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Pole-changing permanent magnet (PCPM) motors have advantages over traditional permanent magnet synchronous motors (PMSM) in high-speed applications. However, changing the pole number of a motor requires reconstructing the stator winding. This increases both the cost and complexity. To solve this problem, a new type of single-winding PCPM motor with a pole-slot combination satisfying the rule of 2pa + 2pb = Z (the sum of the number of poles of the motor before and after the pole-changing is equal to the number of slots) is proposed in this paper. The multi-pole ratio pole-changing of the PCPM motor can be realized by combining the single-winding structure with another single-winding structure that satisfies the pa + pb = Z (the sum of the number of pole pairs of the motor before and after the pole-changing is equal to the number of slots) rule. Through this method, there is no need to reconstruct the stator winding when a pole is changed, Only by changing the phase sequence and direction of the armature current, the switching process is rapid, and the online pole-changing can be realized. This single-winding pole-changing method can flexibly realize the conversion of three pole number modes without increasing the additional winding cost and complexity. Finally, the rationality of the proposed pole-changing method is verified by finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

To improve the adaptability of sensorless control in the full-speed range of a dual three-phase permanent magnet synchronous motor (DTP-PMSM), an improved sensorless control strategy based on a variable-gain super twisting algorithm sliding mode observer (VGSTA-SMO) along with harmonic component compensation has been introduced in this paper. First, the super twisting algorithm sliding mode observer (STA-SMO) is introduced to reduce the inherent chattering phenomenon of traditional SMOs. Then, the variable gain of this STA-SMO is designed to improve the observation adaptability at different rotor speeds. Meanwhile, considering that the harmonic components, especially at low rotor speeds, in the stator current can affect the observation accuracy of this VGSTA-SMO, a least mean squares adaptive notch filter (LMS-ANF) is employed to implement online harmonic compensation. Finally, comparative experiments with different methods in the full-speed range are conducted and compared to verify the effectiveness of the proposed novel sensorless control strategy whose observation deviation is about 2% even when the rotor speed is as low as 100 rpm. [ABSTRACT FROM AUTHOR]

Motor current signature analysis (MCSA) offers a non-invasive approach to early detect different faults in squirrel-cage induction motors (SCIMs). Every fault normally adds some specific harmonics to the motor current and the MCSA typically proposes the fault diagnosis by detecting these harmonics. Using the rotor–stator mutual-inductance curve, this paper proposes an analytical approach to determine broad sets of harmonics that are presenting in the healthy SCIM current or are adding to the current by broken rotor bar (BRB) fault, mixed eccentricity (ME) fault and combined BRB-ME fault. The broad harmonic sets are attained due to applying exact form of the inverse of the air gap function, using exact form of the stator and rotor turn functions and taking every integer harmonic of the stator current into account. The extensive harmonic sets give higher degrees of freedom to attain the most appropriate harmonics to establish fault diagnosis techniques. Further study shows that many BRB-related harmonics are also present in the healthy state with lower amplitudes and that the ME fault magnifies some well-known BRB-related harmonics as well as the 3rd harmonic. In addition, the combined BRB-ME fault produces harmonics that are sidebands around the harmonics produced by the single ME or BRB fault. Simulation results based on the finite elements method and corresponding experimental test results confirm the analytically achieved results. [ABSTRACT FROM AUTHOR]

The flux observer method is widely utilized as a sensorless control technique in which the stator or rotor flux of IPMSM can be measured with a closed-loop observer or an integrator. However, DC-offset (DCoff), the ramp signal, and harmonics are consistently present in the acquired rotor flux because of an unidentified starting value, errors in the integral computation's current detection, and the inverter's nonlinearity. The aforementioned interference signals will drastically reduce the sensorless control efficacy. This work introduces an enhanced flux estimator with a negative feedback loop and PI controller to overcome the DC drift problem resulting from a pure integrator and a low-pass filter. Moreover, an optimal design approach of flux estimator structures with a broad range of speeds for Interior permanent magnet synchronous motor (IPMSM) drives is proposed, which utilizes an integrated topology of the voltage and current models incorporating a DC-offset PI-correction loop, actual and estimated flux magnitude's correction error. The flux vector's initial inaccuracy is eliminated, together with the DCoff and drift in the acquisition channel. A phase-locked-loop state estimator is utilized to derive the speed and position from the actual and estimated flux. The effectiveness and superiority of the suggested approach were proven by simulation and experimental findings for the IPMSM drives, which displayed high dynamic performances over varying scenarios. This reliable approach, including sensorless control, is suitable for all AC motors with sinusoidal flux distributions over a wide speed range. [ABSTRACT FROM AUTHOR]

