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Induction motors (IMs) are one of the most widely used motor types in the industry due to their low cost, high reliability, and efficiency. Nevertheless, like other types of AC motors, they are prone to various faults. In this article, a low-cost embedded system based on a microcontroller with the ARM Cortex-M4 core is proposed for the extraction of stator winding faults (interturn short circuits) and an unbalanced supply voltage of the induction motor drive. The voltage induced in the measurement coil by the axial flux was used as a source of diagnostic information. The process of signal measurement, acquisition, and processing using a cost-optimized embedded system (NUCLEO-L476RG), with the potential for industrial deployment, is described in detail. In addition, the analysis of the possibility of distinguishing between interturn short circuits and unbalanced supply voltage was carried out. The effect of motor operating conditions and fault severity on the symptom extraction process was also studied. The results of the experimental research conducted on a 1.5 kW IM confirmed the effectiveness of the developed embedded system in the extraction of these types of faults. [ABSTRACT FROM AUTHOR]

To solve the problems mechanically caused by parallel direct‐drive permanent magnet motors (DD‐PMSM). This paper proposes a concave‐core stator direct‐drive permanent magnet motor (CCSDD‐PMSM) structure. In this study, an auxiliary yoke structure is proposed to optimise the magnetic circuit and analyse the cogging torque to achieve the minimum detent force. Based on the unit motor and combined with the magnetomotive force to analyse the symmetry of different winding distributions, the stability characteristics of the motor are studied. The magnetic field distribution of the motor load air gap is calculated using the finite element method. The contribution of different spatial order harmonics to the motor output torque is calculated using the Maxwell tensor method. The torque calculation expression of the CCSDD‐PMSM is given. Finally, an experimental prototype is made to verify the accuracy of the analysis in this paper. [ABSTRACT FROM AUTHOR]

In this paper, an extended-horizon predictive torque control (PTC) method is proposed with computationally efficient implementation. Predictive control with extended horizon brings important advantages compared to single-horizon methods, such as better steady-state performance, reduced current THD, and lower ripples in torque and stator flux. However, the computational burden is a serious obstacle because the required calculations rise exponentially with the extension of the prediction horizon. This is due to a high number of candidate voltage vectors and also predicting the values of several machine variables for these vectors. Different approaches are employed in this work to make the control method computationally tractable. A voltage vector reduction technique is utilised that significantly decreases the total number of enumerated vectors. Moreover, the stator current prediction is eliminated in the proposed method, based on the inherent features of the PMSM. The proposed method is experimentally implemented and its good performance and advantages are verified. [ABSTRACT FROM AUTHOR]

Discrete space vector modulation (DSVM) is employed to synthesize large number of voltage vectors (VVs) to improve the steady-state performance of predictive torque control (PTC). However, enumerating all the VVs in the prediction process increases the computation load of the motor drive. To address this issue, this article proposes a unidirectional VV preselection (UVVP) method for optimizing the performance of DSVM-based PTC of ac motors. The proposed UVVP method divides both voltage space vector diagram (VSVD) and flux space trajectory into twelve 30° based sectors to reduce the impact of candidate VVs with negative effects. At each flux position, the UVVP strategy can restrict the nearest candidate VVs in the 30° based VSVD region within the circular flux trajectory. This is achieved by using the speed direction to avoid the candidate VVs, which are in the same flux sector for reverse flux rotation, hence resulting in significant flux and torque ripple reduction. The main benefit of the proposed method is its simplicity since it only requires the flux sector and speed information as well as it can generate the VV enumerations online while ensuring the reduction of computation burden. [ABSTRACT FROM AUTHOR]

Unavoidably, the controlsystem of any permanent magnet synchronous motor (PMSM) is subjected to perturbations, e.g., motor nonidealities and inverter nonlinearities. To reject these perturbations, a new super-twisting (ST) control variant, called speed adaptive super-twisting (S-AST) control, is proposed in this paper. In the S-AST control, a proportional-integral (PI) and a ST controllers are merged using an adaptive law that is based on the motor speed measurement. This is done to reduce the chattering problems that the standard ST control presents. In addition, a mathematical design for the S-AST control is proposed, where the relationship between the chattering amplitude, the switching frequency and the system perturbations is shown. The main contribution in this paper is the application of the S-AST controller to reduce the total harmonic distortion (THDi) of the PMSM currents. By comparing the S-AST control against PI control, the THDi is reduced from 9.9% to 1.27%, in simulation, and the THDi is reduced from 22.79% to 1.56%, experimentally. These results demonstrate how the S-AST control is an excellent alternative to improve the waveform of the PMSM currents. [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]

