Electrical and Computer Engineering Faculty Research and PublicationsCopyright (c) 2016 Marquette University All rights reserved.
http://epublications.marquette.edu/electric_fac
Recent documents in Electrical and Computer Engineering Faculty Research and Publicationsen-usThu, 01 Dec 2016 01:53:49 PST3600Performance Characterization and Torque-Ripple Reduction in Induction Motor Adjustable Speed Drives Using Time-Stepping Coupled Finite Element State Space Techniques
http://epublications.marquette.edu/electric_fac/256
http://epublications.marquette.edu/electric_fac/256Tue, 29 Nov 2016 11:57:25 PST
In this paper, the time-stepping coupled finite element state space (TSCFE-SS) model developed in the first of two companion papers is applied here for the assessment of effects of machine geometry and magnetic circuit design modifications and the effects of pulse-width modulation carrier frequency on the performance characteristics of induction motor drives. Namely, this has been accomplished through analysis of developed torque profile ripples and harmonic spectra of mid-airgap radial flux density waveforms of the case-study motor. Furthermore, consequent effects of design modifications pertaining to, geometry and/or magnetic circuit modifications, and pulse-width modulation carrier frequency on ohmic and iron core losses are investigated. The investigation has been performed on a case study motor which is a Y-connected, single-layer, 3-phase, 2-pole, 1.2-hp, 208 Volts squirrel-cage induction motor with 24 stator slots, and a cage with 34 rotor bars.
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John Fayia Bangura et al.Effects of Broken Bars/End-Ring Connectors and Airgap Eccentricities on Ohmic and Core Losses of Induction Motors in ASDs Using a Coupled Finite Element-State Space Method (conference proceeding)
http://epublications.marquette.edu/electric_fac/255
http://epublications.marquette.edu/electric_fac/255Tue, 29 Nov 2016 11:48:10 PST
In this paper, effects of rotor abnormalities such as broken squirrel-cage bars, broken cage connectors and airgap eccentricity on ohmic and core losses of induction motors are presented. In this investigation, a comprehensive time-stepping coupled finite element-state space (TSCFE-SS) model was fully utilized to compute the time-domain elemental flux density waveforms and various time-domain waveforms of motor winding currents useful for core loss and ohmic loss computations. Such investigation is feasible by use of the TSCFE-SS model due to its intrinsic nature and characteristics. The results obtained from the simulations of an example 1.2-HP induction motor clearly indicate that faults due to broken squirrel-cage bars/end-connectors can increase motor core losses in comparison to the normal case. The results also give the effect of saturation on the core loss distributions within the cross-section of the motor, and indicate the potential for possible excessive loss concentrations and consequent hot spots near zones of bar and connector breakages in the rotor. Effects of PWM inverter operation on motor losses are also studied.
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John Fayia Bangura et al.Improvement of Monitoring and Diagnosis of Broken Bars/End-Ring Connectors and Airgap Eccentricities of Squirrel-Cage Induction Motors in ASDs using a Time-Stepping Coupled finite Element-state Space Technique
http://epublications.marquette.edu/electric_fac/254
http://epublications.marquette.edu/electric_fac/254Tue, 29 Nov 2016 11:39:01 PST
This paper discusses how a time-stepping coupled finite element-state space (TSCFE-SS) modeling technique can be utilized in diagnostic techniques to improve condition monitoring and diagnosis of induction motor rotor abnormalities of broken bars, broken connectors and airgap eccentricities. This investigation shows that application of the TSCFE-SS modeling technique can facilitate monitoring the characteristics of several frequency components as opposed to merely previous monitoring of sideband frequency components associated with the fundamental in motor phase current waveforms. The results presented in this paper clearly illustrate the possible potential use of the modeling technique for improvement of present diagnostic techniques in which diagnosis of broken bars, broken connectors and airgap eccentricities is restricted to identification of the sidebands associated with the first-order (fundamental) component in phase current waveforms. In addition, the results further demonstrate that database generation for various possible faults prior to their occurrences can be readily achieved using this modeling technique.
