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The application of electrical drives in the control of centrifugal fans and pumps is a well-established area that leads to substantial energy savings. It requires electrical and automation engineers to have some knowledge relevant to drives about fan and pump modelling since ignoring or oversimplifying fan/pump modelling for the intended drive design compromises the required control quality. This paper improves the existing dynamical models of fans and pumps integrated with induction motors via neural network estimation of overall fan/pump efficiency; this estimation is based on the voltage frequency of the driving induction motor, pressure, and flow rate, followed by the separation of the fan's or pump's own efficiency for the motor load torque computation, enhancing the accuracy due to the correct reflection of the power balance. The model is developed with a view to being convenient for control design applications. For the first time for dynamical models, it is verified experimentally, justifying the necessity of the first-order nonlinear differential equation for the flow rate. The validation includes a direct approach based on analysis of transient behaviour caused by a small-step perturbation of the frequency of the motor voltages and an indirect approach based on the introduced concept of the dynamical flow rate and pressure estimators. [ABSTRACT FROM AUTHOR]

Most electromagnetic compatibility models developed for the study of three-phase induction machines are generally valid for low and medium frequencies (<< 1 MHz). This frequency limit seems to be too restrictive for the overall study of conducted electromagnetic interference. In this paper, the model is using the proposed model and compared with experimental results in low and medium frequency. And then, the high-frequency modeling of induction motor is presented new method based on transfer function model. The proposed methodology is verified on an experimental and simulation, it’s suitable for prediction of the terminal overvoltage analysis and electromagnetic interference problems and common-mode and differential-mode currents. The novelty of the work consists to develop an improved high-frequency motor model based on transfer function to represent the motor high-frequency behavior for frequency-domain analyses in the frequency range from 40 Hz up to 110 MHz .The purpose of this work is to study the common-mode impedance and the differential-mode impedance of AC motor. The determination of these impedances is done for firstly both common and differential modes at low and medium frequency, and then common-mode and differential-mode characteristics at high frequency. Methods. For the study of the path of common-mode and differential-mode currents in typical AC motor (0.25 kW, 50 Hz) an identification method in high frequency for induction motor has been proposed based on the transfer function in differential-mode and common-mode configuration. The low and medium frequency model were presented in the first time based on equivalent circuit of electrical motor. Then, the common-mode and differential-mode impedances were defined in high frequency using asymptotic approach. This motor was studied by MATLAB Software for simulation and also experimental measurements. Results. All the simulations were performed using the mathematical model and the results obtained are validated by experimental measurements performed in the University of the Federal Armed Forces Hamburg in Germany. The obtained results of common-mode and differential-mode at low frequency, medium and high frequency are compared between simulation and experiment. References 34, table 2, figures 14. [ABSTRACT FROM AUTHOR]

Five-phase induction machines are attractive due to inherent benefits such as lower current rating than three-phase ones. On the other hand, ac motor drives often need to operate in the overmodulation (OVM) region, e.g., to increase the maximum speed or to work with reduced dc-link voltage. Most of the existing OVM strategies for five-phase drives are based on injecting low-order harmonics in the no-torque xy plane while avoiding low-order α−β harmonics (at least up to a modulation index of 1.2311 p.u.), so as to prevent the torque ripple associated with the α−β components. However, in practice the x−y impedance is very small, and hence, this approach can easily lead to overcurrent. This article proposes an OVM method for five-phase induction motors that adaptively modifies the injected components so that at each moment the addition of low-order x−y harmonics is favored over α−β ones but without surpassing the maximum current rms of the drive. In case the total stator copper loss (SCL) tends to exceed its rating during OVM in a given scenario, the proposed scheme automatically reduces the x−y injection to keep the SCL at its rated value. Experimental results verify the theory. [ABSTRACT FROM AUTHOR]

The insertion of dead time will lead to the distortion of output waveforms, which seriously affects the characteristics of the ac induction motor control system. In order to reduce the output distortion of three-level T-type inverters caused by dead time insertion, an online feedback dead time compensation method is developed. In this method, the compensation time is obtained and further corrected by the online feedback of duty cycle. Meanwhile, current polarity judgment is accurately realized by sampling the neutral point (NP) potential and three-phase output terminal voltage potentials. In addition, in this article, we take the NP potential fluctuation into account to approximate the true situation. The developed method can be applied to both open-loop and closed-loop motor drive systems. To verify the effectiveness of the method, essential simulation and experiments are carried out. Compared with the traditional methods, the developed method can prominently reduce the output waveform distortion. Simulation results emphasize that the proposed scheme can significantly improve the performance of three-level inverters, and the identical conclusion is obtained on 210 V/2.24 kW motor platform. [ABSTRACT FROM AUTHOR]