This letter addresses experimental validation of the reduced-order natural speed observer design for position sensorless drive with nonsalient permanent magnet synchronous motor. The natural speed observer and the active flux estimator are connected in a cascaded fashion, which results in a simple sensorless algorithm that needs only to tune one bandwidth parameter for flux estimation and one bandwidth parameter for speed observation. Experimental results of high speed reversal test, zero speed stopping test, and slow speed reversal test are included, where the practice of applying nonzero $d$ -axis current at zero speed has shown to be effective for loaded zero speed stopping test, but it causes zero-speed locked-up at slow speed reversal with acceleration rate of $\rm \text{50}\,r/\text{min}/s$. Four remedies are compared to improve the slow speed reversal test and the proposed method gives almost ramp actual speed waveform, nondiverging $q$ -axis current and smooth transition in position waveform during slow zero speed crossing. A new dynamic expression of the active flux is proposed and with the aid of the active flux concept, the proposed sensorless algorithm is also applicable to various types of ac motors. [ABSTRACT FROM AUTHOR]

This article proposes an offline compensation method for current scaling gains in the AC motor drive systems with three-phase current sensors. Many articles have been presented about the current scaling gain compensations of inverters. Most of them can be adopted during rotations. Those were studied for two-phase current sensing. Applications, such as elevators and hoist cranes, generally measure three-phase currents directly using three current sensors in preparation for a fault in any one of them. In this article, we present a compensation method for a three-phase current sensing system. This article analyzes the effect of current scaling gain errors on the neutral current that is calculated with measured stator currents. Based on the analysis, a compensation strategy for the current scaling gains is presented. The proposed method is applicable only at a standstill. It can be used for initial commissioning since it works at a standstill regardless of whether the rotor is locked or not. The experiments that demonstrate the validity of the proposed method were carried out in an elevator system as well as a laboratory. The proposed method is simple to be implemented and it requires no additional hardware. [ABSTRACT FROM AUTHOR]

This two-part article compares the torque performance of 12 types of ac machines based on the same surface current density, tooth flux density, and rotor dimensions. Part II examines the torque capability of machines more recently developed which utilize the wave shaping capability of a solid-state frequency inverter. Essen's equation, as utilized in Part II, is modified to accommodate machines requiring non-sinusoidal waveforms. The “tau” factor, introduced in Part I, is also modified and is again used as means for comparison of any ac machine with an “ideal” machine based now upon a modified form of Essen's equation. [ABSTRACT FROM AUTHOR]

Hybrid electric propulsion could be the solution to the ambitious environmental targets of the aerospace industry. Fully-superconducting machines have the potential to deliver the step-change in specific torque, power, and efficiency capabilities required for large civil transport aircraft applications. However, fully-superconducting machines are still in their infancy. This article investigates the electromagnetic design of two different stator design concepts for an ac fully-superconducting machine for an aerospace distributed fan motor application. A benchmark aerospace specification of 1 MW was chosen and the design of a conventional permanent-magnet machine was used to assess the performance of the two equivalent fully-superconducting ac motor designs. Following the guidelines from an experimental study of the losses in a small ac stator prototype with MgB2 coils, a fully-superconducting air-cored stator design and a new yokeless stator design are proposed. Both ac superconducting machine designs use superconducting bulk magnets mounted on a rotor core and an MgB2 superconducting stator winding. This article discusses the key design issues of the two stator layouts in relation to the current aerospace targets for efficiency and power density. [ABSTRACT FROM AUTHOR]

This article proposes a new predictive current control (PCC) strategy for a dual-inverter fed four-level (4-L) open-end winding induction motor drive (OEWIMD). The individual inverters of the dual-inverter system are operated with dc-link voltages, which are in the ratio of 2:1. In general, the PCC for the 4-L OEWIMD requires the evaluation of all of the 37 available voltage vectors (VVs) to select the optimal one. An improvised PCC is proposed in this article, wherein the inverter with lower dc-input voltage is clamped, while the other inverter is switched around it. An important feature of the proposed PCC is that it evaluates only five candidate VVs to determine the optimal vector. The simulation and the experimental results reveal that the performance of the proposed PCC technique is superior to the conventional PCC in terms of voltage and current total harmonic distortion (THD), torque-ripple, and total drive loss. Furthermore, the proposed PCC results in the reduction of the computational burden on the controller. Also, as the reduction of switching frequency is inherent in the proposed PCC strategy, there is no requirement to add an additional constraint to reduce it in the cost function. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) has been identified as one of the root causes of stator insulation failure even for low voltage (LV) ac motors. For reliable operation of variable frequency drive motors, a standard acceptance test procedure (IEC STD 60034-18-41) to ensure PD-free operation of LV motors was developed. Although the test can verify whether PD exists in the stator for a surge with predetermined voltage level and risetime, the information on where PD activity is present in the stator insulation is not provided. In this article, a test method based on a new variable risetime surge generator is proposed for identifying the component of stator insulation where PD occurs in LV random wound stators. The proposed test allows the user to locate whether PD is in the turn, phase, or ground insulation. This information is critical for lowering the PD inception voltage for improving the motor reliability through insulation system design/manufacturing or motor/drive system reconfiguration. The test is implemented with a 4.5 kV variable risetime surge generator prototype, and seven LV ac motors are tested to show where PD is likely to occur in commercial LV motors. [ABSTRACT FROM AUTHOR]

