Showing papers on "Induction motor published in 2010"

H-bridge drive circuit for step motor control

Abstract: A drive circuit for step motors with bifilar windings is provided in which both parallel and series winding configurations for the stator coils are selectable by a motor controller based on the motor speed. For low speeds a series configuration is selected, while for higher speeds a parallel configuration is selected. Dynamic torque is optimized by the selection for more efficient motor operation with less drive current.

Low output frequency operation of the Modular Multi-Level Converter

Abstract: Modular Multilevel Converters (MMLC) based on series connected half-bridges achieve high phase voltages, need little or no filters and feature redundancy and modularity. In contrast to the similar series connected H-bridge converters an expensive and lossy transformer is not necessary. The capacitors buffer power fluctuations at fundamental and second harmonic frequency, therefore the capacitor voltage ripple magnitude increases with decreasing phase current frequencies and will become infinite at zero phase current frequency. This is a problem in variable speed drive applications where phase current frequencies from starting from zero are needed. An operating mode for low phase current frequencies which enables MMLCs to magnetize and start induction machines with quadratic torque loads is presented and the achievable torque-speed characteristic is derived. It is also shown that rotor flux optimization also reduces the capacitor voltage ripple at low torque. The method has successfully been tested in an experimental converter.

Stator-Current-Based MRAS Estimator for a Wide Range Speed-Sensorless Induction-Motor Drive

Abstract: This paper deals with an analysis of the vector-controlled induction-motor (IM) drive with a novel model reference adaptive system (MRAS)-type rotor speed estimator. A stability-analysis method of this novel MRAS estimator is shown. The influence of equivalent-circuit parameter changes of the IM on the pole placement of the estimator transfer function and the stability of the whole drive system are analyzed and tested. The influence of the adaptation-algorithm coefficients of the MRAS-estimator scheme is also tested. The allowable range of motor-parameter changes is determined, which guarantees the stable operation of the sensorless field-oriented IM drive with this speed and flux estimator. Dynamical performances of the vector-control system with the current-type MRAS estimator are tested in a laboratory setup.

Direct Active and Reactive Power Regulation of DFIG Using Sliding-Mode Control Approach

Abstract: This paper presents a new direct active and reactive power control (DPC) of grid-connected doubly fed induction generator (DFIG)-based wind turbine systems. The proposed DPC strategy employs a nonlinear sliding-mode control scheme to directly calculate the required rotor control voltage so as to eliminate the instantaneous errors of active and reactive powers without involving any synchronous coordinate transformations. Thus, no extra current control loops are required, thereby simplifying the system design and enhancing the transient performance. Constant converter switching frequency is achieved by using space vector modulation, which eases the designs of the power converter and the ac harmonic filter. Simulation results on a 2-MW grid-connected DFIG system are provided and compared with those of classic voltage-oriented vector control (VC) and conventional lookup table (LUT) DPC. The proposed DPC provides enhanced transient performance similar to the LUT DPC and keeps the steady-state harmonic spectra at the same level as the VC strategy.

Stator Current and Motor Efficiency as Indicators for Different Types of Bearing Faults in Induction Motors

Abstract: This paper proposes a new approach to use stator current and efficiency of induction motors as indicators of rolling-bearing faults. After a presentation of the state of the art about condition monitoring of vibration and motor current for the diagnostics of bearings, this paper illustrates the experimental results on four different types of bearing defects: crack in the outer race, hole in the outer race, deformation of the seal, and corrosion. The first and third faults have not been previously considered in the literature, with the latter being analyzed in other research works, even if obtained in a different way. Another novelty introduced by this paper is the analysis of the decrease in efficiency of the motor with a double purpose: as alarm of incipient faults and as evaluation of the extent of energy waste resulting from the lasting of the fault condition before the breakdown of the machine.

Predictive Direct Torque Control for Flux and Torque Ripple Reduction

Abstract: In this paper, a prediction scheme is presented to diminish both the torque and flux ripples in a direct torque control (DTC) induction motor drive. In a discrete implementation of the classical DTC scheme, the time delay associated with data processing results in additional torque and flux ripples. This part of the ripples can amount to a significant fraction of the overall ripple if the hysteresis bands are comparable to the maximum torque and flux variations in one sampling interval. This paper presents a prediction scheme with low computational complexity and low parameter sensitivity, both comparable to the standard DTC scheme. The prediction scheme can easily be extended to compensate for multiple time delays when the sampling frequency is raised but the computation time remains unchanged. Experimental results show the diminishing effect of the prediction scheme on the torque and flux ripples.

