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Large induction motors used in variable speed industrial applications (digging, traction, etc.) undergo dynamic stresses at high power levels. Their lifetime is reduced as compared with constant speed motors and downtime costs are very high. To monitor the condition of such motors, advanced sensor instrumentation is considered, including installation of Hall effect flux sensors inside the motor airgap. Such an advanced instrumentation enables continuous measurement of the airgap flux in both time and space domains simultaneously. This allows for advanced fault detection algorithms. This paper presents a method for early diagnosis of stator turn-to-turn faults and static eccentricity, and differentiation between these two conditions. The paper demonstrates that the proposed method detects, localizes, and quantifies both faults with high accuracy and sensitivity. Furthermore, each fault can be detected at an incipient stage and its development can be predicted. The results of the presented study have been supported by both simulation and experimental results obtained on a laboratory scale induction motor. Based on the results presented in the paper, a real-time condition monitoring system has been developed. [ABSTRACT FROM AUTHOR]

Most of the existing electrical techniques of condition monitoring and fault diagnosis are based on frequency analysis of signals measured externally to the motor. In this paper, it is proposed to add the space dimension to the measured signals by using an array of Hall effect flux sensors installed inside the motor air gap, and to explore the advantages brought by such an instrumentation. The paper presents analytical models of air gap flux density expressed in terms of time and space, for a healthy motor and for a motor with rotor bar faults and mixed eccentricity. Based on these models, the paper proposes a new technique for early detection of rotor bar faults and mixed eccentricity, and for discrimination between them. The paper demonstrates that, with the help of the proposed technique, the severity of each fault and its location relative to rotor or stator can be accurately established. The results of the presented study are supported by simulations and validated by experiments on a laboratory scale induction motor. The formulated fault diagnosis algorithm is suitable for real-time implementation. [ABSTRACT FROM PUBLISHER]

Condition monitoring of induction motors is important for their efficient and reliable operation. Most of the existing electrical techniques of condition monitoring and fault diagnosis are based on current, voltage, vibration, or/and flux measurements external to the motor. This paper proposes an online fault diagnostic system, which is based on measurements of internal main air gap flux density of an induction motor by an array of Hall effect flux sensors. Such an instrumentation is justified for large specialized induction motors with particularly high-reliability requirements. Fundamental theory behind the air gap flux density as a function of time and space, and its distortions introduced by various faults, is reviewed in this paper. Based on this theory, this paper proposes a comprehensive condition monitoring approach to diagnose induction motor faults including stator turn-to-turn shorts, rotor bar damage, and static and dynamic eccentricity, which may be present individually or at the same time. Moreover, the proposed approach not only detects each fault at its early stage but also determines its exact location and severity. The principles proposed in this paper are illustrated by extensive simulations and are experimentally validated on a prototype online condition monitoring system based on National Instruments real-time platform. [ABSTRACT FROM PUBLISHER]

This paper considers recent advances made within the field of electric drives and how this new technology might be best applied within the mining industry. A case study is presented showing simulated results of the performance of the electric drives in a coal preparation plant. The various starting methodologies (resistance starting, fluid coupling, V/f = const, and vector control) are compared within this application. The merits of each method are then discussed with regard to the specific application and other more generic applications within the mining industry. Application of a rotor flux orientation control drive is substantiated, and its superior performance under start and stall conditions to that of the currently implemented system is confirmed by theoretical analysis and simulations. Experimental results for a scale model of the candidate system are presented, which agree with the main conclusions of this paper. [ABSTRACT FROM AUTHOR]