The paper describes manufacturing and testing of HTS double racetrack coils intended for use in stator windings of small-size motor, proposed for electric unmanned air vehicle (UAV). The level of AC losses of the armature characterizes required flow of liquid hydrogen (LH) coolant. Thus, it affects overall configuration of the UAV by LH-tank mass and volume. On the other side, motor will be driven by AC motor controller (inverter), so the armature currents will not be pure sinusoidal, and formed by pulse width modulation (PWM). In this work, the manufactured coil is tested on meander-form AC current with frequencies up to 200 Hz with and without solid ferromagnetic core. In addition, losses on PWM currents were also determined on a specific H-bridge to ensure functionality of HTS coils in such conditions. [ABSTRACT FROM AUTHOR]

In this article, a new online continuous control set-predictive controller (CCS-PC) is proposed with the objective of minimizing the stator-flux and torque ripples. In this controller, a constrained optimization problem is constructed to optimize the phase, amplitude, and time duration of the voltage vector applied to the motor. Fast Iterative Shrinkage-Thresholding Algorithm (FISTA) which is an advanced algorithm based on fast proximal gradient method is adopted to find the optimal solution in an online manner. In each control period, FISTA is executed 10 times where the voltage vector found in the last iteration is considered as the optimal voltage vector. Performance of the proposed controller is compared with the performance of an offline CCS-PC through various experiments. In these experiments, stator-flux ripple, torque ripple, stator-current total harmonic distortion, and computational complexity of the controllers are compared with each other. Based on the results, pros and cons of the proposed online CCS-PC are highlighted. [ABSTRACT FROM AUTHOR]

This article investigates a novel two-converter-based operation of a brushless doubly fed reluctance machine (BDFRM). The BDFRM has a ducted rotor, and the stator is wound with two distributed windings, which are fed from two separate power converters. Operation theory with frequency sharing between the two windings is introduced. The prototype BDFRM design, machine assembly, and the corresponding motor drive implementation processes are discussed. The control strategy for frequency sharing mode of operation with two variable winding frequencies is discussed. Subsequently, the BDFRM drive is tested in frequency sharing mode at varying speed levels and loads. [ABSTRACT FROM AUTHOR]

The use of fast wide-bandgap devices in high-speed electrical drives with steep pulsewidth modulation voltage waveforms is the main cause of increased stress on the electric machine insulation system and consequently, of reduced reliability of the whole system. This represents a major concern in safety-critical applications, such as in the aerospace and electric transportation fields. The novel contribution of this work is to assess the effects of electrical aging on complex insulation systems (i.e., a whole stator winding) by analyzing easily measurable macroscopic quantities. To this purpose, an electrical aging procedure is defined, and the effects produced on three tested motors are presented. Three different analysis methods are adopted with the aim of assessing the damage caused to an ac motor winding by such steep voltage waveforms and hence to evaluate the state of aging of the insulation system. [ABSTRACT FROM AUTHOR]

This paper offers methods to analyze the performance of three-phase synchronous machines operating with an unsymmetrical stator winding caused by cutting out and bypassing coils. The resulting unsymmetrical current distribution in the stator winding tends to produce overheating in parts of the stator and damper windings at full load as well as torque pulsations. Thus, the main objective of this study is to determine the maximal load, under which the unsymmetrical machine may operate without exceeding the permissible temperature limit. Based on the multiloop method, a mathematical model of a synchronous machine with missing coils in the stator winding is developed. In order to determine the current distribution, the machines’ system of differential equations is solved by using a numerical integration method (Runge–Kutta method). As an alternative method, the system of differential equations in the steady state is reduced to a system of algebraic equations, which can be solved with the Gaussian elimination method. Both methods are validated by the measurement results of a 25-kW salient pole synchronous machine. Furthermore, both the circulating current within the parallel branches and the line currents of the different phases as a result of coil or coil group cut-outs are analyzed for a large 41-MW cylindrical rotor synchronous motor. [ABSTRACT FROM AUTHOR]