Recently, Direct Torque Control (DTC) of AC motors is considered a significant method to attain torque control behavior compared to DC motors. However, it still suffers from some drawbacks such as the large torque and current ripples. Choice of hysteresis band amplitude is one of the initial difficulties involved in the technique since it determines ripple frequencies and amplitude error of control variables. This paper presents a comprehensive analysis of hysteresis band variations in DTC on the dynamic performance of induction motor (IM) drives. In this concern, effects of flux and torque hysteresis bands on switching frequency, torque and flux ripples as well as current distortion are explored. A simulation model is implemented by Matlab/Simulink. An experimental system of DTC for IM drives using DSP-DS1102 is built and tested. Experimental results are captured to prove the simulation results. The results show that the proposed DTC exhibits a good performance with minimum torque ripples and low current distortion under small hysteresis band amplitudes. However, small hysteresis band amplitudes produce high switching frequencies which cause high switching losses and high computation burden. To guarantee a high dynamic performance DTC of IM drives, a fuzzy logic controller (FLC) instead of a PI speed controller is designed. [ABSTRACT FROM AUTHOR]

Direct torque control "DTC" technique is one of a high performance control system of an AC motor drive, which was proposed after the vector oriented control scheme during the resent 25 years. It has been developed rapidly for its concise system scheme, transient and dynamic performance. The DTC mechanism consists of voltage vector selection table, two hysteresis comparators and two estimator's one for stator flux and another for electromagnetic torque. DTC is directly control torque and flux by using Voltage Source Inverter VSI, space vector and stator flux orientation and indirect speed regulated. A several control techniques can be used for improving the torque and flux performance. In this paper, the DTC with Proportional-Integral-Derivative (PID) controller used to improve the starting and dynamic performance of asynchronous motor AM, which gives good torque and flux response, best speed control and also minimize the unacceptable torque ripple. The mathematical model of DTC with PID controller of 3-phase induction motor IM are simulated under Matlab- Simulink. Therefore, the DTC based on PID controller has good performance of IM compared to classical DTC for starting, running state and also during change in load. [ABSTRACT FROM AUTHOR]

The article presents the analysis by numerical simulation in Matlab- Simulink of the rotor's flux Luenberger observer assembly coupled with a Peng speed observer. The proposed estimator is use in sensorless vector systems of induction motors. [ABSTRACT FROM AUTHOR]

With the increasing proliferation of variable speed drive, the demand for the more reliable drive is also on the rise. Despite the growing interest on more advanced motors like permanent magnet and flux switching motors, three-phase induction motors (3ph-IMs) are still the main workhorse in the industry and hence the fault-tolerant control of these motor drives remains an interesting and important topic. In this paper, a simple fault-tolerant field-oriented control technique for 3ph-IMs is presented. It is shown that by injecting zero-sequence compensation voltage in a feedforward manner, open-circuit faults can be effectively tolerated. Compared to the previous feedforward fault-tolerant control methods, the proposed approach does not require the knowledge of the magnetizing inductance, which is tricky to be obtained in induction motors. Furthermore, the unified feedforward approach allows the same control structure to be used for different fault-tolerant 3ph-IMs drive topologies, with minor modifications to the feedforward terms. In addition, the effect of inverter non-idealities on the performance of the proposed control method is also highlighted and addressed. The effectiveness of the proposed controller is verified using MATLAB simulation and further validated using experimental tests. This paper is accompanied by a video demonstrating the experimental results. [ABSTRACT FROM AUTHOR]

Thyristors are now widely used in many power electronics and motor driven applications and all the known methods of control are nothing but variations of either the phase angle firing control (PFC) or the pulse width modulation control (PWM). Each of these methods has its own benefits and disadvantages, but the pulse width modulation control method is, perhaps, by far, the most effective and costly method. Since PWM differs from phase firing control (PFC) in that the control action of PWM takes place only during the time of the firing pulse, this research seeks to develop a combination firing package that maximizes the benefits of the two methods. At first a thyristor is configured as a PNP-type power transistor latch with two ordinary NPN bipolar switching transistors. The power transistor is switched on by zero crossover firing and then switched off by phase angle delay firing. The performance of the model was evaluated and the dynamic characteristics of the motor, such as speed, current, voltage and the total harmonic distortion were carried via simulation. The results shows that by using the Modified PWM firing technique the speed of an m-phase induction motor can be controlled more effectively and reliably. The circuit is easy to implement and cost effective and may be patented and made available for commercial use. [ABSTRACT FROM AUTHOR]

