ADJUSTABLE SPEED DRIVE

The paper presents a new algorithm for process the signals delivered by an inverter, necessary to power an electrical induction motor. The proposed algorithm, based on a Least Mean Square (LMS) adaptive filtering method, estimates in real-time the harmonics and interharmonics that affect the fundamental frequency of power supply voltage. The application in which the algorithm is involved is designed to monitor ten bands of harmonics along with their interharmonics. The presented method reveals better performances than other conventional measurements methods, mainly due to its possibility of realtime implementation.

The suitability of the direct modular multi-level converter for high power, low speed, gear-and transformerless drives is investigated. Control methods which optimize the capacitor voltage ripple are presented, analyzed and verified in simulation.

Proper use of adjustable speed drives (ASD's) in any application requires informed considerations of many issues. When that application is an integral part of a continuous process, the implications of those considerations, in financial terms, can be greatly magnified. By definition, in this paper, a continuous process is any process in which the product being manufactured flows through the manufacturing cycle with no interruption or intermediate storage or lag. Therefore, any interruption to that process will halt the entire manufacturing flow, with implications ranging from just lost production to extremely costly implications like repair, re-stringup, or removal of polymers that have "set up" in piping, etc. Paraphrasing a real estate motto, when applying ASD's in a continuous process, the three most important factors are reliability, reliability, and reliability. The requirement for the high level of reliability, along with state-of-the-art potential solutions dealing with power quality issues, will be presented.

Robust speed control of a low damped electromechanical system with backlash is studied, controlled load angular speed being not measured. The proposed control strategy combines a Luenberger observer (load angular speed and load torque disturbance estimations) and a robust CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench.

This paper deals with modelling the induction machine with dynamic eccentricity fault. The machine inductances are calculated using the magneto motive force and the air gap permeance approach taking into consideration the space harmonics effect. First, the magnitude and the form of the obtained inductances in presence of dynamic eccentricity are discussed and compared to those of the healthy machine. Next, these inductances are introduced in the general induction machine model obtained using the magnetically coupled circuits approach. Simulation results illustrate the induction machine performances for the healthy and the faulty cases. The Fast Fourier Transform (FFT) of the steady state stator current obtained by simulation is performed to detect specific components that identify the fault appearance in the machine. The detection of these components is easier when the motor is supplied from a sinusoidal voltage than when supplied from a Pulse Width Modulation (PWM) inverter.

A considerable number of nonlinear industrial loads employ three-phase inductive filters to reduce their peak currents and mitigate the conduction of harmonic currents into the supply system. In modeling and analysis of this kind of filter, the fact that-for reasons of economy-they consist of a single block where the three electrical phases share the same magnetic core instead of having three single-phase reactors is often overlooked. Since the three windings are coiled in the same plane, the central magnetic limb of the core has a lower magnetic reluctance than do the lateral limbs. Moreover, this undesired effect is increased by the existence of internal magnetic couplings. The above phenomenon, which might, at first sight, be considered negligible, will become noticeable in real electrical facilities because of the particular operating conditions of three-phase inductive filters. The aim of this paper is, thus, to present a new model for three-limb core three-phase inductive filters that includes all the above parasitic effects and to describe its practical application in order to assess the magnitude of the errors produced by traditional models when estimating real filter behavior.

A comparison between a matrix converter and a back-to-back converter feeding a passive load is presented in this paper, with the aim of determining the converter topology which yields the highest output power per switches number. The comparison has been performed for different values of the output frequency. For each output frequency the load power has been increased until one of the switching devices reaches the maximum thermal stress, so defining the maximum output power of the converter. For this purpose, a simplified thermal model has been used to evaluate the junction temperature of the switches on the basis of the switch losses. An accurate computer model of both converters has been implemented taking into account the modulation laws and the real characteristics of the switching devices. Simulation results are presented showing the different behaviour of the two converters as a function of the output frequency. It has been verified that matrix converters perform better than back-to-back converters at low output frequencies.

Predictive current control methods for forced-commutated converters, e.g., voltage source inverter, are well documentated and they perform very well compared with the classical solutions, i.e., hysteresis control and proportional-integral controllers with pulsewidth modulation. This paper presents a strategy to implement a predictive control technique for a naturally-commutated converter, e.g., multipulse cycloconverter. This strategy uses a discrete-time model of the system to predict the future value of the load current for all possible output voltages of the converter. Since in a naturally-commutated converter the possible output voltages are dynamic and they depend on the present switching state of every semiconductor of the converter, these output voltages must be obtained from a mathematical model (finite-state machine) of the converter. The proposed current control strategy is tested. The simulation and experimental results show that a predictive control strategy can be used ...