Global Minimum Torque Ripple Design for Direct Torque Control of Induction Motor Drives

Abstract: This paper proposes a simple but effective method to reduce the torque ripple for direct torque control (DTC) of induction motor drives. The proposed DTC provides a global minimum torque ripple, which satisfies the root-mean-square (rms) criteria of torque ripple. Such a global minimum torque ripple DTC has not been derived before. The proposed global minimum torque ripple DTC is a two-step design. The first step drives the torque error to zero at the end of the control period. Then, the second step reduces the torque bias and rms ripple by modifying the asymmetry switching patterns of the applied voltage vectors of the first step into symmetry ones. Theoretical analysis is provided to show that the torque ripple of the proposed DTC is a global minimum rms ripple. Furthermore, to verify the effectiveness of this study, a DSP-based experimental induction motor DTC drive system is built. Simulation and experimental results verify that the torque ripple performance has been improved.

MRAS Sensorless Vector Control of an Induction Motor Using New Sliding-Mode and Fuzzy-Logic Adaptation Mechanisms

Abstract: In this paper, two novel adaptation schemes are proposed to replace the classical PI controller used in model reference adaptive speed-estimation schemes that are based on rotor flux. The first proposed adaptation scheme is based on sliding-mode theory. A new speed-estimation adaptation law is derived using Lyapunov theory to ensure estimation stability, as well as fast error dynamics. The other adaptation mechanism is based on fuzzy-logic strategy. A detailed experimental comparison between the new and conventional schemes is carried out in both open- and closed-loop sensorless modes of operation when a vector control drive is working at very low speed. Superior performance has been obtained using the new sliding-mode and fuzzy-logic adaptation mechanisms in both modes of operations.

Hybrid Cascaded H-Bridge Multilevel-Inverter Induction-Motor-Drive Direct Torque Control for Automotive Applications

Abstract: This paper presents a hybrid cascaded H-bridge multilevel motor drive direct torque control (DTC) scheme for electric vehicles (EVs) or hybrid EVs. The control method is based on DTC operating principles. The stator voltage vector reference is computed from the stator flux and torque errors imposed by the flux and torque controllers. This voltage reference is then generated using a hybrid cascaded H-bridge multilevel inverter, where each phase of the inverter can be implemented using a dc source, which would be available from fuel cells, batteries, or ultracapacitors. This inverter provides nearly sinusoidal voltages with very low distortion, even without filtering, using fewer switching devices. In addition, the multilevel inverter can generate a high and fixed switching frequency output voltage with fewer switching losses, since only the small power cells of the inverter operate at a high switching rate. Therefore, a high performance and also efficient torque and flux controllers are obtained, enabling a DTC solution for multilevel-inverter-powered motor drives.

Fuzzy Logic and Sliding-Mode Controls Applied to Six-Phase Induction Machine With Open Phases

Abstract: The faulted mode of a six-phase induction machine (6PIM) denotes that the motor is working with one or more missing phases. This situation leads to torque oscillations and poor tracking behavior. Therefore, the design of a suitable robust control is a challenging task. In this way, this paper presents the application of fuzzy logic and sliding mode controls in order to obtain a high-accuracy positioning of a 6PIM rotor in both healthy and faulted modes. The two control strategies are completely different from a theoretical point of view, but the final objectives are to remove the drawbacks of the specific fault on interest. The experimental results are obtained on a dedicated setup based on a 6PIM coupled with a variable mechanical load and for which up to three phases can be removed.

Adaptive Sliding-Mode Neuro-Fuzzy Control of the Two-Mass Induction Motor Drive Without Mechanical Sensors

Abstract: In this paper, the concept of a model reference adaptive control of a sensorless induction motor (IM) drive with elastic joint is proposed. An adaptive speed controller uses fuzzy neural network equipped with an additional option for online tuning of its chosen parameters. A sliding-mode neuro-fuzzy controller is used as the speed controller, whose connective weights are trained online according to the error between the estimated motor speed and the speed given by the reference model. The speed of the vector-controlled IM is estimated using the MRASCC rotor speed and a flux estimator. Such a control structure is proposed to damp torsional vibrations in a two-mass system in an effective way. It is shown that torsional oscillations can be successfully suppressed in the proposed control structure, using only one basic feedback from the motor speed given by the proposed speed estimator. Simulation results are verified by experimental tests over a wide range of motor speed and drive parameter changes.

