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The benefits and drawbacks of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding interturn and broken rotor bar faults, are presented in this paper. It was perceived that this motor had the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Hence, this motor was anticipated to make a useful test bed for evaluation of the efficacy of existing and new motor fault diagnostics techniques and not the study of insulation failure mechanisms. Accordingly, it was anticipated that this reconfigurable motor would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions are presented in this paper, including issues associated with rotor bar-end ring contact resistances that showed the drawbacks of this motor in so far as emulation of rotor bar breakages. However, emulation of stator-turn fault scenarios was successfully accomplished. Index Terms--Condition monitoring, fault diagnostics, fault emulation, induction motors, reconfigurable motors, rotor broken bar faults, stator winding interturn faults.

A new method for the fault diagnosis of a broken rotor bar and interturn short circuits in induction machines (IMs) is presented. The method is based on the analysis of the three-phase stator current envelopes of IMs using reconstructed phase space transforms. The signatures of each type of fault are created from the three-phase current envelope of each fault. The resulting fault signatures for the new so-called 'unseen signals' are classified using Gaussian mixture models and a Bayesian maximum likelihood classifier. The presented method yields a high degree of accuracy in fault identification as evidenced by the given experimental results, which validate this method. Index Terms--AC motor drive systems, broken bars, envelope detection and classification, fault diagnosis, induction machines (IMs), induction motors, interturn short circuits.

A robust interturn fault diagnostic approach based on the concept of magnetic field pendulous oscillation, which occurs in induction motors under faulty conditions, is introduced in this paper. This approach enables one to distinguish and classify an unbalanced voltage power supply and machine manufacturing/construction imperfections from an interturn fault. The experimental results for the two case studies of a set of 5-hp and 2-hp induction motors verify the validity of the proposed approach. Moreover, it can be concluded from the experimental results that if the circulating current level in the shorted loop increases beyond the phase current level, an interturn fault can be easily detected using the proposed approach even in the presence of the existence of motor manufacturing imperfection effects. Index Terms--Broken-bar, condition monitoring, induction motor, interturn short circuit, stator fault, transient modeling.

The effects of load level on the ability to diagnose broken bar faults in squirrel-cage induction motors are studied in this paper. The pendulous oscillation of the rotor magnetic field orientation is implemented as a fault signature for rotor fault diagnostic purposes at steady-state operations. Moreover, the effects of load level on the low-side band component of the stator current spectrum, and associated diagnostic difficulties in this approach particularly in the presence of motor operation from pulsewidth-modulation drives, are reported as well. These investigations were performed through testing 2-hp and 5-hp induction motors over a wide range of load levels and control drives. The results of these tests and investigations demonstrate the efficacy of the pendulous oscillation signature as a diagnostic means that can be used for a wide range of motor operating conditions. Index Terms--Broken bar diagnosis, induction motor fault detection, pendulous oscillation, rotor magnetic field orientation, swing angle.

A new technique based on rotor magnetic field space vector orientation is presented to diagnose broken-bar faults in induction machines operating at steady state. In this technique, stator currents and voltages are used as inputs to compute and subsequently observe the rotor magnetic field orientation, which has a more significant 'swing-like' pendulous oscillation in case of broken-bar faults than in healthy operation. It will be shown here that the range of this 'pendulous oscillation' is a function of the number of broken bars. Also in this technique, it was found that an inter-turn shorted stator-winding fault, which exhibits similar pendulous oscillation, could be distinguished from rotor broken-bar faults through the use of a variance index. In order to validate this method, experimental evidence is given here for several broken-bar cases in a 2-hp three-phase two-pole squirrel-cage induction machine. Index Terms--Fault diagnosis, induction machines, rotor magnetic field space vector, swing-like pendulous oscillation.

This paper develops the foundations of a technique for detection and categorization of dynamic/static eccentricities and bar/end-ring connector breakages in squirrel-cage induction motors that is not based on the traditional Fourier transform frequency-domain spectral analysis concepts. Hence, this approach can distinguish between the 'fault signatures' of each of the following faults: eccentricities, broken bars, and broken end-ring connectors in such induction motors. Furthermore, the techniques presented here can extensively and economically predict and characterize faults from the induction machine adjustable-speed drive design data without the need to have had actual fault data from field experience. This is done through the development of dual-track studies of fault simulations and, hence, simulated fault signature data. These studies are performed using our proven Time-Stepping Coupled Finite-Element-State-Space method to generate fault case performance data, which contain phase current waveforms and time-domain torque profiles. Then, from this data, the fault cases are classified by their inherent characteristics, so-called 'signatures' or 'fingerprints.' These fault signatures are extracted or 'mined' here from the fault case data using our novel Time-Series Data Mining technique. The dual track of generating fault data and mining fault signatures was tested here on dynamic and static eccentricities of 10% and 30% of air-gap height as well as cases of one, three, six, and nine broken bars and three, six, and nine broken end-ring connectors. These cases were studied for proof of principle in a 208-V 60-Hz four-pole 1.2-hp squirrel-cage three-phase induction motor. The paper presents faulty and healthy performance characteristics and their corresponding so-called phase space diagnoses that show distinct fault signatures of each of the above-mentioned motor faults. Index Terms--Artificial intelligence, data mining, diagnostics through current waveforms, dynamical systems analysis, electric drives, fault diagnosis, induction motors, state-space methods, time series, time-stepping finite elements.