This article studies the efficacy of a time-scale technique based on DWT for both stator and rotor asymmetries faults detection in WRIMs. The preliminary effort on the RAF detection in IMs relied mainly on the energy evaluation of a known low frequency bandwidth through DWT analysis. It was illustrated that the SCSVM and the IMSC are both good indicators for the RAF monitoring in steady state working conditions of WRIMs. In this work, it will be shown that in the case of any load variation, there is a time-varying DC component that may affect the energy evaluation criterion, resulting in a false alarm. Thus, an efficient method is proposed to estimate and then, to remove this DC component from both SCSVM and IMSC, before the energy evaluation through DWT analysis. Furthermore, by introducing a new frequency bandwidth, associated with SAF in the rotor current signature, this method can be extended to a universal slip independent stator and rotor asymmetries faults detection technique in WRIMs. The proposed approach is validated by experimental tests using a 7.5kW WRIM test rig. [ABSTRACT FROM AUTHOR]

In this work, we propose a new and simple method to insure an online and automatic detection of faults that affect induction motor rotors. Induction motors now occupy an important place in the industrial environment and cover an extremely wide range of applications. They require a system installation that monitors the motor state to suit the operating conditions for a given application. The proposed method is based on the consideration of the spectrum of the single-phase stator current envelope as input of the detection algorithm. The characteristics related to the broken bar fault in the frequency domain extracted from the Hilbert Transform is used to estimate the fault severity for different load levels through classification tools. The frequency analysis of the envelope gives the frequency component and the associated amplitude which define the existence of the fault. The clustering of the indicator is chosen in a two-dimensional space by the fuzzy c mean clustering to find the center of each class. The distance criterion, the K-Nearest Neighbor (KNN) algorithm and the neural networks are used to determine the fault type. This method is validated on a 5.5-kW induction motor test bench. [ABSTRACT FROM AUTHOR]

Since the three-dimensional (3D) analysis of linear induction motor (LIM) needs to consider the transverse end effect, the transverse magnetomotive force (m.m.f.) distribution model becomes significantly important. This study investigates the influences of different transverse m.m.f. models on operating characteristics of double-sided LIMs, and it also develops a novel m.m.f. model. First, four types of hypothetical distribution models are put into a 3D analytical method that considers the longitudinal and transverse end effects. Second, variations of the thrust, lateral and vertical forces with the models are comprehensively investigated in the possible operating regions. Besides, the calculated results are validated by finite elements method results and measurements in a prototype double-sided linear induction motor (DLIM). Finally, the model presented in this study can be considered as a kind of optimal model for analysing DLIMs, and comparisons with other models in each operating region are mentioned. [ABSTRACT FROM AUTHOR]

This paper presents a new active approach in order to design a model-based fault-tolerant control (FTC) system for three-phase induction motors (IMs) subjected to mechanical faults caused by stator and rotor failures. In this approach, a nominal controller achieves control objectives in fault-free case. The main part of this approach is related to design a fault/state observer for simultaneous estimation of additive faults which model the mechanical faults and axial fluxes in any operating conditions. For trade-off between robustness and performance in the presence of uncertainties and faults, this fault/state observer design problem is reduced to a well-known mixedoptimisation problem by using polytopic linear parameter-varying approach. The FTC system consists of a nominal controller together with an observer which provides auxiliary inputs using the estimation of additive faults in order to compensate their undesirable effects on IM performance. The simulation results are shown to illustrate the effectiveness of the proposed approach to compensate the mechanical faults in IM. [ABSTRACT FROM AUTHOR]

This paper investigates the development of a simplified speed control of induction motor based on indirect field oriented control (FOC). An original PI-P controller is designed to obtain good performances for speed tracking. Controller coefficients are carried out with analytic approach. The algorithm is implemented using a low cost Field Programmable Gate Array (FPGA). The implementation is followed by an efficient design methodology that offers considerable design advantages. The main advantage is the design of reusable and reconfigurable hardware modules for the control of electrical systems. Experimental results carried on a prototyping platform are given to illustrate the efficiency and the benefits of the proposed approach. [ABSTRACT FROM AUTHOR]

A new four quadrant Field Orientation-Controlled (FOC) three-phase induction motor drive based on Hysteresis Current Comparison (HCC) has been developed. The direct relationship between current and torque in the Direct-Quadrature (dq) reference frames has been exploited to develop an HCC scheme that offers accurate tracking of current and torque based on the pulse width modulation technique. The parameters of the inner HCC and the outer Proportional-Integral (PI) speed controllers have been optimised to obtain effective current and torque tracking. The complete closed loop system being speed-controlled, four quadrant operation has been obtained using step speed input while the suitability of the developed model has been tested under full load stress during steady state. The results obtained satisfy the four quadrant operation requirements of advanced drives where controlled starts and stops are essential in both forward and reverse directions. This is evident in the effectiveness of current and torque tracking and ease of speed transition from motoring to regeneration and vice versa. The developed model finds applications in advanced industrial drives as an energy-efficient and cost-effective alternative to eliminate the effects of supply voltage drops and mechanical load variations. [ABSTRACT FROM AUTHOR]