In this work, a linear quadratic regulator controller is utilized to optimize the gains of the machine-side converter and grid-side converter controllers. The DC-link voltage and the rotational speed of the doubly-fed induction generator are optimally regulated by these controls. Additionally, the small-signal stability of the proposed system has been evaluated using the linearized model of the system. The small-signal stability analysis of the designed system has been accomplished through the application of the eigenvalues and participation factors technique. The suggested controller has been tested in a variety of operating conditions under small disturbances. MATLAB/SIMULINK simulation simulations have been used to evaluate the efficacy of the suggested optimal control system. Additionally, the generator-angular speed and DC-link voltage dynamic performances demonstrate the efficacy of the proposed controller. Finally, the robustness of the proposed controller has also been tested and validated using OPAL-RT technology under large perturbations at stator terminal voltage. [ABSTRACT FROM AUTHOR]

Direct torque control with space vector modulation has been increasingly attracting emphasis for permanent‐magnet synchronous machine control, benefiting from a high dynamic response and low torque ripple. However, the rapid tracking performance of torque and stator flux linkage is gradually deteriorating as the machine enters the overmodulation region because of the output‐voltage limitation of the inverter. Therefore, to enhance the system tracking performance in the overmodulation region, an innovative overmodulation method based on torque and flux optimal tracking is proposed. In contrast to the conventional overmodulation method where only one of the torque and stator flux linkage tracking is considered, the proposed strategy first constructs the weightless cost function to achieve a trade‐off control between the torque and stator flux linkage. Then, by using an equivalent geometric path to intuitively express the weightless cost function, the minimum cost function can be easily solved and the optimal output voltage vector can be determined correspondingly, to achieve the fast‐tracking of both the torque and stator flux linkage. Additionally, the voltage utilization of different overmodulation schemes is also analysed. Finally, the experimental results demonstrate the efficiency and practicality of the proposed strategy. [ABSTRACT FROM AUTHOR]

Towards complex coupled molecular motions, the remote handedness inversion of a helicene moiety was achieved by a rotary molecular motor. The use of a specifically engineered dynamic helicene stator in a novel overcrowded‐alkene second‐generation molecular motor based on a fluorinated dibenzofluorene fragment allows for an unprecedented control over helicity inversion. This is achieved by the mechanical coupling of the rotation of the rotor to the helicene inversion of the stator half via a remote chirality transmission process. Thus, the unidirectional rotary motion generated upon irradiation is used to invert the dynamic stereochemistry of a helicene, leading to a 6‐step cycle with eight intermediates. In this cycle, both alternation between P and M configurations of the helicene stator and dynamic thermal interconversion (paddling motion) can be achieved. In‐depth computational and spectroscopic studies were performed to support the associated mechanism. The control over coupled motion and dynamic helicity offers prospects for the development of complex responsive systems. [ABSTRACT FROM AUTHOR]

MotY homologs are present in a variety of monotrichous bacterial strains and are thought to form an additional structural T ring in flagellar motors. While MotY potentially plays an important role in motor torque generation, its impact on motor output dynamics remains poorly understood. In this study, we investigate the role of MotY in P. aeruginosa, elucidating its interactions with the two sets of stator units (MotAB and MotCD) using Förster resonance energy transfer (FRET) assays. Employing a newly developed bead assay, we characterize the dynamic behavior of flagellar motors in motY mutants, identifying MotY as the key functional protein to affect the clockwise bias of naturally unbiased motors in P. aeruginosa. Our findings reveal that MotY enhances stator assembly efficiency without affecting the overall assembly of the flagellar structure. Additionally, we demonstrate that MotY is essential for maintaining motor torque and regulating switching rates. Our study highlights the physiological significance of MotY in fine-tuning flagellar motor function in complex environments. [ABSTRACT FROM AUTHOR]