Adjustable-speed drives involve common-mode voltages, which generate common-mode currents flowing to the ground through stray capacitances of electric machines. These currents are known to provoke premature motor-bearing failures, as well as electromagnetic interferences disturbing neighbor electronic devices. Furthermore, high-voltage applications involve high levels of these conducted emissions, which must be lowered by using bulky and expensive filters. This paper aims at elaborating a new pulsewidth-modulation (PWM) strategy in order to reduce the common-mode currents generated by threelevel neutral-point-clamped inverters. The proposed strategy also provides the ability to balance the neutral point of the dc-bus capacitors. Experimental results both in time and frequency domains confirm that the new PWM improves the electromagneticcompatibility behavior of the drive compared with conventional strategies.

Voltage sags are considered one of the most important Power Quality (PQ) problems in industrial plants. Voltage sags are defined as voltage reduction events, followed by restoration of the normal supply conditions after a short duration. During sag, induction motors may not continue its normal operation and may trip or shut down. Induction motors constitute a large portion of the loads in industrial power systems. The loss of their service in a continuous process plant (like a refinery) may result in a costly shutdown. The basic observed effects of voltage sags on induction motors are speed loss and current and torque transients associated with both voltage reduction and recovery. The response of induction motors to voltage sags differ depending on the characteristics of voltage sag such as sag magnitude and duration, as well as the electrical parameters of the motor and load characteristics. This paper will focus on the response of the induction motors to voltage sags. In addition to the well-known parameters of voltage sags (magnitude and duration), other characteristics which drew a little or no interest in the literature will be investigated, such as pre-sag voltage, point on the wave at sag occurrence/recovery, percentage of loading, and presence of harmonic distortion. Other objective of this study is to investigate the motors ride through capability during different types of voltage sags. Finally, recommendations for adjusting the protection relays of the motors are pointed. The industrial electrical distribution system at Alexandria National Refining and Petrochemicals Co. (ANRPC) is taken as a case study to investigate such effects through computer simulations using the MATLAB/SIMULINK toolbox. Validity of the simulations is verified by actual performance.

Voltage sags are voltage reduction events, followed by restoration of the normal supply conditions after a short duration. Induction Motors (IMs) constitute a large portion of the loads in industrial power systems. The loss of their service in a continuous process plant (like a refinery) may result in a costly shutdown. The basic observed effects of voltage sags on induction motors are speed loss and current and torque transients associated with both voltage reduction and recovery. This paper will focus on the response of the IMs to various parameters of voltage sags; including magnitude, duration, effect of pre-sag voltage, loading percentage, point on the wave of sag occurrence, source harmonics, and three-phase unbalance. Other objectives of this study are to investigate the motors ride through capability during different types of voltage sags, and to establish guidelines for adjusting the protection relays of the IMs. The industrial electrical distribution system of Alexandria National Refining and Petrochemicals Co. (ANRPC) is taken as a case study to investigate such effects through computer simulations using the MATLAB/SIMULINK toolbox. Validity of the simulations is verified by actual performance.

The paper focuses on a comparative analysis of direct torque control (DTC) space vector modulation (SVM) based permanent magnet synchronous motor (PMSM) drive. This comparative analysis is based on a conventional inverter and a 3-level dual-cell modular multilevel inverter (DCMLI) using the SVM technique using MATLAB simulation. The present DTC-PMSM drive consists of flux and torque hysteresis comparators and has a problem of switching frequency and torque ripple. The problems are solved by using SVM to provide more inverter voltage and it compensates for torque and flux error in a DTC. A reference voltage space vector is calculated every time using the algorithm on the basic of torque error and stator flux angle. It was proposed to control torque, torque angle, and stator flux in DTC-PMSM. From the detailed comparison, the DTC-DCMLI PMSM drive has an exact solution of problem-solving of switching frequency and torque ripple due to less distorted output. Proposed drives can be applicable for hardware implementation in automotive applications.

