N. Abed

Modeling and Characterization of Induction Motor Internal Faults Using Finite-Element and Discrete Wavelet Transforms

This paper examines the behavior of three phase induction motors with internal fault conditions under sinusoidal supply voltages. Two types of induction machine internal faults are investigated, rotor broken bar, and stator shorted turns 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 obtained by coupling the induction motor transient FE model and external electric circuit. Such a model would allow 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 of the nonstationary current signals for normal and faulty operating conditions.This paper examines the behavior of three phase induction motors with internal fault conditions under sinusoidal and nonsinusoidal supply. This includes rotor broken bar,and stator faults. The terminal behavior of the induction motor was investigated by coupling the induction motor FE model and external circuit. Discrete wavelet transform (DWT)was then used to study the harmonic behavior of the stator currents.

Internal Short Circuit Fault Diagnosis for PM Machines Using FE-Based Phase Variable Model and Wavelets Analysis

This paper presents a procedure using the finite-element (FE)-based phase variable model combined with wavelet analysis to facilitate the fault diagnostic study for permanent magnet machines with internal short circuit faults. Our efforts are dedicated to the aspects of fault modeling and fault extraction. The FE-based phase variable model is developed to describe the PM machine with internal short circuit faults. This model is built with the parameters [inductances and back Electromotive Force (EMF)] obtained from FE computations of the machine with the same type of fault. The developed model has two features. It includes the detailed information of the fault including the location of the shorted turns and the number of turns involved. It keeps the accuracy of the FE model by taking only a fraction of time needed by FE operation. This is particularly desired for diagnosing faults in machines connected to a control circuit. The wavelet transform is used to perform machine current/voltage signature analysis. Excellent results were obtained providing information that would not be otherwise available except by measurement

Investigation of the harmonic behavior of three phase transformer under nonsinusoidal operation using finite element and wavelet packets

This paper investigates the harmonic behavior of three phase power transformers under nonsinusoidal operations. The terminal behavior of the transformer was obtained by coupling the transformer transient finite-element (FE) model and external electric circuits. Such a technique would allow the physical representation of the nonlinear magnetization behavior of the transformer as well as the strong frequency dependence of the transformer parameters. The harmonic behavior of the transformer currents and the dc load current were analyzed using wavelet packet transform algorithm (WPT). The key findings are, uniform frequency bands resulting from WPT decomposition process of the current waveforms can be used for identification of harmonic components. The flattened input voltage distorted by 3rd harmonic component has the highest impact on the dc load current harmonics (with respect to the sinusoidal case). The peaking input voltage distorted by the 5th harmonic component has the highest impact on the transformer secondary current and the magnetizing current harmonics

Modeling and Characterization of Transformers Internal Faults Using Finite Element and Discrete Wavelet Transforms

This paper investigates the behavior of three phase transformers with internal faults under sinusoidal and nonsinusoidal operating conditions. The terminal behavior of the transformer was investigated by coupling the finite element transformers physical model with external electric circuit equations. Two types of internal faults were modeled turn-to-ground faults, and turn-to-turn faults with and without arcing. A discrete wavelet transforms (DWT) procedure was then used to extract the feature of the transformer fault currents. The key advantages of the DWT are its ability to provide a local representation of the current signal for normal and faulty modes, as well as its applicability to handle nonstationary fault signals. This characterization gives us an efficient way to design and evaluate detection algorithms for transformers internal faults and the system they operate in

High frequency PM synchronous motor model determined by FE analysis

A high frequency phase variable model for PM synchronous motor is proposed. It is composed of a low frequency phase variable model with a high frequency winding branch connected in parallel. The winding branch considers the high frequency effects on the machine winding parameters namely resistance, inductance and capacitance. The resistance and inductance of each individual winding turn were calculated by time harmonic FE analysis. The self capacitance of each turn and the mutual capacitances between turns were evaluated by electrostatic FE analysis. Using these circuit parameters, a distributed-parameter winding circuit is formed. The Kron reduction technique is applied to the distributed-parameter winding circuit to obtain a lumped high frequency branch. The implementation is performed on a 2-hp PM synchronous motor and the simulation results show the validity of the proposed model. The originality of this work is that it provides a numerical tool for examining the machine design instead of experiments