In the traditional predictive torque control strategy, the cost function considers two different control objectives: stator flux and torque. Therefore, it is necessary to reasonably set the weighting factor to ensure that the optimal voltage vector is accurately selected during the control process, thereby achieving better torque and flux control performance. In view of the complex tuning process caused by traditional predictive torque control setting method of weighting factor, a new weighting factor selection method for permanent magnet synchronous motor control system is proposed in this paper. The derivation process is based on the equivalent transformation between the torque–flux prediction and the voltage vector prediction. If both the cost functions of the torque–flux and voltage vector reach their minimum values, the same output voltage vector will be selected. Compared with previous studies, the algorithm proposed in this paper can find the precise location of the optimal weighting factor without changing the form of the cost function, which simplifies the parameter tuning process. Experimental results are also provided to validate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Winding inductance always plays a key role in the electromagnetic performances of stator surface-mounted permanent magnet (SSPM) machines, including their flux-weakening capability, prospective fault current, power factor, current ripple, etc. Generally speaking, winding inductance mainly comprises three components: an air-gap component, a slot-leakage component, and an end-leakage component. In this paper, firstly, the winding pole pairs of SSPM machines are investigated based on the magneto-motive force-permeance model, through which the winding configurations can also be determined. Then, according to the winding configurations, three analytical expressions for each inductance component are derived to evaluate the winding inductance per phase. In addition, finite element analysis (FEA) is employed to verify the effectiveness of the derived analytical expressions. Meanwhile, three prototyped SSPM machines are manufactured, and their winding inductances are measured to further verify the analytical expressions. The measured results agree with both the analytical and FEA results very well. [ABSTRACT FROM AUTHOR]

Summary: Compared with asynchronous voltage modulations, the synchronous space vector modulation (Syn‐SVPWM) can suppress current harmonics for high‐power induction motors (IM) by generating symmetrical voltage pulses. However, it is difficult to build a high‐performance current regulator based on Syn‐SVPWM because of the requirements of fixed voltage phases and the nonsymmetrical switching sequences in Syn‐SVPWM. Therefore, this manuscript proposes the equivalent realization of Syn‐SVPWM by the concept of stator flux trajectory tracking (SFTT). The new method controls the stator flux vector to move along evenly distributed flux samples in the complex plane. Then, the synchronization and symmetries of voltage pulses are maintained by organizing the switching sequence between adjacent flux samples. Meanwhile, the torque can be changed by online updating the control period based on the inverse torque model. Consequently, the proposed method can provide fast torque response with Syn‐SVPWM in a simple manner because it does not have to compensate the phase contradiction and to extract the fundamental of sampled current. Both simulations and experiments have verified the effectiveness of proposed method. [ABSTRACT FROM AUTHOR]

In the variable frequency motor drive system, because the cable impedance does not match the motor impedance, the reflection wave of the voltage wave will be generated. The superposition of reflected voltage waves can lead to overvoltage at the motor ends, which can damage the insulation structure. In this paper, the equivalent circuit models of cable and stator winding are established, respectively. The overvoltage distribution under different power supply frequencies and cable lengths is simulated and analyzed. The influence mechanism of power supply frequency and cable length on the overvoltage distribution of stator winding are studied. The simulation results show that the overvoltage of the first pulse falling edge will be superimposed on the overvoltage of the second pulse rising edge under high-frequency conditions, resulting in a further increase in the overvoltage. The voltage appears in all coils after the middle of the winding. The ground voltage is up to 1.32 times the input voltage, and the inter-turn voltage is up to 9.2 times the average voltage. The increase in cable length will lead to an increase in ground voltage, but the increase in speed will slow down after exceeding the critical length of 300 m. The maximum ground voltage can reach 1.93 times of the input voltage, which is 3.6% different from the calculation result under ideal conditions. The inter-turn voltage changes with the cable length in an N-shaped manner, up to 185 V. The results of this paper are of great significance to further study the insulation design of generator end input. [ABSTRACT FROM AUTHOR]