This paper presents an input–output feedback linearization (FL) control technique for rotating induction motors, which takes into consideration the magnetic saturation of the iron core. Starting from a new formulation of the dynamic model taking into consideration the magnetic saturation expressed in a space-state form in the rotor-flux-oriented reference frame, the corresponding FL technique has been developed. To this aim, a particular care has been given to the choice of nonlinear functions interpolating the magnetic parameters versus the rotor magnetizing current and the corresponding magnetic characteristic. The proposed FL technique has been tested experimentally on a suitably developed test setup and compared, under the same bandwidths of the speed and flux closed loops, with both the FL technique not taking into consideration the magnetic saturation and with the industrial standard in terms of high performance control of the induction motor: field-oriented control. A further comparison with the unique example present in the scientific literature of the FL control technique including the magnetic saturation has been shown, highlighting consistent improvements achievable by the proposed FL in terms of reduced computational demand and better dynamic performance. [ABSTRACT FROM AUTHOR]

This paper draws a comparative study of the induction motor stator current using Fast Fourier Transform (FFT) and Wavelet transform. The FFT is one of the most popular and oldest techniques used in signal processing to extract the frequency contents of the signal in the steady state. However, it suffers a drawback that in the process of extracting frequency information; the time information gets partially lost. This drawback is compensated by the wavelet transform. This is a new technique which is gaining popularity in many fields of science and engineering. In this paper, a single phase induction motor stator current signal data has been analyzed using FFT and Wavelet in the latest MATLAB environment. It has been shown that these two transform techniques reveals different aspects of a same stator current signal. Keywords: Motor Current Signature Analysis (MCSA), FFT, Wavelet Transform, Current Sensor, Analogue to Digital Converter (ADC), Induction Motor, Condition Monitoring. [ABSTRACT FROM AUTHOR]

Efficiency improvement is an important challenge for electric motor driven systems. For an induction motor, operation under rated conditions (at rated load with rated flux) is very efficient. However, in many situations, operation with rated flux causes low efficiency especially at light load ranges. In these applications, induction motor should operate at reduced flux which causes a balance between iron losses and copper losses leading to an improved efficiency. This paper concerns energy optimization, i.e. efficiency improvement is carried out via a controller designed on the basis of imposing the rated power factor, by finding a relationship between rotor flux and torque current component which can optimize the compromise between torque and efficiency in steady state as well as in transient state. Experimental results are presented to prove the effectiveness and validity of the proposed controller. [ABSTRACT FROM AUTHOR]

This paper investigates the loss manipulation capabilities of deadbeat direct torque and flux control (DB-DTFC) induction machine drives. For each switching period, a volt-second-based inverse model provides a range of volt-second solutions to achieve the desired torque at the end of each switching interval, whereas the stator flux magnitude provides another degree of freedom to manipulate machine losses. With a flux-based DB-DTFC loss model proposed, losses can be manipulated each switching period without compromising torque dynamics. For a steady-state operation and typical process trajectories, the minimum loss can be achieved with corresponding energy savings. Alternatively, significant losses can be rapidly induced to dissipate kinetic energy in a machine during braking transients. This loss maximization technique provides significant braking torque without requiring additional hardware to transfer/dissipate energy. DB-DTFC induction machine drives provide an effective and elegant solution for continuous loss manipulation without compromising dynamic performance. [ABSTRACT FROM PUBLISHER]

The objective of condition monitoring of induction machines is to detect the incipient stage of a fault before serious damage occurs with high associated cost. Although the condition monitoring techniques have been intensively investigated in the last decades, research is still carried out in reducing cost and improving accuracy. This paper proposes a novel method that enables efficient and accurate monitoring of the stator winding circuit fault. The proposed method is based on the sparse grid optimization method applied in the least squares estimation of the circuit parameters that characterize the condition of a fault incipient. The kernel of the method is the efficient search for the objective function minimum on the grid created by using the hyperbolic cross points (HCPs). The system cost and complexity are minimized since the proposed method only requires voltage and current signals recorded at a machine terminal without any invasive or additional hardware circuitry. The proposed HCP algorithm is robust to supply voltage unbalance and motor loading state. The validity and effectiveness of the proposed scheme is experimentally tested on a three-phase 800-W 380-V induction motor. [ABSTRACT FROM PUBLISHER]