In this paper, an improved predictive torque control without weighting factor is proposed for a voltage source inverter-permanent magnet synchronous motor drive system, which possesses good control performance of torque and stator flux. By investigating the relationship among torque, the reference stator flux amplitude, and the phase angle of the stator flux, the reference stator flux vector is constructed. Then, the reference voltage vector is calculated by the reference stator flux vector based on the delay compensation and the deadbeat control. The extended control set is designed and two generalized base vectors that require further screening are determined based on the position of the reference voltage vector to improve the calculation efficiency. And the duty ratios used for the generalized base vectors are calculated, according to the geometric relations between the generalized base vectors and the reference voltage vector. Finally, by the duty cycle control between two generalized base vectors and between each generalized base vector and zero vector, the candidate vectors are gained and substituted into the cost function only with the flux vector error term. Experiment tests were carried out and the results validated the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The reliability of medium voltage (MV) motors used for driving pumps, fans, and other loads in the power generation industry is critical for continued power production. Periodic testing of stator winding insulation, which is the most vulnerable component in MV motors, is an essential part of predictive maintenance for preventing unplanned reduction in the power generation capability. Korea Electric Power Corporation (KEPCO) Research Institute's 17+ years of experience on predictive maintenance of stator insulation for MV motors is presented in this paper. KEPCO's stator insulation test program and statistics of test records are summarized, and cases of recent turn and phase insulation failures that resulted in motor forced outages are investigated. Analysis of the turn or phase insulation failures and insulation test records performed on the failed motors show that it is difficult to predict turn or phase insulation failures with the insulation tests currently performed. Turn or phase insulation test methods are summarized and evaluated based on the findings of the investigation to help target future research efforts toward industrial needs. [ABSTRACT FROM PUBLISHER]

A single or three phase asynchronous motors, or known a squirrel cage motors (SCMs) are represent one of generally using in many industrial applications. They are consuming further than half-percent of the total generated electrical energy. This motor is working at its full speed when it is attached to the main AC- supply. Therefore, speed control of asynchronous motor is necessary to industrial applications that require changeable flow control of fluid (air, water and chemical liquid streaming). There are many methods to control the speed of motors, such as changing the stator number of poles, controlling supply voltage, addition series reactor or resistances. The modern method is Volt per Hertz, or scalar control this method applied by changing voltage and frequency of three-phase supply, or by making a V/f equal to a constant value in this method a large amount of energy can be saved. In this study, analysis and practical implemented to variable voltage Variable Frequency Drive or called a VFD. The model enables an exception of a large amount of energy, when connected to control speed of Induction motor. A new simplified method for implemented of an AC Drive system with a moderate price for components was proposed. This method totally based on assembling overall components of AC-Drive. The advantage of this design is simplicity, robustness and ease of tuning as well as manufacturing due to these advantages. This design is very suitable for real time applications as motor speed controller. The experimental results obtained show that design helps to preserve a large amount of energy to the power grid, by a limited starting current of the motor as well, eliminating a voltage flicker at starting and reducing dissipating power during running in long period. Results verified experimentally [ABSTRACT FROM AUTHOR]

In the recent years, the use of model predictive control in electrical drives has been widely reported both theoretically and experimentally. Predictive torque control has been developed to control induction motor drives, allowing high performance and fast dynamics. However, the optimization used in predictive torque control is based on a single cost function minimization, where control objectives are merged by using weighting factors. The selection of these scalar factors is achieved through offline and online search methods and they are heavily dependent on the system parameters. To avoid this drawback, a multiobjective fuzzy predictive torque control is presented. The proposed strategy replaces the minimization of a scalar cost function with a multiobjective optimization using fuzzy decision making. Experimental implementation is presented to validate the performance of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper presents an approach to the thermal design of an ac machine where the application requires low-duty transient operation. To provide accurate temperature predictions, the design process has been informed with experimental data from tests on a stator-winding sector (motorette). These have been shown to be a time and cost-effective means of calibrating the thermal model of a full machine assembly, prior to manufacture of the final design. Such an approach is usually adopted in design analysis of machines with a concentrated winding topology. Here, the motorette testing has been extended to a machine with a distributed winding. Several alternate slot liner and impregnating materials have been evaluated to maximize the heat transfer from the winding body into the machine periphery, and a total of nine stator section samples have been manufactured and tested. The performance tradeoffs between the various combinations are discussed in detail alongside their ability to satisfy the design requirements. Based upon these experimental results, the most promising designs have been selected for transient duty analysis against the design specification. A lumped parameter thermal model has been used for this purpose and calibrated using the data from the subassembly testing. Experimental results on the full machine assembly are presented, showing good correlation with the motorette calibrated thermal model. [ABSTRACT FROM AUTHOR]