To maximize the performance of rotating machines, it is essential to establish a design method with minimal arbitrariness. This paper proposes a self‐assembling method to design stator slots for alternating current (AC) rotating machines. First, we develop a line‐current approximation model of the stator winding using pulse‐width modulation technique and realize an ideal spatial magnetic flux density distribution. Subsequently, we design the realistic stator with an acceptable current density of the winding by forming unique slot shapes in a self‐assembling manner under two synthetic conditions using the developed line‐current approximation model as the starting model. The designed stator realizes a rotating magnetic field similar to the conventional design results. Additionally, we perform an analysis of motor rotation characteristics by combining the self‐assembled stator with a surface‐mounted permanent magnet rotor to determine the possibility of a higher output compared to that when using a conventional stator. The self‐assembled motor without relying on empirical rules shows a possibility of further improving the torque characteristics, thereby contributing to designing the AC rotating machines. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this paper, a state and parameter observer, based on a novel extended Kalman filter (EKF), is designed to solve the parameter variations dependent estimation performance deterioration of induction motor (IM) drive systems. The proposed EKF based observer algorithm performs online estimation of the rotor mechanical speed, stator stationary axis component of the stator currents and rotor fluxes, stator resistance, rotor resistance, reciprocal of the total inertia of the system, and load torque including viscous friction term in a single EKF by using measured rotor mechanical speed and stator currents. Thus, frequency and temperature-dependent variations of the resistances are estimated to be updated in the observer, which leads to control performance enhancement of the IM drive. Moreover, to rise the dynamic performance of the observer, the load torque and reciprocal of the total inertia of the system which are mechanical parameters are also estimated. To verify the robustness of the IM drive and the estimation performance of the proposed observer, they have been tested under challenging scenarios including changes in parameters and speed reference. Moreover, the estimation performance of the proposed ninth order observer is compared with that of a sixth order EKF estimating the same electrical parameters by using directly measured speed. Ultimately, the simulation results obviously reveal the efficacy of the proposed IM drive. [ABSTRACT FROM AUTHOR]

A novel method is presented for determining the derating factors of a three‐phase induction motor under the condition of the unbalanced supply voltages. In this method, a mechanical system is used which consist of the a centrifugal pump, two valves, a DC motor, which are connected to the shaft of the three‐phase induction motor. A sliding mode control system is used for position control of the DC motor for adjusting the valve angle for derating the induction motor. The authors present the results of an experiment in which a three‐phase induction motor was subjected to various unbalanced voltage conditions. The results of simulations were used to look into what happened when there were different levels of imbalanced voltage. This was done to determine how these situations changed an induction motor's speed, torque, and efficiency. For this system, the stator current would be greater than the rated current if there was an imbalance in the supply voltage. Therefore, to reduce the amount of power that the three‐phase induction motor can produce, the control system uses a DC motor to reduce the angle of one of the two valves. This decreasing angle continues until the root mean square value of the stator current returns to the rated current. At this point, the derating factor may be calculated by dividing the output power of the three‐phase induction motor in the unbalanced condition by the output power when there are ideal sinusoidal. The MATLAB SIMULINK environment is utilised to perform simulations of the proposed system. [ABSTRACT FROM AUTHOR]

The open‐circuit magnetic field of the V‐shaped interior PM (IPM) machine is predicted by the analytical method. The method is implemented following the basic principle of the subdomain method. The machine model is divided into five different regions, including rotor slot, magnetic barrier, air gap, stator slot, and stator slot opening. To perform the analytical prediction process in the polar coordinate system, these regions should be transformed into the appropriate subdomains. The last four regions can be transformed into the subdomains with the required shape based on the existing method. The rotor slot cannot be treated as a single subdomain, for the shape of which is irregular. Herein, the PM and vacuum region in the rotor slot is divided into several fan‐shaped subdomains. The division method is described clearly. Then, the boundary conditions alongside the interface between adjacent subdomains are derived based on function transformation. On this basis, the open‐circuit magnetic field of the IPM machine can be predicted. The magnetic field of the 6p/36 s V‐shaped IPM machine is obtained by the proposed method, finite element method simulation, and experiment, respectively. Additionally, the comparison results verify the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In the context of eccentric micro-scale Taylor–Couette flow, variations in localized flow scales result in a non-uniform fluid–solid interface slip state, distinct from the typically studied uniform slip velocity distribution. This study introduces a boundary condition definition method aimed at characterizing partial slip states, complemented by a coupled iterative analysis system tailored to address this complexity. Key contributions include the development of a method for calculating the limiting shear stress, which considers local velocity gradients and pressures. Validation demonstrates that the locally derived slip state aligns more closely with Knudsen number distributions of local flow scales compared to traditional uniform slip models, and exhibits greater consistency with experimentally measured pressure distributions. Additionally, the study reveals that eccentric Taylor–Couette flow, characterized by significant variations in local flow scales and strong self-induced pressure effects, leads to complex distributions of local pressure, velocity gradients, and differences in local slip velocities. Specifically, the non-uniform distribution of local pressure gradients due to eccentricity results in partial slip occurring predominantly on the rotor in regions with positive pressure gradients, and on the stator in regions with negative pressure gradients. Furthermore, the variation in gap height exerts a greater influence on local slip compared to rotational speed and eccentricity ratio. Under certain conditions influenced by pressure gradients, the slip velocity on the rotor may exceed its tangential speed. [ABSTRACT FROM AUTHOR]

