The circuit parameters involving stray load loss and harmonic torques of high-speed induction motors fed by inverters are determined by both finite-element method and experiments, respectively. In the finite-element method, the parameters are directly determined from the electromagnetic field distribution of the motors under load conditions. On the other hand, in the experiment, the parameters are determined from no-load, locked rotor, and load tests. The characteristics calculated by the proposed circuits are compared with those of the measurement in order to confirm the validity and usefulness of the proposed circuit. It is clarified that the accuracy of the calculated characteristics is significantly improved by the proposed circuit as compared to the conventional circuit, particularly under high-speed conditions.