After designing and optimizing an electric machine, efficiency maps are needed to predict a vehicle’s performance in a dynamic simulation. Calculating efficiencies at various torque and speed points, however, requires prior knowledge of the input excitation conditions, such as the current magnitude and advance angle, in an electromagnetic finite-element analysis simulation. Hence, this paper derives and uses nonlinear motor control equations (MTPA, FW, MTPV) in the study of efficiency map calculation while accounting for both saturation and cross-coupling effects. Two synchronous ac motors are considered in this paper, including the 2010 Prius IPM and a PM-assisted synchronous reluctance machine, with all procedure steps outlined in detail. [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]

The fault detection of electrical or mechanical anomalies in induction motors has been a challenging problem for researchers over decades to ensure the safety and economic operations of industrial processes. To address this issue, this paper studies the stator current data obtained from inverter-fed laboratory induction motors and investigates the unique signatures of the healthy and faulty motors with the aim of developing knowledge based fault detection method for performing online detection of motor fault problems, such as broken-rotor-bar and bearing faults. Stator current data collected from induction motors were analyzed by leveraging fast Fourier transform (FFT), and the FFT results were further analyzed by the independent component analysis (ICA) method to obtain independent components and signature features that are referred to as FFT-ICA features of stator currents. The resulting FFT-ICA features contain rich information on the signatures of the healthy and faulty motors, which are further analyzed to build a feature knowledge database for online fault detection. Through case studies, this paper demonstrated the high accuracy, simplicity, and robustness of the proposed fault detection scheme for fault detection of induction motors. In addition, with the integration of the feature knowledge database, prior knowledge of the motor parameters, such as rotor speed and per-unit slip, which are needed by the other motor current signature analysis (MCSA) methods, is not required for the proposed method, which makes it more efficient compared with the other MCSA methods. [ABSTRACT FROM PUBLISHER]

Alternating-current motor drive systems consume the majority of global electricity, but most of them are still not efficient enough. This paper proposes a complete solution to the efficiency enhancement of general induction motor (IM) drive systems with the least cost and a high reliability. On the motor side, the squirrel-cage rotors of IMs are replaced with optimally designed interior permanent-magnet (PM) rotors without damping windings; meanwhile, other assemblies remained unchanged. Stators with both wye- and delta-connected windings are investigated, and super premium efficiency (IE4) is achieved on all the remanufactured motors in this paper. On the drive side, the maximum efficiency per ampere algorithm is realized based on the position-sensorless control to better exert the motor efficiency and reduce the system cost. For applications where an original IM is used under a grid drive, this paper safely switches the remanufactured interior PM synchronous motors from an inverter to the grid drive. A total of seven prototypes with different rated powers and velocities are remanufactured, and various experiments are provided as the verifications of the effectiveness and practicability of the proposed solution. [ABSTRACT FROM PUBLISHER]

The performance of a speed-sensorless induction motor drive is poor at low-speed range. This is because the inverter nonlinear error, such as inaccurate motor parameters, deadtime, turn on/off delay, and on-state voltage drop of power switches, has strong influence on the speed estimation at low-speed range. In this paper, the feedback gains of an adaptive full-order observer are designed to guarantee the stability of speed estimation and to reduce the influence of the inverter nonlinear error on the speed estimation. In addition, the estimated current error caused by the inverter nonlinear error is identified offline. It is stored in the lookup table to compensate for the influence of the inverter nonlinear error on the speed estimation. The feasibility of the proposed method is verified by experiments. [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]

In this paper, an investigation into an alternative topology for reluctance synchronous machine rotor flux barriers is presented. The investigated topology employs a high number of flux barrier variables with an alternative asymmetric rotor structure. The focus in this paper is on maximizing average torque and minimizing torque ripple, using finite element-based design optimization, in order to study the possibility of achieving acceptably low torque ripple. A subsequent investigation into the effect of rotor skew on the proposed optimized design to reduce torque ripple even further is also conducted, as well as the manufacturing and testing of the proposed flux barrier prototype. [ABSTRACT FROM PUBLISHER]

Insulation failures are one of the most common failure modes of ac motors, particularly high-voltage motors. Online monitoring of insulation health of ac motors is important for preventing unexpected outages and minimizing the associated financial losses, particularly in critical applications. Previously, an online ground-wall insulation monitoring technique has already been proposed for six-lead ac motors. In this paper, a novel online ground-wall insulation monitoring scheme is proposed for inverter-fed ac motors. This approach is based on measurement of common-mode insulation leakage current for online capacitance and dissipation factor (C/DF) monitoring. The proposed technique can be applied to both three-lead and six-lead ac motors and can also be extended to monitor the insulation health of the cable connecting the inverter and the motor. The proposed technique is demonstrated in the lab environment and correlated with standard offline C/DF measurements. [ABSTRACT FROM AUTHOR]