Real-Time Simulations of Electrical Machine Drives with Hardware-in-the-Loop

This paper presents a fully digital, real-time hardware-in-the-loop (HIL) simulator on PC-cluster, of electric systems and drives for research and education purpose. This simulator was developed with the aim of meeting the transient simulation needs of electromechanical drives and electric systems while solving the limitations of traditional realtime simulators. This simulator has two main subsystems software and hardware subsystem. The two subsystems were coordinated to achieve the real time simulation. The software subsystem includes Matlab toolbox and a C++ compiler. The hardware subsystem includes FPGA data acquisition card, the control board, the sensors, and the desired motor to be controlled. The use of a real-time simulator to achieve hardware- in-the-Loop (HIL) simulation allows rapid prototyping, motors testing, mechanical load emulation, and control strategies evaluation. . Several simulations with different motors were conducted using this system. The simulation results are outlined and discussed.

Finite-element-based nonlinear physical model of iron-core transformers for dynamic simulations

A finite-element (FE)-based transformer physical phase variable model is proposed. In this model, the effects of nonlinear magnetization on inductances are included by considering the inductance variations with the amplitude of the ac flux as well as its phase angle during a complete ac cycle. Such a consideration is represented by 2-D inductance tables. The magnetizing currents at various magnetization levels are used to calculate the inductances then build the table. The magnetizing currents are determined using circuit-coupled FE analysis of the transformer with sinusoidal voltage supplies. The structure of the inductance table is given and the procedure of inductance table lookup during dynamic simulation is provided. Simulink implementation of the FE-based transformer phase variable model is performed. The validity of the presented technique is verified through comparing the magnetizing current waveforms obtained from the FE-based phase variable model and those from an FE model. The significance of the proposed FE-based phase variable model is in its accuracy and its applicability for dynamic simulation of interconnected components in a power system

Study of High Frequency Model of Permanent Magnet Motor

High frequency model of permanent magnet synchronous motor is developed considering all the turns in the winding. Finite element analysis is used for accurate determination of winding parameters such as resistance, inductance and capacitance at high frequency of operation. From these calculated parameters lumped model is built for high frequency winding branch. Matrix reduction technique is applied to reduce the order of model. This lumped parameter model for high frequency branch is connected in parallel with low frequency phase variable model to form high frequency phase variable motor model. This model is then used in the simulation of integrated motor drive consisting of inverter, cable and motor to predict the overvoltage phenomena at the terminal of motor and internal voltage transient response. Also this model is used in speed control application to show its performance behavior

High Frequency Modeling of PM Synchronous Machine for Use in Integrated Motor Drive

In this paper, a high frequency physical phase variable model of electric machines is presented. The proposed model is composed of a low frequency phase variable model and a high frequency winding branch connected in parallel. The high frequency winding branch is used to include the distributed effects appearing at high frequency operation while the low frequency phase variable model captures the low frequency dynamics. The proposed model parameters are obtained from different types of finite element analyses (FEA), including nonlinear transient analysis, magnetodynamic analysis, and electrostatic analysis. This paper includes determination procedure of the distributed parameter model of the motor winding and its lumping technique. A cable model is developed to investigate its effect on the motor terminal overvoltage. Permanent magnet synchronous motor is used as an example. An experimental verification is conducted to verify the proposed model performance. The significance of the developed model is that it can be used to evaluate different machine designs.

Secure Power Grid Infrastructure Simulation-Test System Creation and Telecommunication Network Implementation

This paper presents a hardware test system developed at Florida International University capable of performing the operation of modern power system infrastructure. The purpose of this system is for research and educational applications. We will describe the design and construction of this test system as well as its implementation to simulate distributed control scheme. Some important elements of the system incorporate real life, flexible power system network hardware, data acquisition (DAQ) system and telecommunication industry standard technologies to deal with issues that could trigger cascaded failures. The research effort develops new techniques for local monitoring of a power system. The data obtained are then used to coordinate the distributed control operation of the power system. This technique enables system operators to locally detect and mitigate potential cascading events before spreading to other areas.