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John Fayia Bangura et al.Prediction of Performance Characteristics of a Universal Motor Using Parametric Finite Element Analysis
http://epublications.marquette.edu/electric_fac/253
http://epublications.marquette.edu/electric_fac/253Tue, 29 Nov 2016 10:44:43 PST
A procedure is derived that uses finite element analysis to predict the performance characteristics of a typical universal (AC series) motor. A number of different finite element analyses are made with parametric variations of current and rotor position. Then the AC voltage waveform is applied and the resulting performance is computed using a time-stepping algorithm. The computed torque-speed, current-speed, and power-speed curves are shown to agree closely with the measured curves.
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R. N. Ebben et al.Diagnostics of Bar and End-Ring Connector Breakage Faults in Polyphase Induction Motors Through a Novel Dual Track of Time-Series Data Mining and Time-Stepping Coupled FE-state Space Modeling (conference proceeding)
http://epublications.marquette.edu/electric_fac/252
http://epublications.marquette.edu/electric_fac/252Tue, 29 Nov 2016 10:33:45 PST
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 3, 6, and 9 broken bar and broken end ring connectors in a 208-volt, 60-Hz, 4-pole, 1.2-hp, squirrel cage 3-phase induction motor.
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Richard James Povinelli et al.Diagnostics of Eccentricities and Bar/End-ring Connector Breakages in Polyphase Induction Motors through a Combination of Time-Series Data Mining and Time-Stepping Coupled FE-state Space Techniques (conference proceeding)
http://epublications.marquette.edu/electric_fac/251
http://epublications.marquette.edu/electric_fac/251Tue, 29 Nov 2016 10:27:09 PST
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. The dual-track of generating fault data and mining fault signatures was tested here on dynamic and static eccentricities of 10% and 30% percent of airgap height as well as cases of 1, 3, 6, and 9 broken bars and 3, 6, and 9 broken end-ring connectors. These cases were studied for proof-of-principle in a 208-volt, 60-Hz, 4-pole, 1.2-hp, squirrel cage 3-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 faults.
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John Fayia Bangura et al.Effects of Inductance Nonlinearities in a Transformer-Rectifier DC Motor Drive System on the AC Side Harmonic Distortion using a Time-stepping Coupled Finite Element-Circuit Technique
http://epublications.marquette.edu/electric_fac/250
http://epublications.marquette.edu/electric_fac/250Tue, 29 Nov 2016 07:41:33 PST
The effects of the periodic nature of changes in the magnetic saturation in cores of transformers connected to rectifiers feeding DC motor type loads on performance of the AC side of the system are investigated. Performance issues pertaining to the AC side include harmonic contents of the AC current waveform and total harmonic distortion and their relationship to magnetic saturation effects in transformer cores, whose windings are connected to these rectifiers. The findings were obtained using the rigorous approach of time stepping coupled finite element-state space (TSCFE-SS) modeling and simulation technique, which couples the time-varying magnetic saturation conditions within cores of transformers to their external circuits. The results include TSCFE-SS simulation of the transformer-rectifier-DC-motor load and comparison to laboratory test results on a case study system. The system comprises a 1.5 kVA, 120/277 Volts transformer feeding a full-wave single-phase rectifier bridge which is supplying a 240 V, 7.75 A, 2-pole, separately excited DC motor. The simulation and test data confirm and quantify the significant impact of transformer time-variant core saturation on system currents and harmonic distortion.