Early detection of faults in electrical machines, particularly in induction motors, has become necessary and critical in reducing costs by avoiding unexpected and unnecessary maintenance and outages in industrial applications. Additionally, most of these faults are due to problems in bearings. Thus, in this paper, experimental bearing fault detection of a three-phase induction motor is performed by analyzing the squared envelope spectrum of the stator current. Spectral kurtosis-based algorithms, namely, the fast kurtogram and the wavelet kurtogram, are also applied to improve the envelope analysis. Experimental tests are performed, considering outer bearing faults at different stages, and the results are promising. [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]

This paper explores the design, online, of an electrical machine's healthy reference by means of statistical tools. The definition of a healthy reference enables the computation of normalized fault indicators whose value is independent of the system's characteristics. This is a great advantage when diagnosing a broad range of systems with different power, coupling, inertia, load, etc. In this paper, an original method called spectral kurtosis with reference is presented to design a system's healthy reference. Its principle is first explained on a synthetic signal. This approach is then evaluated for mechanical unbalance detection in an induction machine using the stator current instantaneous frequency. The normalized behavior of the proposed indicator is then confirmed for different operating conditions, and its robustness with respect to load variations is demonstrated. Finally, the advantages of using a statistical indicator based on a healthy reference compared with a raw fault signature are discussed. [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]

To avoid inconvenience caused by shaft rotation and improve immunity to measurement noises, an elaborately designed scheme is proposed for parameter identification of induction motors. After analyzing the responses of a simple step-voltage test, a sequence of pseudorandom signals, customized to excite abundant dynamics in the featured frequency band of the motor, are injected into the stator in a single-phase mode at standstill. The crucial feature of the proposed scheme is that a nonlinear procedure is introduced to minimize “predicted errors” of the estimation model, which lowers influences of measurement noises notably, and thus the design of low-pass filters is simplified greatly. Experimental comparisons are carried out, including not only tests on a squirrel-cage motor, but also extended tests on a wound-rotor motor to testify accuracy of rotor-side parameters, both using a real inverter. The results indicate that the proposed scheme is able to estimate parameters required by controllers accurately in the noisy environment, and improve performances of sensorless motor drivers. [ABSTRACT FROM AUTHOR]

The control algorithms of electrical machine drives rely on models that are classically valid for signals in low-frequency ranges versus the current sampling frequency and the range of eddy currents. Some position self-sensing methods, which are used in motion-sensorless controls, are based on the injection of high-frequency signals, for which the model needs to be refined, taking the discretization and the eddy-current effects into account. In this paper, we introduce different circuit models for ac permanent-magnet machines, which are valid from low- to high-frequency spectra, for the purpose of analysis. Combined with the identification of two experimental machines, the goal is to highlight some conclusions about the suitable frequencies for self-sensing. [ABSTRACT FROM PUBLISHER]

The canned induction motors are widely used in pharmaceutical, chemical, and nuclear fields. It is necessary to calculate the losses, particularly the can losses, accurately. Combining steady-state ac magnetic 2-D finite-element solutions with the can harmonic loss formulas derived in this paper, the can losses under rated voltage in various operating conditions are obtained. Then, the calculation results under various voltages in no-load condition are compared with the experiment data, which provides the basis for the further performance analysis and motor design. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A new methodology for diagnosing the stator winding faults in the six-phase induction motor. [•] The methodology uses the xy current trajectory mass center. [•] A theoretical analysis of the six-phase motor healthy and stator fault operation modes. [•] Results are presented to show the applicability of the proposed technique. [Copyright &y& Elsevier]

The rotor position is required in many control schemes in electrical drives. Replacing position sensors by machine self-sensing estimators increases reliability and reduces cost. Solutions based on tracking magnetic anisotropies through the monitoring of the incremental inductance variations are efficient at low-speed and standstill operations. This inductance can be estimated by measuring the response to the injection of high-frequency signals. In general, however, the selection of the optimal frequency is not addressed thoroughly. In this paper, we propose discrete-time operations based on a rotating voltage injection at frequencies up to one-third of the sampling frequency used by the digital controller. The impact on the rotation drive, the computational requirement, the robustness, and the effect of the resistance on the position estimation are analyzed regarding the signal frequency. [ABSTRACT FROM PUBLISHER]