Induction Motor Control Design

Abstract: Nonlinear and Adaptive Control Design for Induction Motors is a unified exposition of the most important steps and concerns in the design of estimation and control algorithms for induction motors. A single notation and modern nonlinear control terminology is used to make the book accessible to readers who are not experts in electric motors at the same time as giving a more theoretical control viewpoint to those who are. In order to increase readability, the book concentrates on the induction motor, eschewing the much more complex and less-well-understood control of asynchronous motors. The concepts of stability and nonlinear control theory are presented in appendices. Important features of the book include: i) thorough coverage of speed sensorless control, important for applications; ii) a wide-ranging discussion of nonlinear adaptive controls containing parameter estimation algorithms; iii) coverage of the design of adaptive observers and parameter estimators which can complement state feedback design techniques; iv) comparative simulations of different control algorithms on the same motor to clarify the advantages and drawbacks of each. The content is organized in a pedagogical, progressive exposition starting from basic assumptions, structural properties, modelling, state feedback control and estimation algorithms, and moving on to more complex output feedback control algorithms and modelling for speed sensorless control. Adaptive output feedback controls are based on stator current measurements, both alone and in connection with rotor speed. The induction motor exhibits many typical and unavoidable nonlinear features and so the material presented in this volume will be of value to engineers engaged in the control of electric motors and to a broader audience interested in nonlinear control design.

A Wound-Field Three-Phase Flux-Switching Synchronous Motor With All Excitation Sources on the Stator

Abstract: A three-phase, segmental-rotor, flux-switching synchronous motor is presented for the first time, with both field and armature windings placed on the stator. Mutual coupling of the circuits is through segments whose motion causes switching of flux in the armature circuit. The magnetic geometry is substantially different to that of other flux-switching machines (FSMs), and may offer advantages in terms of torque density and controllability. This paper describes the principles and the evaluation of a three-phase design, based on a 12-tooth stator with an eight-segment rotor, before introducing a prototype machine and test results. The prototype has been found to have torque density and profile comparable to that of a switched reluctance motor (SRM) of the same size.

Design Optimization of Transverse Flux Linear Motor for Weight Reduction and Performance Improvement Using Response Surface Methodology and Genetic Algorithms

Abstract: Permanent magnet (PM) type transverse flux linear motors (TFLMs) are electromagnetic devices, which can develop directly powerful linear motion. These motors have been developed to apply to high power system, such as railway traction, electrodynamics vibrator, free-piston generator, etc. This paper presents an optimum design of a PM-type TFLM to reduce the weight of motor with constraints of thrust and detent force using response surface methodology (RSM) and genetic algorithms (GAs). RSM is well adapted to make analytical model of motor weight with constraints of thrust and detent forces, and enable objective function to be easily created and a great computational time to be saved. Finite element computations have been used for numerical experiments on geometrical design variables in order to determine the coefficients of a second-order analytical model for the RSM. GAs are used as a searching tool for design optimization of TFLM to reduce the weight of motor and improve the motor performance.

AC Motor Control and Electrical Vehicle Applications

Abstract: Preliminaries for Motor Control Basics of DC Machines Types of Controllers Rotating Field Theory Construction of Rotating Field Change of Coordinates Induction Motor Basics IM Operation Principle Leakage Inductance and Circle Diagram Slot Leakage Inductance and Current Displacement IM Speed Control Dynamic Modeling of Induction Motors Voltage Equation IM Dynamic Models Steady State Models Power and Torque Equations Field Oriented Controls of Induction Motors Direct versus Indirect Vector Controls Rotor Field Orientated Scheme Stator Field Oriented Scheme Field Weakening Control Speed Sensorless Control of IMs PI Controller in the Synchronous Frame [5], [6] Permanent Magnet AC Motors PMSM and BLDC Motor PMSM Dynamic Modeling PMSM Torque Equations PMSM Block Diagram and Control PMSM High Speed Operation Machine Sizing Extending Constant Power Speed Range Current Control Methods Properties When psim = LdIs Per Unit Model of the PMSM An EV Motor Example Loss Minimizing Control Motor Losses Loss Minimizing Control for IMs Loss Minimizing Control for IPMSMs Sensorless Control of PMSMs IPMSM Dynamics a Misaligned Frame Sensorless Control for SPMSMs Sensorless Controls for IPMSMs Starting Algorithm by Signal Injection Method High Frequency Signal Injection Methods Pulse Width Modulation and Inverter Switching Functions and Six Step Operation PWM Methods Speed/Position and Current Sensors Vehicle Dynamics Longitudinal Vehicle Dynamics Acceleration Performance and Vehicle Power Driving Cycle Hybrid Electric Vehicles HEV Basics HEV Power Train Configurations Planetary Gear Power Split with Speeder and Torquer Series/Parallel Drive Train Series Drive Train Parallel Drive Train Battery EVs and PHEVs Electric Vehicles Batteries BEV and PHEV BEVs Plug-in Hybrid Electric Vehicles EV Motor Design Issues Types of Synchronous Motors Distributed and Concentrated Windings PM Eddy Current Loss and Demagnetization EV Design Example Index