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Behrooz Mirafzal et al.A Study of the Effects of Machine Winding Space Harmonics and Advanced Phase Current Switching on Torque and Performance Quality in Brushless DC Motors Using PSpice Modeling
http://epublications.marquette.edu/electric_fac/249
http://epublications.marquette.edu/electric_fac/249Tue, 29 Nov 2016 07:37:09 PST
The effects of space harmonics arising from the topological geometries of the magnetic circuits and winding layouts of permanent magnet brushless dc motors (BDCMs) on their performance are studied here. This includes the synergisms between the space harmonies and the time harmonics generated by the BDCM controller switching. This was accomplished through the development of a PSpice-based model that is presented here. This model fully includes the impact of the space harmonics through the profile variations of all the motor winding's self and mutual inductances with the rotor angular position. These inductances are introduced to the model in a Fourier series form. The simulations, which include all the controller (drive) circuit electronic switching effects reveal the impact of these time and space harmonic synergisms on time-domain motor torque profiles, torque-speed characteristics, line-to-line voltage waveforms, current waveforms, and other performance aspects of the motor and drive. Comparison between simulations, with and without the effects of space harmonics, and test results are presented. In the paper, two 1.2-hp and 15-hp case studies of BDCMs are investigated.
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Chia-Chou Yeh et al.A Nonlinear Controller for Current Source Inverter Induction Motor Drive Systems
http://epublications.marquette.edu/electric_fac/248
http://epublications.marquette.edu/electric_fac/248Tue, 29 Nov 2016 07:32:57 PST
A new approach is presented for the speed control of PWM current source inverter-induction motor (CSI-IM) drive systems. This approach is conceptually based on the well-known feedback linearization technique in nonlinear control theory. Here, the commanded DC link current is generated as a specific nonlinear function of speed in the control algorithm so that the torque-speed characteristic of the CSI-IM system is forced to emulate the torque-speed characteristic of a separately excited DC motor. This is augmented by a feedback controller that slides the torque-speed characteristic along the speed axis in the torque-speed plain, in order to adjust the operating point to any desired value of speed. Meanwhile, it is shown that the proposed controller is highly robust in the presence of external disturbances.
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Behrooz Mirafzal et al.Effects of Load on Diagnosing Broken Bar Faults in Induction Motors Using the Pendulous Oscillation of the Rotor Magnetic Field Orientation
http://epublications.marquette.edu/electric_fac/247
http://epublications.marquette.edu/electric_fac/247Tue, 29 Nov 2016 07:27:56 PST
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. Moreover, the effects of load level on the low side band component of the stator current spectrum 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 that the pendulous oscillation signature can be used for a wide range of motor operating conditions.
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Behrooz Mirafzal et al.Soft Started Induction Motor Modeling and Heating Issues for Different Starting Profiles Using a Flux Linkage ABC-Frame of Reference
http://epublications.marquette.edu/electric_fac/246
http://epublications.marquette.edu/electric_fac/246Tue, 29 Nov 2016 07:22:49 PST
In order to mitigate adverse effects of starting torque transients and high inrush currents in induction motors, a popular method is to use electronically controlled soft starting voltages utilizing series connected silicon controlled rectifiers (SCRs). Investigation of semi-optimum soft starting voltage profiles was implemented using a flux linkage ABC-frame of reference model of a soft started three-phase induction motor. A state-space model of the soft starter thyristor switching sequence for the motor and load was developed and implemented in a time-domain simulation to examine winding heating and shaft stress issues for different starting profiles. Simulation results of line starts and soft starts were compared with measured data through which validation of the model was established. In this paper, different induction machine soft start profiles are shown and comparisons of starting times, torque profiles, and heating losses are made. Discussion of these results and conclusions as to the near-optimum types of profiles are delineated based on peak torque, starting times, and winding heating criteria.