This paper develops the foundations of a technique for detection and categorization of dynamic/static eccentricities and bar/end-ring connector breakages in squirrelcage induction motors that is not based on the traditional Fourier transform frequency domain spectral analysis concepts. Hence, this approach can distinguish between the "fault signatures" of each of the following faults: eccentricities, broken bars, and broken end-ring connectors in such induction motors. Furthermore, the techniques presented here can extensively and economically predict and characterize faults from the induction machine adjustable speed drive design data without the need to have had actual fault data from field experience. This is done through the development of dual-track studies of fault simulations and hence simulated fault signature data. These studies are performed using our proven Time Stepping Coupled Finite Element-State Space method to generate fault case performance data, which contain phase current waveforms and time-domain torque profiles. Then from this data, the fault cases are classified by their inherent characteristics, so called "signatures" or "fingerprints". These fault signatures are extracted or "mined" here from the fault case data using our novel Time Series Data Mining technique. The dual-track of generating fault data and mining fault signatures was tested here on dynamic and static eccentricities of 10% and 30% percent of airgap height as well as cases of 1, 3, 6, and 9 broken bars and 3, 6, and 9 broken end-ring connectors. These cases were studied for proof-of-principle in a 208-volt, 60-Hz, 4-pole, 1.2-hp, squirrel cage 3-phase induction motor. The paper presents faulty and healthy performance characteristics and their corresponding so-called phase space diagnoses that show distinct fault signatures of each of the above mentioned motor faults.

The aim of the paper is to present a diagnostic system for shaft misalignment detection. The diagnostic system is used in an adjustable speed sensorless induction motor (IM) drive with an inverter output filter. A nonlinear control algorithm and state observer were used in the motor control. Because the inverter output filter was installed in the drive, the control structure, as well as the estimation systems, were adequately changed. The adaptive neuro-fuzzy inference system (ANFIS) is used for shaft coupling fault detection. ANFIS is based on the analysis of the stator current, motor speed, and load torque processing. ANFIS uses only signals estimated from the state observers whereas observers calculate required variables only on the base of the inverter input voltage and two output current sensors. No additional special sensors are required. The proposed diagnostic system clearly indicates the shaft misalignment. The paper presents the model of the drive, control and estimation algorithms, as well as the diagnostic system. Whole drive and ANFIS fault indicator were verified by experiments for a 1.5 kW induction motor drive system.

The first part of paper describes step by step installation of Switched Reluctance Motor & its drive. A special procedure for installation (Mechanical as well as Electrical) is developed in order to reduce acoustic noise, EMI interference and torque ripple of a motor. A serious electrical interference problem is solved using special designed screened cable. The second part of paper describes dynamic simulation of SR Motor using analog behavioral modeling using Pspice software. The third part of paper presents mechanical modeling mechanical modeling & simulation of the SR Motor. General Terms Electromagnetic Testing, EMI Interference, ZX subcomponent

This paper describes a generalized model of the three-phase induction motor and simulation of the direct self-control (DSC) system, using the Matlab Simulink software. The advantage of Simulink modelling is that program compilation is not required. Instead, the mouse and Simulink menu commands are used to link the basic function blocks to yield the complete DSC system simulation model. This paper also shows the techniques to simplify and solve high-order and nonlinear equations in the design of the DSC system. It is also demonstrated that the DSC method is sensitive to the current sensor noise and the controller time delay.

This paper discusses the performance of different current control schemes used in shunt active power filters. The controller schemes are linear PI regulator, hysteresis control, and a regulator based on the dead-beat controller. The feasibility of the three control schemes have been tested with different waveform and the results are compared through the mean error and root mean square error between the current active filter and the reference current and the total harmonic distortion of both currents. Finally, the modified dead beat controller is applied to a shunt active filter designed for mitigating harmonics injected by an adjustable speed drive.

Utility capacitor-switching transients (CSTs) are responsible for numerous nuisance tripping of PWM adjustable speed drives (ASDs) and result in costly down times. During a CST event, the dc link voltage of the ASD can momentarily rise to greater than 1.3 p.u. resulting in nuisance tripping. In this paper, a new approach to mitigate nuisance tripping of PWM ASDs is discussed. In this approach, the soft-charge resistor available in most ASDs, is momentarily introduced in the series path of the power flow to effectively damping the CST. Further, damping effect is electronically adjusted. The proposed approach demonstrates a method that can be incorporated within an ASD to electronically damp the oscillatory transient generated during a CST event. The advantages of the proposed approach are i) electronic damping for CST event is achieved by low cost modifications to ASD hardware; ii) it adapts to several utility resonance conditions. The required additional hardware for ASDs to be immune to CSTs, can be viewed as an add-on option. This paper discusses the analysis, simulation and experimental performance on a 480 V, 16 kVA commercial ASD equipment.

Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower copper loss than the MTS for any given torque, but a smaller torque operation range. The full-range MLS (FRMLS) has recently been proposed, providing minimum copper loss, for each torque value, in the whole torque operation range (the MTS torque operation range); however, only one OP was considered. Furthermore, neither the torque operation range of the MLS nor the copper loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This letter evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases the FRMLS is substantially better than the MTS and MLS in terms of copper loss and torque operation range. Experimental results verify the theory. Index Terms-Dual three-phase machine (D3PM), fault tolerant control, multiphase drives, variable speed drives. ACRONYMS D3PM Dual three-phase machine. FRMLS Full-range minimum-loss strategy. OP Open phase. MTS Maximum-torque strategy. MLS Minimum-loss strategy I. INTRODUCTION D UAL three-phase machines (D3PMs), a.k.a. asymmetrical six-phase machines, are an attractive alternative to three-Manuscript

Adjustable-speed synchronous motors (ASSM) are very popular in high-power high-speed applications. The Chilean mining industry uses them in milling operations in ranges of several thousands hp. Although a high pulse number for the inverter would be beneficial, it never goes beyond 12, due to complicated connections. Thus, a distorted harmonic-rich current feeds the synchronous motor, increasing the inverter commutation angle and causing additional rotor-heating and pulsating electric torque. Harmonic suppression by filters is not viable due to the variable frequency nature of the motor. In this paper a new design for the inverter, without complicated circuitry, is proposed, so that it works with 36 pulses and then the motor is fed with a highly sinusoidal current. Also, the same technique is applied to the rectifier end, so that an effective harmonic reduction is carried out at both ends of the system, i.e., the motor as well as the ac supply system. A 20-KVA laboratory development drive system has been built and experimental waveforms for the conventional (12-pulse) and proposed (36-pulse) configurations are included.

Dear Mr. Hingtgen, My name is Samuel Milham. I'm a physician-epidemiologist and have been studying the health effects of electromagnetic fields for over 30 years. I have written a book about it called "Dirty Electricity", and have a website: www.sammilham.com. I have measured many residences with roof-top solar, and find that they all generate dirty electricity. I recently began study of a 23 megawatt solar facility near Niland CA. The inverters, switchgear room and substation were all loaded with high frequency transients. The attached oscilloscope tracings show a contaminated 60 Hz sine wave in the A block and that data block B ,which has voltage passed though a high pass filter to remove the 60 Hz, has 45 V of electricity. I went through hundreds of other scope tracings I have made over the years, and found none that were above 2 V in the B block. The harmonic distortion is low, so all this electricity must be transients. I enlarged that blue curve and found that th...

Multiphase machines (MPMs) have become serious contenders in several applications, such as offshore wind energy and electric vehicles. Low-order current harmonics arise in actual drives due to converter and machine nonlinearities, thus producing losses and torque ripple. In comparison to three-phase machines, in MPMs this effect is aggravated because of the existence of low-impedance subspaces. To cancel these harmonics, a multiple resonant controller (RC) (MRC) structure has recently been proposed for MPMs, which combines RCs and synchronous frames (SFs). The MRC scheme allows a significant computational saving in comparison to the multiple SF (MSF) strategy, which includes a proportional-integral controller in an SF per each harmonic. However, such MRC method is only suitable for MPMs with symmetrical winding arrangement (SWA), while asymmetrical winding arrangement (AWA) is also a common choice. In this paper, the MRC strategy is extended to MPMs with AWA. Different neutral configurations, whose effect on the harmonic mapping is more complicated than for SWAs and has hardly been studied so far, are considered. The optimum combinations of frequencies at which the RCs and the SFs should be tuned for AWAs are assessed. Simulation results are provided.

Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower copper loss than the MTS for any given torque, but a smaller torque operation range. The full-range MLS (FRMLS) has recently been proposed, providing minimum copper loss, for each torque value, in the whole torque operation range (the MTS torque operation range); however, only one OP was considered. Furthermore, neither the torque operation range of the MLS nor the copper loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This letter evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases the FRMLS is substantially better than the MTS and MLS in terms of copper loss and torque operation range. Experimental results verify the theory. Index Terms-Dual three-phase machine (D3PM), fault tolerant control, multiphase drives, variable speed drives. ACRONYMS D3PM Dual three-phase machine. FRMLS Full-range minimum-loss strategy. OP Open phase. MTS Maximum-torque strategy. MLS Minimum-loss strategy I. INTRODUCTION D UAL three-phase machines (D3PMs), a.k.a. asymmetrical six-phase machines, are an attractive alternative to three-Manuscript

The paper presents an analysis of the voltage sags effects on induction machine operation. The comparison of the numerical analysis and experimental measurements is presented. Wide range of 3-phase voltage sags was analyzed and measured. The measurement was done by use of the programmable 15kW AC power source CI15003iX.

Electromagnetic compatibility (EMC) has become an important area of electrical engineering in automotive industry. Testing standards and regulations imposed by governments and other agencies have forced companies to pay close attention to the electromagnetic properties of their products. Nedap Specials Automotive has developed and produced Sunroof Control Units (SCU) for more than 10 years. The SCU is assembled to build a sunroof system with a low-cost DC (Direct Current) motor and a sunroof structure, which are purchased from other suppliers. EMC is one of the most important concerns in the designing of SCU, because automotive products meet tighter EMC regulation, especially in the limitation for transient noise. On the other hand, with the adopting of Pulse Width Modulation (PWM) in a new product, additional electromagnetic interference (EMI) is gained, which even causes the EMI level of this product to go beyond the standard. To reach electromagnetic compatibility it is important to consider EMC in an early stage of design. That is, try to prevent a noise from occurring by optimizing crucial designable parameters. In this report, models of switch, relay, cable, motor and SCU are firstly developed in PSPICE so that the potential noise sources can be pointed out. Some models are validated by experiments. Our experience and the analysis and experiments described in this report show that the EMI is unwanted oscillatory current or voltage noise sources originated by transient. The transient may be opening and closure of switch, bouncing of relay, switching of MOSFET or commutation of motor, etc., and potential noise sources produced by transient will conduct and radiate interference to surrounding. Radiation models are constructed to find correlation between noise source and radiated emission. One model used in predicting radiated emission in low frequency has been presented and the condition for use is described. Experiences from former designs show that many designable parameters can determine how severely a transient causes EMI. Base on these validated models, the evaluation of designable parameters becomes feasibly. Unfortunately, changing some parameters makes benefit and disadvantage simultaneously in suppressing EMI which generated by different causes. Therefore, a compromise has to be found, and some configuration parameters that do not significantly affect EMI behavior can be discarded. Synthesis is done at last to get optimized configuration for designable parameters. i Contents Chapter 1 Introduction.

HE DEVELOPMENT OF ADVANCED and more cost-effective industrial processes, driven mainly by the economy of scale and higher production rates, has boosted the presence of high-power (HP) drives in several industrial sectors. In addition, efficiency has become a major figure of merit in today's industry because of the economical benefits along with the importance of sustainability. This has led to a higher demand for adjustable speed drives (ASDs), increasing their percentage of share in a market greatly dominated by standard direct grid-connected motor drives

Doubly Excited Brushless Reluctance Machine (DEBRM) has gained much attention recently in the area of variable-speed constant-frequency generating systems and adjustable speed drives. Two types of reluctance rotor structure, axially laminated and simple salient rotors, are suggested in the DEBRM development. Due to the unconventional pole number combination of the stator and rotor, performance evaluation of the DEBRM with different rotor structures is difficult. A comparison study of two rotor structures of the DEBRM is presented in this paper by finite element analysis. It is shown that by calculating self-and mutual-flux linkage of the dual stator windings as the function of rotor positions, performance of the complicated' DEBRM can be evaluated conveniently. Various advantages and disadvantages of the DEBRM associated with the two rotor structures are also discussed.