Synchronous Optimal Pulsewidth Modulation for Low-Switching-Frequency Control of Medium-Voltage Multilevel Inverters

Abstract: This paper presents the mechanism and details of synchronous optimal pulsewidth modulation (PWM) generation for control of medium-voltage induction motor drives using multilevel inverters at low switching frequency. Multilevel inverters allow operation at multiple of dc-link voltage and reduce the total harmonic distortion (THD). Synchronous optimal PWM control permits setting the maximum switching frequency to a low value without compromising THD. Low switching frequency reduces the switching losses of the power semiconductor devices. An optimal control procedure is explained in detail. The performances of three- and five-level inverter topologies are compared. The experimental results of a five-level inverter drive using optimal PWM control are presented.

Detection of Motor Bearing Outer Raceway Defect by Wavelet Packet Transformed Motor Current Signature Analysis

Abstract: Motor current signature analysis (MCSA) is a method of sampling the running current through a data logger at high sampling speed, followed by using mathematical tools such as fast Fourier transform (FFT) to identify relevant motor signature changes in the frequency spectrum for motor fault identification. Although there are numerous types of motor fault, research conducted by Electric Power Research Institute (EPRI) indicated that motor bearing fault accounted for more than 40% of all types of motor fault. The main aim of this paper is to evaluate the use of MCSA for detecting bearing outer raceway defect. Stage-by-stage experimental verification shows that the method of MCSA is effective in detecting bearing fault with the use of wavelet packet transformation (WPT). In addition, a novel linear application of linear regression for wavelet data analysis is applied and presented in this paper.

A Real-Time Thermal Model of a Permanent-Magnet Synchronous Motor

Abstract: This paper presents a real-time thermal model with calculated parameters based on the geometry of the different components of a permanent-magnet synchronous motor. The model in state-space format has been discretized and a model-order reduction has been applied to minimize the complexity. The model has been implemented in a DSP and predicts the temperature of the different parts of the motor accurately in all operating conditions, i.e., steady-state, transient, and stall torque. The results have been compared with real measurements using temperature transducers showing very good performance of the proposed thermal model.

Simulation and comparison of spwm and svpwm control for three phase inverter

Abstract: A voltage source inverter is commonly used to supply a three-phase induction motor with variable frequency and variable voltage for variable speed applications. A suitable pulse width modulation (PWM) technique is employed to obtain the required output voltage in the line side of the inverter. The different methods for PWM generation can be broadly classified into Triangle comparison based PWM (TCPWM) and Space Vector based PWM (SVPWM). In TCPWM methods such as sine-triangle PWM, three phase reference modulating signals are compared against a common triangular carrier to generate the PWM signals for the three phases. In SVPWM methods, a revolving reference voltage vector is provided as voltage reference instead of three phase modulating waves. The magnitude and frequency of the fundamental component in the line side are controlled by the magnitude and frequency, respectively, of the reference vector. The highest possible peak phase fundamental is very less in sine triangle PWM when compared with space vector PWM. Space Vector Modulation (SVM) Technique has become the important PWM technique for three phase Voltage Source Inverters for the control of AC Induction, Brushless DC, Switched Reluctance and Permanent Magnet Synchronous Motors. The study of space vector modulation technique reveals that space vector modulation technique utilizes DC bus voltage more efficiently and generates less harmonic distortion when compared with Sinusoidal PWM (SPWM) technique. In this paper first a model for Space vector PWM is made and simulated using MATLAB/SIMULINK software and its performance is compared with Sinusoidal PWM. The simulation study reveals that Space vector PWM utilizes dc bus voltage more effectively and generates less THD when compared with sine PWM.

