S. Ganu

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.

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

FE-Circuit Coupled Model of Electric Machines for Simulation and Evaluation of EMI Issues in Motor Drives

A new FE-circuit coupled model is proposed to simulate the electromagnetic field interference (EMI) caused by terminal overvoltage and ground current of electric machines connected to driving circuits. The high frequency effects due to the PWM drive were considered in the transient FE-circuit coupled model of the motor using a two-step procedure. First, the resistance in each individual winding turn of a coil is evaluated by time harmonic high frequency FE analysis considering skin and proximity effects. The capacitances of the coil were calculated by an electrostatic FE analysis to form a distributed parameter model of the coil in each conducting region. Second, a lumped parameter model for the coil was obtained through a matrix reduction technique. The lumped models of the different coils were connected in series to form a per phase winding model. The FE-circuit coupled model of the motor is tested in a motor drive to evaluate the terminal over voltages and ground currents. The numerical results were successfully verified by the corresponding laboratory test measurements. The proposed model can be used as a novel computational prototyping tool which would allow the development to design and final product stages to be completed without the need for repeated build and test procedures in an industrial environment.

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.

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.

Innovations in teaching energy systems utilizing an integrated simulation environment

The purpose of this presentation is to show the latest efforts by the authors in the development of integrated drive simulation environment. Furthermore, we present the utilization of these research developments into the classroom and how it can be integrated into lectures. We want to help students acquire the knowledge related to actual operations of integrated power systems, for example, the physical behavior of various electrical components, interactions of the individual components with each other during dynamic operations. We could also show component reactions to changes in system parameters or operation conditions as well as study the effects of design changes. The development of physical component modeling and the integrated coupling of these realistic physical modeling with the over all system have led to the creation of realistic practical system that is capable of simulating dynamic operations. This environment also includes hardware-in-the-loop ability along with distributed simulation in order to achieve research innovations in addition to the associated education benefits.

Effect of change in pole shape design on harmonic contents of PM synchronous motor air gap flux density waveform

This paper utilizes the wavelet packet transform to study the effects of change in the shape of the magnetic pole on the harmonic behavior of air gap flux density waveform. A surface mounted PM motor is used as an example. The original design contains 6 PM poles and 36 stator slots. The rotor and the stator winding are redesigned to have 4, 8, and 12 poles. The air gap flux density waveform is obtained from the finite element solutions. The results have been compared with different pole structure design. It has been found that there is not much difference in the harmonic content due to change in PM pole structure on the air gap flux density waveform.

FEM analysis and testing of magnetostrictive effects in electrical samples for machinery applications

This paper investigates the numerical results relating to magnetostrictive effects in an electrical steel sample. This is based upon the magneto-mechanical coupling. The magnetic field causes elastic deformation and mechanical stress changes the magnetization curve and the hysteresis loop. As the applied stress is increased, material permeability increases. Pre-stressed magnetic material may show the promise of increased power density in the manufacturing of electric machinery.

Harmonic analysis of induction motor flux density waveform using wavelets in speed control application

The lack of a numerical model in the literature for harmonic analysis of the air gap flux density waveform in an induction motor speed control application, by changing pole numbers, inspires this study. One of the methods for speed control of an induction motor is to change the number of poles of the stator winding. The change in the pole numbers introduces additional harmonics in the air gap flux density waveforms which are harmful to machine performance as well as equipment connected to it. The wavelet packet transform is used to quantify the harmonics in the flux density waveform. The results are useful in the design and development of both motor and drive diagnosis systems. The originality and significance of this research is to enable researchers to choose a proper induction motor in speed control applications by changing pole numbers.