The modern power systems are supplying an increasing number of non-linear loads like: double conversion systems, arc furnaces, arc discharging, high power cycloconverter (CCV) etc. These loads are harmonics and interharmonics sources. Therefore, it is important to measure interharmonics accurately. The Fast Fourier Transform (FFT) is used for signal processing because of its computational efficiency. Most power quality meters and

This paper deals with conducted electromagnetic interferences (EMIs) in adjustable-speed drive (ASD) systems. For some years, the use of high-speed switching power devices in ASDs induces high-voltage (dv/dt) and high-current (di/dt) variations that excite the parasitic elements of the power circuit, inducing conducted emissions. The advent of these devices has thus generated several unexpected problems, such as premature deterioration of motor ball bearings and high increases in the EMI levels, which are caused by the circulation of the high-frequency currents. In order to evaluate the level of the common-mode (CM) and the differential-mode (DM) currents in the ASD system, it is necessary to use a precise model of the pulse width modulation (PWM) inverter, power cable, and ac motor that takes into account various phenomena, which appear when the frequency increases. First, a PWM inverter and shielded four-wire power cable model are presented. Then, a new high-frequency modeling method of the ac motor is proposed. Finally, the ASD system is simulated and the obtained results are compared to the experimental measurements in the frequency and time domains.

The stator insulation breakdown is a major cause of AC machine failures. Ground insulation defaults are easily detected by classical systems based on leakage current measurements, however the turn-to-turn insulation degradations are more difficult to detect. For large machines, on-line methods, based on partial discharge detection and analysis, give good results but they cannot be used for low-voltage machines fed by adjustable speed drives (ASD). A new monitoring system able to detect slight variations of high frequency resonances in the winding of a working machine fed by an industrial inverter was presented in [1]. Several measurements can be used in order to estimate the aging of an AC machine winding (HF measurements of current or magnetic field) [2]. When a measure, also called a piece of information, is precise and certain, no other measure is necessary. However, such a measure is rarely obtained in real world application. Information fusion consists then in merging, or exploiting conjointly, several imperfect sources of information to make proper decision. Various frameworks can be used to model the fusion, e.g., probability theory, possibility theory, belief functions [3,4]. In this paper, different measurements of the aging of an AC machine winding are combined in the latter frame. This approach is tested on real measurements.

In this paper, the Direct Torque Control (DTC) for three-level five-phase inverter fed five-phase induction motor is proposed to improve the low speed performance. The classical DTC scheme (DTC-I) is modified in order to minimize the demagnetization effect during low speed operation. According to modification, the voltage vector space plane is divided into twenty sectors, each of sector 18º. For odd number of sectors, ±36º displaced intermediate voltage vectors and for even number of sectors, ±36º displaced main voltage vectors are selected instead of classic ±72º displaced voltage vectors. The zero voltage vectors are omitted in the proposed DTC scheme (DTC-II) for the low speed operation. The DTC-II scheme reduces the demagnetization effect during low speed region at the cost of increase in torque ripple due to avoiding zero voltage vectors. As the speed ramps up the ±72º displaced voltage vectors are selected through seven-level torque comparator and are divided in ten sectors. Therefore in the medium and the higher speed region the torque ripple are reduced by using seven-level torque comparator. Simulation and experimental results are presented in order to validate the DTC-II method.

Bearing voltages and associated bearing currents in electric machines driven by pulse width modulation (PWM) converters with high switching frequencies and high dv/dt can cause premature bearing failures. This paper proposes a new modeling approach for the prediction of steady-state and transient bearing voltages based on 2-dimensional (2D) electromagnetic finite element analysis (FEA) with coupled external circuits using measured bearing capacitance values. The distributed-element external circuit was employed mainly to take into account the influence of wire distribution and frequency dependency, which are typically neglected by traditional equivalent circuits. The developed model was then used to simulate bearing voltages for various scenarios and evaluate the effectiveness of several easy-to-implement bearing voltage reduction methods from the perspective of machine design and manufacturing, such as using the insulated shaft and/or bearings, introducing additional insulation in the rotor, and changing the material of machine components. Experimental measurements are also provided to facilitate the analysis and validate the proposed approach.

This paper presents a very simple off-line technique that is able to evaluate the aluminum electrolytic capacitors condition. The aging of these capacitors is expressed by the increase of their internal resistance that can reach twice the initial value at the end of life of the capacitor, while the capacitance can drop 20%. Thus, if both capacitance and internal resistance are quantified, it is possible to evaluate the capacitors condition. To do so, a very simple prototype consisting of a low frequency transformer, a DC power supply, a RC circuit and a digital oscilloscope connected to a computer can be used. Afterwards, by using the phase displacement between capacitor current and voltage, as well as the ratio between their modulus, it is possible to compute both resistance and capacitance of the capacitor under test. Several experimental results have been acquired in order to evaluate the applicability of the proposed technique.

