KRONS REDUCTION METHOD APPLIED TO THE TIME-STEPPING FINITE-ELEMENT ANALYSIS OF INDUCTION MACHINES

The behavior of large induction motors during transient as well as ste ady state running conditions is of significant interest to the power i ndustry. A variety of analytical predictive tools are employed to aid the design and predict their operation under transient and steady stat e conditions. One of the most powerful methods for investigating the t ransient behavior of induction machines is a coupled time stepping fin ite element analysis which can combine electromagnetic fields, circuit s and mechanical systems [1, 6]. Due to the complexity of the finite e lement induction machine model and the resulting large number of descr ibing equations, the computation time required for such. programs to s olve practical problems becomes a major limitation. This becomes even more of a concern when different design options or operating scenarios are evaluated. This paper presents a strategy to reduce the required running time in order to make a parametric study of induction machines such as the assessment of different design options feasible, This is accomplished by reducing the number of finite element equations that m ust be solved while maintaining the same level of accuracy of solution s. This method is based on Kron's network reduction work for linear sy stems and has successfully been applied to large lumped parameter mode l of transformers [2]-[3]. This paper illustrates the reduction method by comparing the flux density in the air gap for a complete FEM model of an induction machine to that of the reduced model. The results are essentially identical with a reduction in computational time of appro ximately 71%.