Comparison of different motor design drives for hybrid electric vehicles

Abstract: This paper describes an investigation into different motor designs for an application dictated by the performance of an existing hybrid electric vehicle drive (an internal permanent magnet motor) An induction motor and switched reluctance motor are studied Torque over a wide speed range is required (base speed of 1500 rpm and maximum speed of 6000 rpm) and the total torque per volume is used as a key marker indicator The efficiency is studied and efficiency plots are introduced; predicted losses are used to investigate thermal conditions and temperature rise, which affect the machines described in the paper Results indicate that at 1500 rpm very high current density exists in all the machines whilst at 6000 rpm the iron loss dominates The paper illustrates that the permanent magnet motor is not the sole solution to specifying a drive motor for this application

Optimal MLP neural network classifier for fault detection of three phase induction motor

Abstract: Induction motors are critical components in commercially available equipments and industrial processes due to cost effective and robust performance. Under various operating stresses, motors deteriorate their conditions which result into various faults. Early detection and diagnosis of these faults are desirable for online condition assessment, product quality assurance and improved operational efficiency. From the related work reported so far it is observed that researchers used vibration analysis, harmonics present in stator current, chemical analysis, electromagnetic analysis, etc. As these approaches are complex in view of the requirement of precise measurement and mathematical modeling. As compared to analytical methods, AI based schemes are more efficient and accurate. In this paper optimal MLP NN based classifier is proposed for fault detection which is inexpensive, reliable, and noninvasive by employing more readily available information such as stator current. Detailed design procedure for MLP and SOM NN models is given for which simple statistical parameters are used as input feature space and Principal Component Analysis is used for reduction of input dimensionality. Robustness of classifier to noise is verified on unseen data by introducing controlled Gaussian and Uniform noise in input and output.

Estimation of Iron Losses in Induction Motors: Calculation Method, Results, and Analysis

Abstract: This paper intends to develop a more accurate approach for determining the no-load iron losses in pulse width modulation (PWM) inverter fed induction motors. The proposed method is validated by means of a prototype motor with a plastic rotor cage. The iron losses have been computed by the time-stepping finite element method, both with sinusoidal and PWM supply. The iron losses have then been estimated by adding up the contribution generated by orthogonal components of the flux density, as if the iron losses generated by these components were independent phenomena. The rotational hysteresis losses, as well as excess ones, have been calculated applying a correction factor based on experimental data. These factors are a function of the peak flux density and ellipticity of the B vector loci. Experimental validations are provided for several frequency and magnetic saturation values. In addition, this paper demonstrates the necessity to consider the harmonics initial phase in order to increase the accuracy in the iron loss prediction.

Equivalent Circuits for Single-Sided Linear Induction Motors

Abstract: Single-sided linear induction motors (SLIMs) have lately been applied in transportation system traction drives, particularly in the intermediate speed range. This is because they have merits, such as the ability to exert thrust on the secondary without mechanical contact, high acceleration or deceleration, less wheel wear, small turning circle radius, and flexible road line. The theory of operation for these machines can be directly derived from rotary induction motors (RIMs). However, while the cut-open primary magnetic circuit has many inherent characteristics of the RIM equivalent circuits, several issues involving the transversal edge and longitudinal end effects and the half-filled slots at the primary ends need to be investigated. In this paper, a T-model equivalent circuit is proposed which is based on the 1-D magnetic equations of the air gap, where half-filled slots are considered by an equivalent pole number. Among the main five parameters, namely, the primary resistance, primary leakage inductance, mutual inductance, secondary resistance, and secondary inductance, the mutual inductance and the secondary resistance are influenced by the edge and end effects greatly, which can be revised by four relative coefficients, i.e., Kr, Kx, Cr, and Cx. Moreover, two-axis equivalent circuits (dq or αβ) according to the T-model equivalent circuit are obtained using the power conversion rule, which are analogous with those of the RIM in a two-axis coordinate system. The linear induction motor dynamic performance, particularly the mutual inductance and the secondary resistance, can be analyzed by the four coefficients. Experimental verification indicates that both the T-model and the new two-axis circuits are reasonable for describing the steady and dynamic performance of the SLIM. These two models can provide good guidance for the electromagnetic design and control scheme implementation for SLIM applications.