This paper develops the fundamental foundations of a technique for detection of faults in induction motors that is not based on the traditional Fourier transform frequency domain approach. The technique can extensively and economically characterize and predict faults from the induction machine adjustable speed drive design data. This is done through the development of dual-track proof-of-principle studies of fault simulation and identification. These studies are performed using our proven Time Stepping Coupled Finite Element-State Space method to generate fault case data. Then, the fault cases are classified by their inherent characteristics, so-called 'signatures' or 'fingerprints.' These fault signatures are extracted or mined here from the fault case data using our novel Time Series Data Mining technique. The dual-track of generating fault data and mining fault signatures was tested here on three, six, and nine broken bar and broken end-ring connectors in a 208-volt, 60-Hz, 4-pole, 1.2-hp, squirrel cage 3-phase induction motor. Index Terms--Artificial intelligence, data mining, diagnostics through torque profiles, dynamical systems analysis, electric drives, fault diagnosis, induction motors, state space methods, time series, time stepping finite elements.

This paper reviews recent advances in the state of the art of applying three-dimensional finite-element (3-D-FE) magnetic field computation techniques to the analysis and quantification of parameters and performance of permanent magnet (PM) brushless dc motors as components of brushless dc drives. The application of the powerful 3-D-FE formulation based on the coupled magnetic vector potential-magnetic scalar potential (CMVP-MSP) concept to a case study PM brushless dc motor with skewed permanent magnet mounts is reviewed and summarized. This large-scale simulation of such a motor drive system is shown here to be successfully implementable using workstation type computer environments.

This paper describes how a comprehensive time-stepping coupled finite-element phase-flux-linkage-based state-space modeling approach can be used for characterization of induction motors in adjustable-speed drives. The model implemented the faster indirect and iterative coupling approach based on the curl-curl nondiffusion equation rather than the direct coupling approach, which is based on the curl-curl diffusion equation. The model presented in this paper is capable of rigorously modeling the effects of magnetic nonlinearities and space harmonics due to the machine magnetic circuits' topology and winding layouts, time harmonics resulting from electronic switching of inverters, as well as the synergistic interaction between these time and space harmonics. This includes the presentation of a unique approach for the calculation of electromagnetic torque by means of a concept of energy balance computed from instantaneous magnetic field solutions calculated at each time sample in an ac cycle. This approach reveals higher content of torque ripples than given by more conventional approaches to torque calculations. The results of motor drive performance simulations and corresponding test results are shown to correlate well here with current waveforms and torque averages. This includes sinusoidal excitation, and six-switch inverter excitation with pulsewidth modulation switching pattern, respectively. The analytical/computational soundness, robustness, and capability for design assessments and modifications are detailed in a companion paper. Index Terms - Adjustable-speed drives, finite element, induction motors, phase ABC flux linkage frame of reference, pulsewidth modulation, state-space model, time stepping.

Focuses on the optimization of the skew angle of rotor magnetic poles in permanent magnet brushless direct current machines. Armature winding flux linkages and related induced electromagnetic field sensitivity; Use of stored energy and excitation perturbation methods; Inverse problem methodology.

Features a study on the performance characteristics of induction motor adjustable-speed drives using a time-stepping coupled finite-element state-space model. Effects of machine geometry and magnetic wedging motor performance; Effects of stator slot opening on torque profiles; Effects of pulsewidth modulation carrier frequency on performance characteristics of induction motor drives.

Part II. Details the formulation and application of a time-stepping coupled finite element-state space (CFE-SS) model of salient-pole synchronous machines that supply electronically commutated rectifier loads. CFE-SS generator-rectifier load modeling environment; Model of finite element; Balanced rectifier load simulation and results; Unbalanced rectifier load simulation and results; Iron core loss computation; Conclusions.

Part I. Focuses on a time-stepping coupled finite element-state space (CFE-SS) approach develop for synchronous machine unbalanced impedance load and balanced/unbalanced rectifier load operation. Natural ABC frame of reference; State-space model and lumped parameter circuit representation; Time-stepping finite element model; CFE-SS modeling environment; CFE-SS model for unbalanced impedance loads; CFE-SS simulation results; Iron core loss computation; Conclusions.