Low-Cost Motor Drive-Embedded Fault Diagnosis - A Simple Harmonic Analyzer

The reference frame theory and its applications to fault diagnosis of electric machinery as a powerful tool to find the magnitude and phase quantities of fault signatures are explored in this paper. The core idea is to convert the associated fault signature to a dc quantity, followed by calculating the signal average value in the new reference frame to filter out the rest of the signal harmonics, i. e. its ac components. Broken rotor bar and rotor eccentricity faults are experimentally tested both offline using the data acquisition system, and online employing the TMS320F2812 DSP to prove the efficacy of the proposed tool. The proposed method has been theoretically and experimentally proven to detect the fault harmonics and determine the existence and the severity of machine faults. The advantages of this method include the following: (1) no need to employ external hardware or a PC running a high level program; (2) provides instantaneous fault monitoring using a DSP controller in real time; (3) embedded into the motor drive; thus, readily available drive sensors and the core processor are used without employing additional hardware; (4) no need to store machine currents data, and thus no need for large memory size; (5) very short convergence time capability; (6) immune to non-idealities like sensor dc offsets, imbalance, etc.