High-Frequency Modeling of the Long-Cable-Fed Induction Motor Drive System Using TLM Approach for Predicting Overvoltage Transients

Abstract: Induction motor drive systems fed with cables are widely used in many industrial applications. Accurate prediction of motor terminal overvoltage, caused by impedance mismatch between the long cable and the motor, plays an important role for motor dielectric insulation and optimal design of dv/dt filters. In this paper, a novel modeling methodology for the investigation of long-cable-fed induction motor drive overvoltage is proposed. An improved high-frequency motor equivalent circuit model is developed to represent the motor high-frequency behavior for the time- and frequency-domain analyses. The motor equivalent circuit parameters for the differential mode (DM) and common mode (CM) are extracted based on the measurements. A high-frequency cable model based on improved high-order multiple-π sections is proposed. The cable model parameters are identified from the DM impedances in open circuit (OC) and short circuit (SC). To obtain a computationally efficient solution that could potentially be integrated with the motor drive controller, the system equations are discretized and solved using transmission-line modeling (TLM) approach. The proposed methodology is verified on an experimental 2.2-kW ABB motor drive benchmark system. The motor overvoltage transients predicted by the proposed model is in excellent agreement with the experimental results and represents a significant improvement compared with the conventional models.

Speed and Load Torque Observer Application in High-Speed Train Electric Drive

Abstract: This paper presents an application of induction motor mechanical speed and load torque observers in high-speed train drives. The observers are applied for a 1.2-MW electric drive with an induction motor. The goal of using such observers is to utilize computed variables for diagnostic purposes of speed sensors and torque transmission system. The concept of diagnostic system is presented in this paper, and proper criteria are proposed. The suggested system is designed to work without a speed sensor in the case of existing sensor faults. Monitored motor load torque is used to limit the maximum motor torque in the case of existing problems in the gearbox. The results of simulation and experimental investigations for a 1.2-MW induction motor drive are presented.

Design Optimization of Short-Stroke Single-Phase Tubular Permanent-Magnet Motor for Refrigeration Applications

Abstract: This paper describes a design methodology to achieve optimal performance for a short-stroke single-phase tubular permanent-magnet motor which drives a reciprocating vapor compressor. The steady-state characteristic of the direct-drive linear-motor compressor system is analyzed, an analytical formula for predicting iron loss is presented, and a motor-design procedure which takes into account the effect of compressor loads under nominal operating condition is formulated. It is shown that the motor efficiency can be optimized with respect to two leading dimensional ratios. Experimental results validate the proposed design methodology.

Novel Direct Torque Control Based on Space Vector Modulation With Adaptive Stator Flux Observer for Induction Motors

Abstract: This paper describes a combination of direct torque control (DTC) and space vector modulation (SVM) for an adjustable speed sensorless induction motor (IM) drive. The motor drive is supplied by a two-level SVPWM inverter. The inverter reference voltage is obtained based on input-output feedback linearization control, using the IM model in the stator D-Q axes reference frame with stator current and flux vectors components as state variables. Moreover, a robust full-order adaptive stator flux observer is designed for a speed sensorless DTC-SVM system and a new speed-adaptive law is given. By designing the observer gain matrix based on state feedback H∞ control theory, the stability and robustness of the observer systems is ensured. Finally, the effectiveness and validity of the proposed control approach is verified by simulation results.

Reduction of Torque Ripple in Induction Motor Drives Using an Advanced Hybrid PWM Technique

Abstract: A voltage source inverter-fed induction motor produces a pulsating torque due to application of nonsinusoidal voltages. Torque pulsation is strongly influenced by the pulsewidth modulation (PWM) method employed. Conventional space vector PWM (CSVPWM) is known to result in less torque ripple than sine-triangle PWM. This paper aims at further reduction in the pulsating torque by employing advanced bus-clamping switching sequences, which apply an active vector twice in a subcycle. This paper proposes a hybrid PWM technique which employs such advanced bus-clamping sequences in conjunction with a conventional switching sequence. The proposed hybrid PWM technique is shown to reduce the torque ripple considerably over CSVPWM along with a marginal reduction in current ripple.

An Improved Equivalent Circuit Model of a Single-Sided Linear Induction Motor

Abstract: The derivation of the equivalent circuit for a single-sided linear induction motor (SLIM) is not straightforward, particularly if it includes longitudinal end effects from the cut-open primary magnetic path, transversal edge effects from the differing widths between the primary lamination and secondary sheet, and half-filled primary slots. This paper proposes an improved series equivalent circuit for this machine. The longitudinal end effects are estimated using three different impedances representing the normal, forward, and backward flux density waves in the air gap, whose two boundary conditions are deduced by introducing the conception of magnetic barrier surface. The transversal edge effects are accounted for by correction coefficient Kt and air-gap flux density correction coefficient Kb. Using the series circuit, the performance of the SLIM was assessed in a similar manner to a rotating induction machine. A 4-kW SLIM prototype was tested, which validated the simulation technique.