Phase-resolved partial discharge patterns of an inter-turn insulation specimen for a stator winding are investigated at different aging times under continuous square-wave pulse voltage. Comparing phase-resolved partial discharge patterns after square-wave pulse-voltage aging to those after sinusoidal-voltage aging, obvious independent clusters of discharge numbers occur with increases in the aging time of pulse voltage, whereas no similar phenomenon is observed after sinusoidal-voltage aging. Based on detailed analysis, partial discharge activity in a larger void is more intense, because the larger void has a larger memory effect, which is related to the number of residual charges. The enhanced electric field of the larger void accelerates the increase in void size. Furthermore, when the phase-resolved partial discharge patterns are measured under 50 Hz of sinusoidal voltage, since sinusoidal voltage creates less memory effect due to less residual charges, the corresponding partial discharges of different-sized voids occur at distinctly different phases of the sinusoidal voltage. For this reason, the independent clusters occur and become obvious with pulse-voltage aging. As a result, for pulse-width-modulated motors in industry, it is possible to evaluate the insulation condition through phase-resolved partial discharge patterns using 50 Hz partial discharge measurement. [ABSTRACT FROM AUTHOR]

Fault-tolerant control (FTC) solutions are increasingly being used in modern drive systems with AC motors. Such systems provide a higher degree of security and solutions that allow the on-line detection and localization of failures, as well as the switching of the control mode to a mode that allows us to continue the operation or safely stop the drive system. As the current sensors (CSs) are necessary to ensure precise control of the AC motors, in the event of their failure, one of two strategies can be used—hardware or software redundancy. The first strategy requires the use of additional measuring sensors. For this reason, the algorithmic solution, based on the Luenberger Observer (LO), has been proposed in this article as one of the software redundancy methods. In contrast to methods presented in the literature, the proposed solution allows one not only to compensate the stator current in a phase with a faulty CS, but also to adjust the correction of current estimation based on a measured signal in the other phase with a healthy CS. Extensive simulation studies in the direct rotor flux-oriented control (DRFOC) structure with the induction motor (IM) confirm the effectiveness of the proposed method. In addition, the proposed solution allows the drive system to be controlled even if all CSs are damaged. [ABSTRACT FROM AUTHOR]

In this paper, a sensorless method for low- and zero-speed operations is proposed for a high-power medium-voltage pulsewidth-modulated current-source-converter-fed interior-permanent-magnet motor drive system. The proposed method is based on the injection of a high frequency (HF) pulsating sinusoidal signal in the estimated synchronous reference frame of the drive's field-oriented control (FOC) scheme. The conventional FOC control scheme, low switching frequency, dc-link inductor, and the inverter output three-phase filter capacitor of the medium-voltage high-power current-source drive present some challenges in the generation and design of the HF-injection signal. To overcome these challenges, the FOC scheme is modified by introducing a modulation index control with suitable dc-link current compensation to enhance the dynamic response of the injected signal and prevent any clamp in the injected signal. In addition, a multisampling-space-vector-modulation method is proposed to prevent the distortion in the HF signal due to a low switching frequency to injected signal ratio. A detailed study and analysis regarding the influence of low switching frequency, output filter capacitor, and magnetic saturation in the injection method is carried out to determine the visible HF range of the injected signal. It is found that, by using the proposed FOC scheme and multisampling modulation scheme and by the proper design of the HF signal, an accurate rotor flux angle can be estimated for sensorless zero-/low-speed operations. Experimental results are provided to verify the proposed control method. [ABSTRACT FROM PUBLISHER]

This paper presents the measured experimental results from a four-pole toroidally wound induction machine, where the stator is constructed as a prewound foldable strip. It shows that if the machine is axially restricted in length, the toroidally wound induction machine can have substantially shorter stator end windings than conventionally wound induction machines, and hence, it shows that a toroidally wound induction machine can have lower losses and a higher efficiency. This paper also presents the employed construction method, which emphasizes manufacturability, and highlights the advantages and disadvantages of this method. [ABSTRACT FROM PUBLISHER]

This paper proposes a sensorless speed control strategy for a permanent-magnet synchronous motor (PMSM) based on a new sliding-mode observer (SMO), which substitutes a sigmoid function for the signum function with a variable boundary layer. In order to apply a sensorless PMSM control which is robust against parameter fluctuations and disturbances, a high-speed SMO is proposed, which estimates the rotor position and the angular velocity from the back EMF. In the conventional SMO, a low-pass filter and an additional position compensation of the rotor are used to reduce the chattering problem that is commonly found in the SMO using the signum function. In order to overcome the time delay caused by the low-pass filter, in this research, a sigmoid function is used for the switching function instead of the signum function. Also, the variation in the stator resistance is estimated to improve the steady-state performance of the SMO. The stability of the proposed SMO was verified using the Lyapunov second method to determine the observer gain. The validity of the proposed high-speed PMSM sensorless velocity control has been demonstrated with simulations and real experiments. [ABSTRACT FROM AUTHOR]

This paper presents a neural approach to detect and locate automatically an interturn short-circuit fault in the stator windings of the induction machine. The fault detection and location are achieved by .a feedforward multilayer-perceptron neural network (NN) trained by back propagation. The location process is based on monitoring the three-phase shifts between the line current and the phase voltage of the machine. The required data for training and testing the NN are experimentally generated from a three-phase induction motor with different interturn short-circuit faults. Simulation, as well as experimental, results are presented in this paper to demonstrate the effectiveness of the used method. [ABSTRACT FROM AUTHOR]