Motor current signature analysis (MCSA) based on the 50/60-Hz sidebands has become a common test in industry for monitoring the condition of the induction motor rotor cage. However, many cases of unnecessary motor inspection or outage due to false alarms produced by rotor axial duct interference have been reported. If the number of axial ducts and poles is identical, this can produce 50/60-Hz sideband frequency components in MCSA that overlap with that of rotor faults, resulting in false alarms. However, there currently is no practical test method available for distinguishing rotor faults and false indications other than testing the rotor offline or under the startup transient. In this paper, the feasibility of using the rotor fault frequency component produced by the space harmonic waves is evaluated as a solution for the first time. Since the fifth or seventh space harmonics have a spatial distribution of flux that does not penetrate in the rotor yoke to reach the axial ducts, they do not produce false alarms. The proposed method is verified on 6.6-kV motors misdiagnosed with broken bars via the 50/60-Hz sidebands of MCSA. It is shown that it provides reliable online indication of rotor faults independent of axial duct influence and can be used for screening out false alarms. [ABSTRACT FROM PUBLISHER]

A look at techniques to reduce losses in induction electric motors which are aimed to meet the efficiency level IE4 (IEC 60034 30). This article also discusses the rules, guidelines and the best practices to reduce losses in induction electric motors, examining new technologies to improve efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a technique which improves energy efficiency of AC rotating machines by using Grain Oriented (GO) steel at stator core instead of Non Oriented (NO) steel. The losses of GO steel are lower than the NO ones, but only when the magnetic flux circulates along the rolling direction; consequently it is rarely used in AC machines where the magnetic flux rotates. By stacking many shifted GO laminations of AC machine stator, the flux pass from one lamination to another, and the core losses are reduced. A lot of experimentations have been done with unidirectional field, rotating field and with real induction machines. They show important improvements with GO shifted steel. The efficiency difference between a classical 10 kW induction machine and a modified machine with GO stator is more than 2 points. Moreover, the no-load current, and so the reactive power are smaller. This technique creates environmental and financial gains. [ABSTRACT FROM AUTHOR]

AC motor drives are used in multitude of industrial and process applications requiring high performances. In high performance drive systems the motor speed should closely follow a specified reference trajectory regardless of any load disturbances and any model uncertainties. The controllability of torque in an induction motor with good transient and steady state responses form the main criteria in the designing of a controller. Though, PI controller is able to achieve these but with certain drawbacks. The gains cannot be increased beyond certain limit so as to have an improved response. Also it deteriorates the controller performance. With the advent of artificial intelligent techniques, these drawbacks can be mitigated. Base on the inability of conventional control methods like PI, PID controllers to work under wide range of operation. Artificial intelligent based controllers like ANN, Fuzzy controller, ANFIS, expert system, genetic algorithm are widely used in the industry. But, the main problem with the conventional fuzzy controllers is that the parameters associated with the membership functions and the rules depend broadly on the intuition of the experts. In this paper Fuzzy and ANFIS based control of induction motor is done. ANFIS performs better than the conventional and fuzzy and proves be more reliable. [ABSTRACT FROM AUTHOR]

The most complete definition for the voltage unbalance is using complex voltage unbalance factor (CVUF) that consists of its magnitude and angle. Unfortunately, the definition did not distinguish between undervoltage and overvoltage unbalance conditions. In this paper, the analysis of the motor is performed using the method of symmetrical component and MATLAB software is used to investigate the performance of induction motor. The simulation results show that the International Electrotechnical Commission (IEC) definition of the voltage unbalance can be applied to evaluate total copper losses precisely. However, the phase angle of unbalance factor must be included for accurate predicting of peak currents and peak copper losses of the phase windings of the motor. The unbalanced conditions which distinguish between under and over voltage unbalance must also be taken into consideration for assessing all the quatities. [ABSTRACT FROM AUTHOR]

In this paper we develop an approach based on residue analysis of stator currents to detect and diagnose faults eccentricity static, dynamic and mixed in three phase induction motor. To simulate the behaviour of motor failure, a model is proposed based on the approach of magnetically coupled coils. The simulation results show the importance of the approach applied for the detection and diagnosis of fault in three phase induction motor. [ABSTRACT FROM AUTHOR]