The inlet and outlet radii are important design parameters that directly determine the internal/external characteristics and cavitation characteristics of the torque converter (TC). The stator and turbine are the main areas of cavitation in TCs. Based on this, the outlet radius of the stator and turbine is taken as the research object of this paper. In this study, computational fluid dynamics (CFD) models of different turbine and stator outlet radii are established, and the influence of stator/turbine outlet radius design parameters on the performance of TCs is revealed by comparing the internal/external characteristics and cavitation characteristics. The results show that reducing the outlet radius of the stator/increasing the outlet radius of the turbine will cause the stator and the turbine blade to be shorter, increase the area of the vaneless region between the impellers, and reduce the risk of cavitation in TCs. However, it will also lead to a decrease in the external characteristics of the low-speed ratio (SR) condition and an increase in the external characteristics of the high-SR condition. With the decrease in the stator outlet radius/the increase in the turbine outlet radius, the mass flow rate of TCs will decrease, and the mass flow loss caused by cavitation will decrease from the original 42.51 to 6.95 and 21.95 kg/s, respectively. The suppression rates of the stator/turbine outlet radius on TC cavitation volume are 58.894% and 52.359%, respectively. The research results of this study can provide practical engineering guidance for the design of high-performance TCs and cavitation suppression. [ABSTRACT FROM AUTHOR]

In vector-controlled Permanent Magnet Synchronous Motors (PMSMs), measuring the motor flux angle, particularly the rotor position, is essential. If a pulse error occurs during motor control using an encoder, it becomes impossible to accurately estimate the rotor position, leading to incorrect position angle information being used in the coordinate transformation. This mismatch causes discrepancies between the commanded three-phase stator current and the actual current applied to the motor. As a result, the motor and inverter output and efficiency decrease, and the control performance deteriorates. Therefore, research is necessary to compensate for such errors. This paper proposes an algorithm that detects pulse errors occurring in incremental encoders and automatically switches to the Hall sensor control mode to compensate for the encoder pulse errors. The proposed algorithm, based on Hall sensors, has the advantage of not significantly affecting control delays, which could be problematic in high-speed operating ranges; thus, effective control is maintained even in such situations. [ABSTRACT FROM AUTHOR]

FliL is a bacterial flagellar protein demonstrated to associate with, and regulate ion flow through, the stator complex in a diverse array of bacterial species. FliL is also implicated in additional functions such as stabilizing the flagellar rod, modulating rotor bias, sensing the surface, and regulating gene expression. How can one protein do so many things? Its location is paramount to understanding its numerous functions. This review will look at the evidence, attempt to resolve some conflicting findings, and offer new thoughts on FliL. [ABSTRACT FROM AUTHOR]

This paper proposes a method for the torque ripple reduction of an open-end winding interior permanent magnet synchronous motor (OEW-IPMSM) using direct self-control (DSC). The conventional DSC has been researched in high-power systems because of its advantages in terms of a low switching frequency and a fast response of torque. Nevertheless, high torque ripple is a disadvantage of the conventional DSC. This is because the trajectory of the stator flux is controlled in the shape of a hexagon for lower switching frequencies and by applying hysteresis torque control. In this paper, predictive torque control using a mathematical model of an OEW-IPMSM is presented to improve the quality of the torque control. In addition, the presented method addresses the trajectory control of the flux using the diverse voltage vectors of the dual inverter. The validity of the presented method is demonstrated by simulations and experimental results. [ABSTRACT FROM AUTHOR]