This paper proposes a remote and sensorless stator winding resistance estimation method for thermal protection of soft-starter-connected induction motors. By changing the gate drive signals of the thyristors in the soft starter, a small adjustable dc bias can be intermittently injected to the motor for the estimation of the stator winding resistance. Based on online and continuous monitoring of the stator winding resistance, the stator winding temperature can be monitored using only motor voltage and current. In addition, the torque pulsation caused by the injected dc bias is analyzed. It can also be controlled under an acceptable level by adjusting the level of the injected dc signal. The influence of cable resistance is also studied, and a compensation method is proposed. The proposed method has been verified by experimental results from two induction motors. The proposed stator resistance estimation method can provide remote, sensorless, and accurate thermal protection for soft-starter-connected induction motors. [ABSTRACT FROM AUTHOR]

A literature survey reveals that the study of rotational power losses in stator cores has been conventionally performed by means of finite-element analysis. This paper proposes an alternative characterization of rotational power losses in the tooth roots—a region that has been long known as a seat of flux rotation—relating some geometric dimensions to the values of flux density of interest to compute the rotational losses over the region. A simplified computation of maximum and minimum flux densities is proposed based on the trajectories of flux at singular time intervals. This enables the calculation using analytical expressions. For that reason, the proposed approach improves the power losses analysis in early design stages, showing the impact of projected geometries on the total loss estimate. Moreover, it consequently provides a tool to include the rotational losses estimate within optimization-oriented iterative searches. [ABSTRACT FROM AUTHOR]

In this paper, first, the effect of the interior permanent-magnet synchronous-motor (IPMSM) stator resistance to the maximum available motoring or regenerative braking torque is clarified. Then, a drive operating point is interpreted geometrically as the intersecting point of the torque-demand curve with either the maximum torque per ampere (MTPA) trajectory or the voltage-constraint curve inherently imposed by the motor and inverter under different control modes. Based on this principle, a novel voltage-constraint- tracking (VCT) field-weakening control scheme for IPMSM drives is proposed. The proposed method can automatically determine the desired MTPA or field-weakening control modes and provide a smooth transition between these two modes. No machine parameters are required in the field-weakening control mode, and no dc-link voltage sensor is used, rendering the proposed scheme rather robust. In addition, the minimum copper- loss operation can be preserved in the VCT-based control to achieve high efficiency. The proposed control method has a simple structure so that it can easily be implemented by modifying a conventional vector-controlled drive system for practical applications. Finally, a DSP-based prototype drive is constructed to verify the feasibility of the proposed scheme, and some experimental results are provided to demonstrate the satisfactory features. [ABSTRACT FROM AUTHOR]

• This paper exposes two special AC machines adaptable for electric vehicle application. • Their mathematical models are described and defined. • Their corresponding field oriented vector control topology was designed and verified through simulation steps. There has been a rapid adoption of electric vehicles (EVs), and the industry has been looking for the most enhanced traction system to improve performance and reliability. Such specifications are mostly dependent on the magnetic materials for brushless DC or AC machines, and typically EVs are manufactured with those machines. In the past two decades, there have also been improved performance ratings of power electronic devices. On one hand, making possible AC motors more suitable for EVs. On the other hand, it allows further advanced topology circuits to fit machines with two rotors or two stators. This paper shows two configurations of electrical machine control for EVs, discuss the pros and cons, and corresponding mathematical models have been developed in order to enhance a Field Oriented Control (FOC) strategy, which has been analyzed and studied through MATLAB based simulations, allowing novel design based on the analytical models developed by the authors. [Display omitted] [ABSTRACT FROM AUTHOR]

The thrust ripples in permanent magnet linear synchronous motor (PMLSM) are mainly generated by the distortion of the stator flux linkage distribution, reluctance force due to the relative position between the mover and stator, cogging force caused by the interaction between the permanent magnet (PM) and the iron core, and the end effects. This is the significant drawback which will deteriorate the performance of the drive system in high-precision applications. Comparing the complexity of the motor structure design to eliminate the thrust ripples, an optimal control method is more desirable. This paper focuses on thrust ripples reduction based on the predictive control algorithm. To minimize the thrust ripples and realize the high-precision control, the components of thrust ripples are extracted by finite element method (FEM) first and then compensated by injecting the instantaneous current to counteract the thrust ripples using the field-oriented control (FOC) method. The effectiveness of this proposed method is verified by the simulation using Simulink/Matlab according to the comparison between the compensation and noncompensation cases. [ABSTRACT FROM AUTHOR]