Simple realtime condition monitoring tools for low-cost motor drives
ABSTRACT In this paper, two simple digital signal processor (DSP)-based motor fault signature detection techniques are presented. First, the reference frame theory and its applications to fault diagnosis of electric machinery are introduced. Second, phase sensitive detection (PSD) of motor fault signatures is presented. Both techniques provide very simple and robust way to find the magnitude and phase of the specified fault signatures in the line current. Particularly, PSD has a powerful line current noise suppression capability while detecting the fault signatures. Various faults are experimentally tested both offline using the data acquisition system, and online employing the TMS320F2812 DSP to prove the efficacy of the proposed tools. The advantages of these methods 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. ; (7) no need for a notch filter to filter out the fundamental harmonic; (8) steady state or stationary current signal assumptions are not necessary; (9) a familiar concept for motor control engineers; and (10) applicable to all multi-phase and single phase motors.
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ABSTRACT: This paper examines the behavior of a three-phase induction motors with internal fault conditions under sinusoidal and nonsinusoidal supply voltages. This includes two types of faults, rotor broken bar and stator faults. Early detection and diagnosis of these faults are desirable for condition assessment, maintenance schedule, and improved operational efficiency of induction motors. The terminal behavior of the induction motor was investigated by coupling the induction motor transient finite-element (FE) model and external electric circuit. Such a model would allow the efficient representation of the induction machine with internal faults. A discrete wavelet transform (DWT) was then used to extract the different harmonic components of the stator currents. The key advantages of the DWT are its ability to provide a local representation (in both time and frequency) of the current signal for normal and faulty modes, and its applicability to nonstationary signalsIEEE Transactions on Magnetics 11/2006; · 1.42 Impact Factor
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ABSTRACT: Recently, research has picked up a fervent pace in the area of fault diagnosis of electrical machines. The manufacturers and users of these drives are now keen to include diagnostic features in the software to improve salability and reliability. Apart from locating specific harmonic components in the line current (popularly known as motor current signature analysis), other signals, such as speed, torque, noise, vibration etc., are also explored for their frequency contents. Sometimes, altogether different techniques, such as thermal measurements, chemical analysis, etc., are also employed to find out the nature and the degree of the fault. In addition, human involvement in the actual fault detection decision making is slowly being replaced by automated tools, such as expert systems, neural networks, fuzzy-logic-based systems; to name a few. It is indeed evident that this area is vast in scope. Hence, keeping in mind the need for future research, a review paper describing different types of faults and the signatures they generate and their diagnostics' schemes will not be entirely out of place. In particular, such a review helps to avoid repetition of past work and gives a bird's eye view to a new researcher in this area.IEEE Transactions on Energy Conversion 01/2006; · 2.43 Impact Factor
Conference Proceeding: On-line diagnostics in inverter fed induction machines using high frequency signal injection[show abstract] [hide abstract]
ABSTRACT: Fault diagnostics for induction machines using an injected high frequency carrier signal is presented and analyzed in this paper. Both stator winding fault and broken: rotor bar detection is covered. Measurement of the resulting high frequency negative sequence current is shown to be capable of detecting both types of faults at their incipient stage. Though sharing similar physical principles to techniques applied to line-connected machines, the use of a high frequency signal is shown to provide important advantages for inverter fed machines, such as providing the same performance and drastically reduced sensitivity to the working condition of the machine, i.e. torque and flux levels, and fundamental excitation frequency.Industry Applications Conference, 2003. 38th IAS Annual Meeting. Conference Record of the; 11/2003