System and method for determining stator winding resistance in an AC motor

Abstract

A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

Description

[0001] Cross References to Related Applications [0002] This application claims priority to US Provisional Application 60 / 932,743, filed June 4, 2007, which is incorporated herein by reference. [0003] government license [0004] This invention was made at least in part with Government support awarded by the United States Department of Energy under Contract No. DE-FC36-04GO14000. The government may have certain rights in this invention. technical field [0005] The present invention relates generally to alternating current (AC) electric motors, and more particularly to systems and methods for determining stator winding resistance for thermal protection of AC electric motors. Background technique [0006] Thermal protection is an important aspect of motor condition monitoring because motor failures are often related to stator winding insulation. It is generally assumed that the life of the motor is reduced by 50% for every 10°C temperature rise above the acceptable stato...

AI Technical Summary

Problems solved by technology

While this method can be accurate and robust to cooling conditions and changes in motor parameters, it has the disadvantage of being invasive, as the additional DC injection current needs to be installed in series with one of the motor leads

In addition, previous signal injection-based methods generally cannot be directly applied to electric motors exceeding 100hp due to the current limitation of semiconductor devices.

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