the frequency domain. Element parameters for the equivalent circuit are derived from two-dimensional field simulations. The results demonstrate a non-uniform potential distribution and demonstrate that the potential difference between individual turns and between turns and the stator core exceeds the expected values. The findings also show a link between winding impedance and potential oscillations inside the winding. Additionally, the article provides an overview of the chronological progression of turn-based models and shows how asynchronous multiprocessing is used to accelerate the solution process of the equivalent circuit.
Highlights
As presented in a recently published article [1], research concerning non-uniform potential distributions in electrical machine windings dates back to 1930 [2] and even back to 1902 for transformers [3]
The methodology consists of the following key aspects: two different field simulations are executed. Those provide input parameters for the equivalent circuit model, which is solved in the frequency domain, and the result is multiplied with an input signal
The methodology presented is capable of predicting the impedance of an electrical machine over a wide frequency range
Summary
As presented in a recently published article [1], research concerning non-uniform potential distributions in electrical machine windings dates back to 1930 [2] and even back to 1902 for transformers [3]. It was observed that non-uniform potential distributions occur during voltage transients at the machine terminals which impose abnormal stress on the insulation. The successive work of scientists produced models of increasing complexity and better understanding of cause and effect of non-uniform potential distributions [4,5,6,7,8,9]. Frequency-dependent circuit elements are approximated by ladder networks These ladder networks increase the overall count of circuit elements. Depending on the chosen order of approximation, this leads to increased computation times. A direct implementation of the presented model in the frequency domain is perused
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