In this paper we have addressed the most frequent faults in induction machine threephase squirrel-cage, as the broken rotor bars and defects static and dynamic rotor eccentricity. The method of detecting these defects is based on frequency analysis of measurable quantities of the machine. In general we consider the stator current because it is easily measurable, significant when signatures match those on electromagnetic quantities. Despite changes in diagnostic methods, this method of analysis is effective to be used as a diagnostic technique and early detection of operating condition of the machinery in industrial plants. First, a modeling and simulation study on the defect model is presented. The first time we have developed the mathematical model of the machine, and then the simulation results are presented to illustrate the influences of these defects on the operational status of the machine. [ABSTRACT FROM AUTHOR]

The performance and efficiency of an induction motor drive system can be enhanced by online estimation of the critical parameters, such as the rotor time constant and stator resistance. A novel sliding mode observer with parameter identification is proposed in this paper to compensate the parameter variation effects. The (SMC) technique finds its stronger justification in the utilization of a robust nonlinear control law to model uncertainties. The used control algorithm is a sliding mode associated with a particular function "sat" to limit chattering effects that presents a serious problem in applications to variable structure systems such as electric propulsion. The observer is simple and robust, and suitable for online implementation for EV application. Simulation tests under load disturbances and parameter uncertainties are provided to evaluate the consistency and performance of the proposed control technique. [ABSTRACT FROM AUTHOR]

Three control schemes for the operation of induction motors in the field-weakening region are compared and assessed in terms of performance and complexity. These three control schemes fully utilize the maximum available voltage and current at any speed, and thus provide the maximum possible torque in the entire field weakening region. For the comparison, the three control schemes were implemented on the same experimental platform, i.e. the same Digital Signal Processor (DSP) board, power inverter and motor drive. In this way, it is possible to judge not only the performance of each solution, but also its requirements in terms of computational time, tuning complexity, parameter knowledge and stability of operation. [ABSTRACT FROM AUTHOR]

This article is the first of a series of three that examines the correlation between off-line and on-line measurements on Type I random-wound motors. The off-line tests reported in this first article were carried out according to IEC 60034-18-4 to demonstrate that they are PD free under impulsive voltage conditions. [ABSTRACT FROM AUTHOR]

Due to its simple construction and excellent mechanical/ thermal stress withstanding capability, induction motor with solid-rotor structure is widely used in many high-speed, high pressure application fields. In this paper, a novel solid-rotor induction motor with skewed slits in both radial and axial directions is presented. The performance of the proposed solid rotor is simulated using time stepping finite element method (FEM). Because of the existence of the axial slits, the magnetic flux in the slit-rotor motor can penetrate, relative to those without slits, deeper into the rotor. Analysis shows that its torque is about 3.46 times of that of the motor with no rotor slits. By skewing the rotor slits in the radial direction in the novel motor being proposed, the torque is further increased by about 37.7% when compared with that of the motor with its rotor slits not skewed along the radial direction. Although more torque ripples are generated in rotors with skewed slits in the radial direction, it is shown that the torque ripples can be easily reduced by skewing of the slits along the axial direction. [ABSTRACT FROM AUTHOR]

Abstract: In this paper an integrated approach for on-line induction motor fault detection and diagnosis is presented. The need to insure a continuous and safety operation for induction motors involves preventive maintenance procedures combined with fault diagnosis techniques. The proposed approach uses an automatic three step algorithm. Firstly, the induction motor stator currents are measured which will give typical patterns that can be used to identify the fault. Secondly, the eigenvectors/eigenvalues of the 3D current referential are computed. Finally the proposed algorithm will discern if the motor is healthy or not and report the extent of the fault. Furthermore this algorithm is able to identify distinct faults (stator winding faults or broken bars). The proposed approach was experimentally implemented and its performance verified on various types of working conditions. [Copyright &y& Elsevier]

This paper addresses the causes of synchronous torques in split-phase induction motors. First, an analytical model is outlined to describe the processes involved in producing synchronous torques. This involves the consideration of the motor MMFs interacting with the slot permeances. The results from the implementation of the model are given for several different motor designs to calculate the synchronous torques. These highlight the way that the synchronous torque is a function of the MMF and slotting relationships. Measurement of the synchronous torque is not straightforward; however, a method of assessment is developed in this paper by using a deceleration test and other tests. The test results are fully described in this paper, and they illustrate that even with correct bar/slot combinations and skew, synchronous torques still exist in the machine. [ABSTRACT FROM AUTHOR]

