The Hybrid Method for Parameters Estimation of a Single-loop Equivalent Circuit of Induction Motors

As a result of the analysis of existing methods for determining the equivalent circuits parameters, it was ascertained that not taking into account the initial data from the intermediate slip range 1 > s > s
max
when synthesizing equivalent circuits for induction motors with one- and especially dual-circuit rotor leads in some cases to the appearance of "humpback" or dips in their starting characteristics. The paper proposes a hybrid parameter estimation method for a T-shaped single-loop equivalent circuit of an induction motor with a squirrel-cage rotor, based on a combination of iterative algorithm, associated with the solution of a nonlinear algebraic equation system (basic algorithm), and numerically more stable non-iterative calculations. The need to use the non-iterative method is associated with the violation of resistance and inductive reactance ratio of the rotor circuit for certain types of induction machines at nominal slip and at slip s = 1, as well as with the problems of obtaining a global extremum when solving nonlinear algebraic equation systems. The performance of the proposed method has been tested for all high-voltage induction motors of thermal condensing power plants power units auxiliaries with rated power of 200 MW and 300 MW, as well as a power unit of a combined-cycle thermal power plant with a rated power of 450 MW.