Tandem bladed axial flow compressor concept has immense potential for increasing the stage loading over conventional stages. This infers significant improvement in gas turbine engine operational economics and performance. However, implementation of tandem configuration invites additional three dimensionalities in the flow field. This complicates the design process limiting the realization of the tandem bladed rotor concept. The present study addresses the strategies for development of a low-speed axial compressor design implementing tandem bladed rotor and single stator. Both the rotor and stator flow mechanisms have been investigated in detail using steady state simulations. A highly loaded tandem bladed rotor is followed by single bladed stator which handles the highly swirled flow. The single blade configuration of stator results in higher diffusion factor which is more susceptible to the flow separation. Moreover, a dual wake structure evolves through the rotor passage due to highly loaded individual blades. The stage design follows an unconventional approach of tandem rotor-single stator over the reported tandem rotor-tandem stator or only tandem bladed stator configuration. The aerodynamic match between the tandem bladed rotor and stator has been of critical importance in development of this design. The rotor has been designed for highest possible energization of flow by fine tuning the variation of tandem nozzle geometry throughout the span to complement the intended loading profile. The stator is aimed at letting the flow pass through with a chordwise varying diffusion profile. The novelty of the work lies in discussion of tandem rotor and single bladed stator flow physics altogether highlighting the interdependence of decision-making process for both. [ABSTRACT FROM AUTHOR]

This paper addresses performance degradation in nonlinear flux linkage algorithms, arising from estimation errors in rotor flux linkage due to fluctuations in current and temperature. We introduce a parameter-adaptive flux linkage model using MRAS, which dynamically adjusts the rotor flux linkage, significantly minimizing estimation errors and improving control performance. When the rotor flux linkage of the motor undergoes sudden changes, the nonlinear flux linkage model shows a speed fluctuation of 5%, whereas the parameter-adaptive flux linkage model reduces the error to 0.6%. The algorithm demonstrates strong robustness when the stator resistance undergoes a sudden change. The control effectiveness under conditions such as load start and load mutation is excellent. Simulations and experiments demonstrate that the parameter-adaptive flux linkage model improves the estimation accuracy of the rotor position when motor parameters change. [ABSTRACT FROM AUTHOR]

The flux switching permanent magnet (FSPM) motor is a stator permanent magnet motor. The typical FSPM motor is doubly salient, which generates torque ripple and affects the rotation smoothness. In this paper, the influence of salient pole geometric sizes on motor torque performance is studied to reduce motor torque ripple and improve motor torque density. First, three indicators are defined to present the motor torque characters, including the average torque, torque ripple, and the volume of permanent magnet material usage. Then, the model of salient pole geometric sizes function to the three indicators is created. With this model, the optimal solution is obtained by the multi-objective numerical optimization. Based on the optimized results, the rotor shape is refined and analyzed as the supplementary to reduce the torque ripple further. Finally, the results show that the optimization procedure in this paper can effectively weaken the torque ripple, reduce the permanent magnet material usage, and improve the average output torque of the motor. Based on the optimized data, the prototype machine is built to verify the analysis results and prove the feasibility of this research. [ABSTRACT FROM AUTHOR]

A Rotary-Pulsation Apparatus (RPA), also known in the literature as a Rotational Hydrodynamic Cavitation Reactor (RHCR), is a device which typically consists of a rotating mechanism that generates pulsations or vibrations within a fluid. This can be achieved through various means such as mechanical agitation, pneumatic pulses, or hydraulic forces. It is widely used in food, chemical, pharmaceutical, and microbiological industries to improve the mixing of different fluids, dispersion, pasteurization, and sterilization. In the present paper, a CFD study was conducted to develop and optimize the geometry of the RPA's rotor and stator to induce cavitation in the fluid flow. The effect of cavitation has the potential to improve dispersion and emulsion properties and to significantly reduce operation pressure, in comparison to conventional mixing systems. [ABSTRACT FROM AUTHOR]

One of the major challenges of today’s rotating machine manufacturing industries is finding effective techniques to prevent early mechanical or electrical failure. Efficient troubleshooting methods must be developed for rotating electrical machines, such as three-phase and multiphase electrical induction or synchronous machines. A novel method for fault detection in a Wound Rotor Induction Machine (WRIM) is presented in this paper. Its originality lies in the determination of current rise and fall times in healthy and InterTurn short-Circuit Fault (ITSCF) cases. The method is based on using the two-current (isd, isq) sigmoid transform (ST) of Park’s vector approach. A WRIM with a nominal power of 0.3 kW is used for the analytical and experimental studies. The type of fault detection being studied is short circuit InterTurns on one phase of the stator winding. The results are promising because the methodology used is simple, fast, and accurate for diagnosing this type of fault, and can detect a low number of short-circuit InterTurns in the stator winding. [ABSTRACT FROM AUTHOR]