This paper addresses two types of additional losses in induction motors. One is stray load loss resulting from loss segregation when induction motors operate from a sinusoidal supply voltage and the other is harmonic loss when induction motors operate from inverter-fed supply voltage. Both losses are of concern in machine design and operation but they are difficult to predict accurately without the use of empirical factors. This is due to their complex loss mechanisms and small magnitudes relative to output power for high efficiency machines. Compared to total machine power loss, however, they are a significant source of loss. Investigation into the correlation of the two loss components could enable effective quality control of the manufacturing of machines for use on inverter supplies. With the availability of advanced calorimetric and harmonic injection techniques, it becomes possible for these small loss components to be measured with precision. In this paper, seven induction motors ranging in power through 1.1, 7.5, 15 to 30 kW are tested for experimental comparison. Among these are four 7.5 kW machines. Test results suggest there is a need for induction motors designed specifically for inverter-fed operation. [ABSTRACT FROM AUTHOR]

In the recent years and with the strong technological development of semi conductors, the three phase induction motor is one of the most used electric machines in variable speed system in the different field of industry. Good reability of power electronic systems is essential not only for security system and for people but also to reduce coasts of maintenance. The rapid and accurate diagnosis of any system employing electrical drive system remains one of the current problems. This paper presents three methods and fault detection and isolation of an AC drive system under open fault conditions in the inverter through modeling and simulation of the system. The proposed methods are achieved by using open circuit in the inverter. The obtained simulation results show clearly the possibility of extracting signatures to detect and isolate faults. [ABSTRACT FROM AUTHOR]

In this paper, a new method for detecting the presence of broken rotor bars is presented. The proposed approach is valid for induction machines started at constant frequency and consists of extracting the instantaneous frequency (IF) of the left sideband harmonic (LSH) from the start-up current (LSHst), via the Hubert transform. It is shown that, in the case of machines with one or several broken bars, the IF of the LSHst exhibits a very characteristic and easy to identify pattern, which is physically justified. This paper also shows that, if the IF of the LSHst is represented against the slip, a universal fault indicator (nondependent neither on the machine characteristics nor on the starting conditions) can be defined. This fault indicator consists of the correlation between the experimental IF of the LSHst and its theoretical evolution. This approach is theoretically introduced and experimentally validated by testing a commercial motor in faulty and healthy conditions, under different operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation into suitable torque control schemes for an electric vehicle application. The electric vehicle drive train consists of rewound induction motors and a three-level IGBT inverter switching at 10kHz. The schemes investigated are Direct Torque Control DTC with two-level IGBT inverter, and DTC with threelevel IGBT. The results of Matlab- Simulink simulations and a comparison between the control schemes are presented. It is found that the DTC using three-level IGBT scheme is best for this application. [ABSTRACT FROM AUTHOR]

Field aligned starting (FAS) is a technique for starting three-phase cage induction motors on either three-phase or single-phase supply lines under varying load conditions with minimal inrush currents. The technique starts the motor independent of the mains supply with a high transient torque before connecting the spinning motor to the mains. It is imperative to the operation of FAS that the spinning motor be connected to the mains at the correct time. Incorrectly timed mains connection can result in negative transient torques with the severity to slow, or possibly stall the already started motor. As the implementation of FAS is not possible without a predictive mechanism by which the correct moment of mains connection can be found in advance, this paper proposes a simple, low cost, yet effective self-calibrating method which ensures that the timing of the mains connection is correct under all starting conditions. Critical issues vital to a successful self-calibration under transient and varying starting conditions are investigated and presented with both experimental and simulated results to show that self-calibration is an indispensable part of FAS technique. [ABSTRACT FROM AUTHOR]

This work proposes an equivalent circuit model for a stand-alone three-phase self-excited induction generator (SEIG) with unbalanced load impedances. The SEIG supplying unbalanced loads is modelled by a two-port network that allows the steady-state performance of the generator to be analysed more easily and more efficiently. The proposed model is validated by experiments on a 0.5 Hp cage-type induction motor operated as a generator. [ABSTRACT FROM AUTHOR]

The switched reluctance (SR) motor has many benefits owing to its low cost, simple design, rugged construction and comparatively high torque-to-mass ratio. Unlike DC and induction motors, the SR motor is intended to operate in deep magnetic saturation to increase the output power density. Because of the saturation effect and the variation of magnetic reluctance with respect to rotor position, all the relevant characteristics of the machine are highly non-linear functions of both rotor position and phase current. The ultimate outcome of all these non-linearities is that the generated torque contains significant ripples. The non-linearities in the SR motor have been extensively studied and many control strategies to reduce the generated torque ripples have been proposed in the literature. Modulation of phase current profile for generating torque in the SR motor with minimum ripples was the focus of most of the research. However, the main challenge to minimise the torque ripple is to design a current controller that is able to track the modulated phase current. In this work, new techniques to optimise the widely used hysteresis current controller are studied, and experimental verifications under closed-loop speed control with the modulated reference current data are presented. The experimental results indicate that the torque ripple is reduced to lie within 5% of the desired steady torque using the proposed optimisation techniques. [ABSTRACT FROM AUTHOR]