This paper presents a scalar volt per hertz (V/f) control technique for maximum power tracking of a grid-connected wind-driven brushless doubly fed reluctance generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid and control winding, connected to the grid through a bi-directional converter. In order to enhance the performance of the proposed scalar-control strategy, a soft starting method is suggested to avoid the over-current of the bi-directional converter. Moreover, the capability of generator speed estimation for sensorless control is also studied. The capability of the proposed scalar-control technique is validated using a sample of simulation results. In addition, the presented simulation results ensure the effectiveness of the proposed control strategy for maximum wind-power extraction under windspeed variations. Furthermore, the results show that the estimated generator speed is in a good accordance with the actual generator speed which supports sensorless control capability.

A modulating signal (MS) applied to the control voltage has a profound effect on the DC and AC-side uncharacteristic harmonic currents. The presence of harmonic distortion in the AC-busbar voltage causes distortion on the DC-line current ripple. One reason for such distortion is the valve-asymmetrical firing pattern caused by the closed loop nature of constant current control. A second reason is that the DCcurrent ripple is related to AC-side harmonics even if no closed-loop current control is prescribed. A method of harmonic minimisation based on approximate linear relationships between uncharacteristic harmonics and the MS was developed and implemented on a convertor model. A circuit to select, adjust and inject the MS into the control voltage connected to the output of the injection circuit inhibits the MS injection during transients. This control feature is important because it allows fast transient response of the control and does not contribute to oscillatory behaviour. A full set of analytical predictions and model tests using the injection circuit described above for an MS of 50 Hz, 100 Hz and 150 Hz is presented. Control voltage modulation due to DC current ripple

Three-level neutral-point-clamped (NPC) inverters are very appropriate for high-power adjustable-speed drive applications. Direct torque control is characterized by the merits of fast response, simple structure and strong robustness to motor parameters variations. This paper presents a 3-level inverter-fed direct torque controlled (DTC) induction motor (IM) drive based on optimized switching table. The problems of high voltage jump, smooth vector switching and neutral point balance are investigated and solved by introducing appropriate intermediate vectors. Furthermore, a speed-adaptive flux observer is employed to enhance the performance of the system by estimating the state variables including the stator flux and state current. Large starting current, which can occur in conventional DTC drives, is controlled effectively by introducing pre-excitation of the stator flux. Both simulation and experimental results are presented to verify the effectiveness of the proposed schemes introduced in this paper. I.

The aim of the paper is to present a diagnostic system for shaft misalignment detection. The diagnostic system is used in an adjustable speed sensorless induction motor (IM) drive with an inverter output filter. A nonlinear control algorithm and state observer were used in the motor control. Because the inverter output filter was installed in the drive, the control structure, as well as the estimation systems, were adequately changed. The adaptive neuro-fuzzy inference system (ANFIS) is used for shaft coupling fault detection. ANFIS is based on the analysis of the stator current, motor speed, and load torque processing. ANFIS uses only signals estimated from the state observers whereas observers calculate required variables only on the base of the inverter input voltage and two output current sensors. No additional special sensors are required. The proposed diagnostic system clearly indicates the shaft misalignment. The paper presents the model of the drive, control and estimation algorithms, as well as the diagnostic system. Whole drive and ANFIS fault indicator were verified by experiments for a 1.5 kW induction motor drive system.

Subsea processing has been increasingly accepted by the offshore oil and gas industry as a solution to boost production and reduce cost. Accordingly, the subsea power demand is growing to support various processing loads, including pumps and compressors. Depending on the application, the power rating of a field ranges from tens of kilowatts to tens of megawatts, and the step-out distance ranges from a few kilometers to hundreds of kilometers. Considering the hostile and remote environment, a reliable subsea electrical-power system that is suitable for subsea deployment is clearly desired. This paper presents a modular direct-current electrical-power system that is designed for use in a subsea field with medium or long step-out distance. The proposed system consists of multiple modular converters in the subsea station to achieve the required power-conversion functions. It features high reliability, high flexibility, and reduced installation weight. The system operation and protection are presented, and the performance is verified by a laboratory-scale demonstration.