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M. G. Solveson et al.Analysis of Stator Winding Inter-Turn Short-Circuit Faults in Induction Machines for Identification of the Faulty Phase
http://epublications.marquette.edu/electric_fac/245
http://epublications.marquette.edu/electric_fac/245Tue, 29 Nov 2016 07:17:12 PST
The main objective of this paper is to develop and experimentally verify a method of identifying the faulty phase in a three-phase armature of an induction motor with concentric coil construction, when such an armature suffers from an inter-turn within one of its phases. This work leads to a new technique for identifying the faulty phase in concentric wound machines and estimating the associated fault severity without any requirement for additional sensors, wiring constrains, or knowledge of any other details of the machine design. The technique has been verified through several experimental test results
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Ahmed Mohamed Sayed Ahmed et al.Application of Wide Bandgap Devices in Renewable Energy Systems – Benefits and Challenges
http://epublications.marquette.edu/electric_fac/244
http://epublications.marquette.edu/electric_fac/244Tue, 29 Nov 2016 07:07:01 PST
The rapid development of renewable energy systems (RES), especially photovoltaic (PV) energy and wind energy, poses increasing requirements for highpower, low-loss, fast-switching, and reliable semiconductor devices to improve system power capacity, efficiency, power density and reliability. The recent commercialization of wide bandgap (WBG) devices, specifically Silicon Carbide (SiC) and Gallium Nitride (GaN) devices, provides very promising opportunities for meeting such requirements with their attractive features of high voltage blocking capability, ultra-low switching losses, fast switching speed, and high allowable operating temperatures. This paper analyzed the performance benefits and application challenges of using SiC or GaN devices in both PV and wind energy conversion systems. Solutions to these challenges of using WBG devices in various RES were reviewed and proposed, and the benefits of using such emerging devices were confirmed in simulation based on a 250 kW commercial-scale PV inverter and a 250 kW doubly fed induction generator wind turbine system.
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Jiangbiao He et al.Design Optimization of IPM Machines for Efficient Operation in Extended Speed Range
http://epublications.marquette.edu/electric_fac/243
http://epublications.marquette.edu/electric_fac/243Tue, 29 Nov 2016 06:54:52 PST
Practical considerations in the design of Interior Permanent Magnet (IPM) machines are examined to identify the key objectives for large-scale design optimization of such machines over an extended speed range. The goal of the optimization is to ensure efficient operation over the entire operating range under various performance and operational constraints. First, this paper illustrates that when the non-linear and lossy nature of the machine is considered from the efficiency standpoint, congruity of the characteristic versus the rated current cannot be the ideal criterion for constant power operation. Second, a new design optimization algorithm for constant power operation is developed which pursues efficient and reliable performance in the extended speed range under the rated current and maximum voltage constraints. To include the full non-linear nature of the machine and to address the effects of copper and iron losses on the motor behavior, this study is centered on finite element (FE) method for analysis and consequently optimization of a 50 hp, 48-slot, 8-pole IPM with single-layer v-type magnets which is used in the 2004 Toyota Prius. The results can be generalized to other PM motor configurations with sinusoidal back-emf waveforms.
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Alireza Fatemi et al.Fault Tolerant Operations in Adjustable-Speed Drives and Soft Starters for Induction Motors
http://epublications.marquette.edu/electric_fac/242
http://epublications.marquette.edu/electric_fac/242Tue, 29 Nov 2016 06:14:33 PST
Fault tolerant operations of soft starters and adjustable-speed drives (ASDs) when experiencing power switch open-circuit or short-circuit faults are presented in this paper. The present low-cost fault mitigation solutions can be retrofitted into the existing off-the-shelf soft starters and ASDs with only minimum hardware modifications. The fault tolerant soft starters are capable of operating in a two-phase mode under the condition of thyristor/SCR open-circuit or short-circuit switch-fault in any one of the phases using a novel resilient closed-loop control scheme. The performance resulted from the present soft starter fault tolerant control has demonstrated reduced starting motor torque transient and inrush current magnitude. As for the ASDs, a low-cost fault mitigation strategy for low-speed applications such as "self-healing/limp-home" needs for vehicles and propulsion systems, with capabilities for mitigating transistor open-circuit and short-circuit switch-faults was developed. The present fault tolerant drive topology requires only minimum hardware modifications to the conventional off-the-shelf six-switch three-phase drive, with only the addition of electronic components such as triacs and fast-acting fuses. In addition, the present approach offers the potential of mitigating not only transistor switch-faults but also drive related faults such as rectifier diode short-circuit fault or dc link capacitor fault. Given in this paper is a complete set of simulation results that demonstrate the soundness and effectiveness of the present fault tolerant approaches.
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Chia-Chou Yeh et al.