The thyristor-based current source inverter (CSI) fed ac machine drives are often employed in high power applications. However, the thyristor-based CS! has intrinsic drawbacks because the thyristors cannot be turned off by the gating signals. Therefore, external circuits are required to turn the thyristors off by using reverse-biased voltages, as well as transfer reactive energies of inductive loads after turning off the thyristors. This paper presents a hysteresis modulated CSI drive which overcomes all these drawbacks and results in sinusoidal motor voltage and current even with CSI switching at fundamental frequency. The proposed CSI drive uses a voltage source inverter as an auxiliary circuit replacing the bulky ac capacitors used in the conventional drive. Then an indirect field oriented controlled CSI drive based on proposed configuration is developed. The simulation results are presented. Simulation results show that the proposed drive has stable operation even at low speeds. [ABSTRACT FROM AUTHOR]

Abstract  In this work, the low frequency electromagnetic flux density around induction motors is studied; the main objective is to provide safety regions for humans in the vicinity of these motors, especially in electrical vehicles, where high currents and hence high flux density emissions are expected. A new equivalent magnetic circuit which accounts for stray magnetic fields is developed. The analysis shows that the emission of the stray field in the radial directions depends on the permeability of the stator body as well as the ampere turn of the stator winding. Small values of stator body permeability may result in very high stray flux emissions at levels that may require shielding to protect passengers just above the motor. Relatively far away from the stator (e.g., 50 cm for the tested motors), the flux is normally of low level and may not represent an exposure threat. [ABSTRACT FROM AUTHOR]

Recently, the development of speed estimation methods for sensorless control of induction motor drives has found great interest in the research community. Parameter adaptation schemes play an important role for better speed estimation over a wide range from zero to high levels beyond the rated speed. Therefore, parallel identification schemes for both speed and stator resistance of sensorless induction motor drives are proposed for a wide range of speed estimation. These estimation algorithms combine a sliding-mode current observer with Popov's hyperstability theory. Low- and zero-speed operations of the proposed sliding- mode-observer (SMO)-based speed estimation combined with an online stator resistance adaptation scheme, are investigated. A modified SMO-based speed estimation scheme for field-weakening operation is also introduced. The mismatch problem of magnetizing inductance in the field-weakening region is treated by an online identification scheme. Magnetizing inductance, estimated in this way, is further utilized within the SMO, so that the main flux saturation variation is taken into consideration. The performance of the proposed SMO and its speed estimation accuracy, with an indirect field-oriented controlled induction motor, are verified by simulation hind experimental results over a wide speed range from zero to high values beyond the base speed. [ABSTRACT FROM AUTHOR]

This paper develops a seven-level inverter structure for open-end winding induction motor drives. The inverter supply is realized by cascading four two-level and two three-level neutral- point-clamped inverters. The inverter control is designed in such a way that the common-mode voltage (CMV) is eliminated. DC-link capacitor voltage balancing is also achieved by using only the switching-state redundancies. The proposed power circuit structure is modular and therefore suitable for fault-tolerant applications. By appropriately isolating some of the inverters, the drive can be operated during fault conditions in a five-level or a three-level inverter mode, with preserved CMV elimination and dc-link capacitor voltage balancing, within a reduced modulation range. [ABSTRACT FROM AUTHOR]

This paper presents a method for improving the control design for a high-power induction motor (IM) drive employing rotor-flux-based orientation. An offline genetic-algorithm routine is used to estimate the electrical and mechanical parameters of the machine using only speed transient measurements. This routine is applied to a range of operating conditions to obtain an accurate knowledge of the IM parameters as a function of the d-axis motor current id. The information acquired is then employed, together with an enhanced control design obtained by optimizing speed and current transient responses, to increase the performance of the vector control algorithm. The effectiveness of this design method is demonstrated through a wide range of simulations using Matlab-Simulink and experimental results at power levels up to 230 kW. [ABSTRACT FROM AUTHOR]

A model-based predictive control of rotor flux and speed of a vector-controlled induction motor (IM) is presented. A state-space approach is employed for modeling a rotor-flux- oriented IM. The control law is derived by optimization of an objective function that considers the control effort and the difference between the predicted outputs (speed and rotor flux) and the specific references, with predicted outputs calculated using a linearized state-space model. The rotor flux and speed are estimated by using an extended Kalman filter. In this model, the load inertia is unknown, and the external load torque is considered to be a disturbance. Its amplitude is computed with the electromechanical equation or estimated by the Kalman filter. Simulated and experimental results show the good performance of this strategy. [ABSTRACT FROM AUTHOR]