This paper describes the causes of voltage sags in industrial plants, their impacts on equipment operation, and possible solutions. The definition proposed focuses on system faults as the major cause of voltage sags. The sensitivity of different types of industrial equipment, including adjustable speed drive controls, programmable logic controllers, and motor contactors, is analyzed. Available methods of power conditioning for this sensitive equipment are also described.

This paper presents a scalar volt per hertz (V/f) control technique for maximum power tracking of a grid-connected wind-driven brushless doubly fed reluctance generator (BDFRG). The proposed generator has two stator windings namely; power winding, directly connected to the grid and control winding, connected to the grid through a bi-directional converter. In order to enhance the performance of the proposed scalar-control strategy, a soft starting method is suggested to avoid the over-current of the bi-directional converter. Moreover, the capability of generator speed estimation for sensorless control is also studied. The capability of the proposed scalar-control technique is validated using a sample of simulation results. In addition, the presented simulation results ensure the effectiveness of the proposed control strategy for maximum wind-power extraction under windspeed variations. Furthermore, the results show that the estimated generator speed is in a good accordance with the actual generator speed which supports sensorless control capability.

This paper deals with conducted electromagnetic interferences (EMIs) in adjustable-speed drive (ASD) systems. For some years, the use of high-speed switching power devices in ASDs induces high-voltage (dv/dt) and high-current (di/dt) variations that excite the parasitic elements of the power circuit, inducing conducted emissions. The advent of these devices has thus generated several unexpected problems, such as premature deterioration of motor ball bearings and high increases in the EMI levels, which are caused by the circulation of the high-frequency currents. In order to evaluate the level of the common-mode (CM) and the differential-mode (DM) currents in the ASD system, it is necessary to use a precise model of the pulse width modulation (PWM) inverter, power cable, and ac motor that takes into account various phenomena, which appear when the frequency increases. First, a PWM inverter and shielded four-wire power cable model are presented. Then, a new high-frequency modeling method of the ac motor is proposed. Finally, the ASD system is simulated and the obtained results are compared to the experimental measurements in the frequency and time domains.

The interest in energy conservation has focused attention on adjustable speed electrical drives for loads traditionally driven by single speed motors with mechanical methods of load modulation. With large motor ratings, starting systems to reduce the impact on the power supply system are increasing in interest. Large size (above 2000 hp) adjustable frequency synchronous motor systems, called varichron drives for simplicity, are discussed. These drives are totally soft start systems and have the highest operating efficiency available. Eight major considerations which must be addressed in the application of these drives in industry are outlined and described.

Drive train bench, which is a type of dynamometer, is used to test the power train components of a vehicle such as transmission, torque converter, etc. The test system has to simulate the vibration torque of the engine by motor control. Conventionally, a sine wave is used to simulate the vibration torque of an engine. However, the actual vibration torque waveform contains harmonic distortion components inherent in the engine. Therefore, it is desirable to have a vibration control technique capable of simulating the waveform of the engine torque more accurately. This paper proposes a novel engine torque simulated vibration control for the drive train bench system. The proposed method can achieve a shaft torque detection value that follows the desired engine pulsation torque waveform by utilizing robust resonance suppression control and a generalized periodic disturbance observer. The validity and usefulness of this technology are indicated by the theoretical explanation, simulation, and experimental results.

In the last few years, new efficiency requirements for induction motors have been imposed. Therefore electrical machines manufacturers have had to redefine the design criteria in order to reduce losses aiming to achieve the efficiency values established by the IE2 and IE3 standard categories according to the IEC. Given that, in the near future, an increasing demand regarding efficiency (IE4 and IE5 categories) is expected, it would be appropriate to seek new alternatives to further reduce losses in induction motors. In this work, the possibility to use magnetic wedges in induction motors with semi-closed slots is studied. This strategy allows to reduce copper and core losses, therefore increasing then the motor efficiency. The study analyses low power motors and considers different permeabilities and geometries for the magnetic wedges. In addition, it focuses attention on the starting torque and currents. Finally, an experimental validation using a 3-kW 380-V 4-pole IE2-class induction motor is presented.

A methodology for steady-state performance analysis and design of the doubly fed reluctance motor (DFRM) is presented in this paper. Emphasis is placed on the linear model of the DFRM, but magnetic nonlinearities are also characterized. A prototype 2-hp DFRM is designed and built in comparison with an induction motor. Performance of the prototype 2-hp DFRM motor is analyzed thoroughly and is supported by actual measurements, wherever available.

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