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Dynamic rotor faults of induction motors, mainly broken or cracked rotor bars and dynamic rotor eccentricity, cause stator currents modulation. The detailed motor current analysis revealed meaningful phase modulation and its relation to amplitude modulation at increasing motor load and inertia load It is shown, that by increasing motor load mainly phase modulation increases and by increasing inertia...
This contribution presents a Modelica library for the simulation of electrical asymmetries in multiphase machines -the ExtendedMachines library. Simulation models of squirrel cage and slip ring induction machines, permanent magnet and electrical excited synchronous machines and reluctance machines are introduced. The object oriented model approach, in particular with respect to various models abstractions...
The growing application of asynchronous motors in industrial processes that require high security and reliability levels has led to the development of multiple methods for early fault detection. The design and verification of these methods imply the use of complex mathematical models that allow the study of the influence produced by the machine operating conditions over the diagnosis procedure. The...
A diagnostic method for armatures of commutator motors using the frequency response analysis method (FRA) is presented in this paper. The proposed method can, beside the detection of the fault itself, recognize and categorize the fault types. In a first step, the magnetic and capacitive couplings of the armature single components are analyzed. Thereafter, the position-dependent impedance curves of...
A 3D model reflecting entire internal structure of the asynchronous machine using finite elements method, has been presented here. Nodal finite elements have been used to approximate scalar potential and edge finite elements to approximate vector magnetic potential. This model includes both the skew of the rotor bars as well cross current flowing through the rotor iron laminates. The three-phase stator...
Mathematical modeling is a basic way to simulate electric machines under various faulty conditions because it is to dangerous and/or to expensive to recognize properties of faulty machines by tests in the field or even on specialized test beds. Nowadays, signature analysis of measurable currents of machine windings is the most permissible way to characterize and to compare various faulty conditions...
A method is here presented that allows the diagnosis of broken rotor bars in time varying operations with simple post processing of input currents. Extensive simulations are presented to validate the proposed approach for open loop and closed loop induction machines. A diagnostic index is presented also, that is quite robust versus load and inertia variations.
The aim of this paper is to analyze experimentally the stray flux spectrum of a three phase induction machine in order to show how it is influenced by the mechanical behavior induced by bearings, gearbox and the inherent eccentricity of the rotor. For this analysis, the influence of the mechanical behavior on the stator current spectrum is firstly verified and then analyzed in the electromotive force...
The mathematical model of dc motor was created. In model the commutator is approximated by circuit with variable parameters. Extremely different values are assigned to circuit parameters depending on the angular position of the rotor. Model equations were solved using implicit integration method. Commutation processes of dc motor were investigated with the aid of this model. Presented model can be...
This paper proposes a comparison of several circuit models of induction motors with broken bars in terms of representation of the phenomena, identifiability of its parameters as well as computing time. Such a comparison is rare as many papers focus on the presentation of new models. The three models studied in this paper are based on electrical circuit equations obtained using a common set of hypotheses...
The aim of the paper is to show several case histories regarding the diagnosis of rotor asymmetries and other faults in large induction motors. These are motors under real operation in power generating installations. Two different approaches are used for the diagnosis of the machine condition. Both of them are based on the study of the startup transient of the machine and the extraction of characteristic...
Fault diagnosis of electrical machines has primarily been focused on steady state operation of the machine due to the limitations in signal processing techniques. However, the advancement in this area has led to the development of a new class of algorithms which are time-frequency based signal processing techniques. In this paper we explore the concept of identifying faults by analyzing the transient...
In this paper, we propose to perform early fault diagnosis using high-resolution spectral analysis of the stator current to detect bearing faults in electrical induction machine. While most research works focus on mechanical vibration analysis, the originality of our work relies on the use of high-resolution methods to detect modulations in the stator current. We present the results obtained for real...
Current-based monitoring can offer significant economic savings and implementation advantages over traditional vibration monitoring for bearing fault detection. A key issue in current-based bearing fault detection is to extract bearing fault signature from motor stator current. In this paper bearing fault signature in motor stator current is detected by estimating and removing non-bearing fault components...
Compared to conventional monitoring techniques such as vibration monitoring or temperature monitoring, stator current-based monitoring offers significant economic savings and implementation advantages. Consequently, stator current-based bearing fault detection has received more and more attention in research. Further more, according to a recent study, bearing faults can be categorized into two classes:...
Planning for an upcoming refueling shutdown at Limerick Nuclear Power Station, sixteen vane axial fans were analyzed to determine which ones need maintenance. Vibration and torque signature technologies were employed. Vibration technology is the standard bearing diagnostic approach; however, the need of physical proximity limits the usability to low radiation areas. Lacking this drawback, torque signature...
Bearing faults account for approximately half of all electric machine failures. Bearing condition monitoring is of practical importance. In this paper, up to seven different bearing condition monitoring methods in terms of the measuring medium are reviewed, with an emphasis on their implementation considerations. The major advantages and disadvantages of those methods are also summarized. This paper...
PD patterns indicate faults in the mica insulation of the stator windings of high voltage synchronous turbo generators. The common used method for PD measurement on electrical machines is the phase resolved partial discharge pattern (PRPDP) Method. Usually these patterns can only be interpreted by experienced test engineers. A computer program has been developed which is capable of interpreting these...
Measurement investigations have been carried out for commutator DC motor with internal asymmetries. Construction of considered motor enables to realize the breaking of one rotor coil and shorting of two groups of rotor coils. Each group contains three rotor coils. The basis of study were signals: current and voltage of field winding, current and voltage of armature winding and velocity of the rotor...
This paper presents an automated technique to verify the NEMA standard MG-1 voltage unbalance derating graph using temperature sensors embedded in a 5 hp motor. This two step process initially identifies the reference coil temperature. Once the reference temperature is found, the system automatically regulates the load to maintain the reference temperature at the single hottest coil for a wide range...
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