Field Evaluation of Slip-Dependent Thermal Model for Motors with High-Inertia Starting

This paper evaluates the advantages of using the slip-based thermal model with data collected from an actual field installation. The paper presents information on motor starts before and after installation of the new motor protection technology. Improvement claims are based on the first order thermal model, enhanced with the calculation of slip and rotor resistance to improve accuracy of its starting element. This improved accuracy calculates more precise per-unit rotor temperature, allowing longer start times than other methods. The new model uses current, voltage, and algorithm to calculate slip and rotor resistance from motor apparent impedance. The evaluation includes a start report from a field installation.