This study presents a comparative analysis of Direct Torque Control with Space Vector Modulation (DTC-SVM) and Finite Control Set Model Predictive Control (FCS-MPC) applied to five-phase induction motors. Five-phase induction motors offer enhanced performance, reliability, and efficiency over traditional three-phase motors, making them suitable for high-reliability applications. The performance of DTC-SVM and FCS-MPC is evaluated through experimental implementation on a 3.5 kW five-phase induction motor, focusing on both dynamic response during speed reference changes and load variations, and static response, under steady-state conditions, as well as energy quality, specifically stator voltage and current. Experimental results show that FCS-MPC provides superior dynamic response, effectively managing speed changes and load variations, while DTC-SVM, owing to its fixed switching frequency, excels at reducing torque ripple and minimizing stator current harmonics. The choice between DTC-SVM and FCS-MPC depends on the application's needs, weighing dynamic performance, torque stability, and harmonic content. This study provides valuable insights for optimizing five-phase induction motor control and encourages future research to refine these methods or develop hybrid approaches that combine their strengths. [ABSTRACT FROM AUTHOR]

Stator faults are one of the common issues in pumped storage generators, significantly impacting their performance and safety. To ensure the safe and stable operation of pumped storage generators, a stator fault diagnosis method based on an improved short-time Fourier transform (STFT)-support vector data description (SVDD) hybrid algorithm is proposed. This method establishes a fault model for inter-turn short circuits in the stator windings of pumped storage generators and analyzes the electrical and magnetic states associated with such faults. Based on the three-phase current signals observed during an inter-turn short circuit fault in the stator windings, the three-phase currents are first converted into two-phase currents using the principle of equal magnetic potential. Then, the STFT is applied to transform the time-domain signals of the stator's two-phase currents into frequency-domain signals, and the resulting fault current spectrum is input into the improved SVDD network for processing. This ultimately outputs the diagnosis result for inter-turn short circuit faults in the stator windings of the pumped storage generator. Experimental results demonstrate that this method can effectively distinguish between normal and faulty states in pumped storage generators, enabling the diagnosis of inter-turn short circuit faults in stator windings with low cross-entropy loss. Through analysis, under small data sample conditions, the accuracy of the proposed method in this paper can be improved by up to 7.2%. In the presence of strong noise interference, the fault diagnosis accuracy of the proposed method remains above 90%, and compared to conventional methods, the fault diagnosis accuracy can be improved by up to 6.9%. This demonstrates that the proposed method possesses excellent noise robustness and small sample learning ability, making it effective in complex, dynamic, and noisy environments. [ABSTRACT FROM AUTHOR]

Flux reversal machine (FRM) belongs to the stator permanent magnet (PM) machine, which has the advantages of high reliability, high efficiency, and simple structure. However, large torque ripple and low torque density limit the development prospect of FRMs. Therefore, a wavy rotor FRM (WR-FRM) with curved stator slots is proposed, which can reduce the torque ripple while improving the average torque. The top surface of the rotor tooth consists of three sinusoidal functions, and the stator slots are constructed with a spline curve. To obtain better electromagnetic performance, the multi-objective genetic algorithm is used to optimize the FRM and the WR-FRM. Finally, the electromagnetic performances of the two machines is analyzed and compared by the finite element method. The results show that compared with the FRM, the torque generated by the unit volume of PM is increased by 36.47%, and the torque ripple is reduced by 62.7%. [ABSTRACT FROM AUTHOR]

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Inverter-fed machines are widely used in electric vehicle drive systems and have shown a trend toward high voltage and frequency in recent years. They are subjected to multiple types of stress during operation, causing potential short-circuit fault damage to the stator winding insulation. Online condition monitoring of the insulation before or in the early stage of the short circuit fault can effectively reduce maintenance costs and ensure its health. This paper reviews and summarizes the deterioration mechanism and the recent online electrical monitoring techniques. First, four types of failure stress and each type's failure factors and mechanisms are analyzed. The coupling effect and overall process of multi-physical fields on stator insulation failure are considered. Secondly, the latest online electrical monitoring technologies are summarized. Each technique's principles, methods, advantages, and disadvantages are analyzed. Finally, existing problems and possible directions for improvement in current research are discussed, focusing on their feasibility and accuracy in practical applications. [ABSTRACT FROM AUTHOR]

The low specific speed centrifugal pump plays a crucial role in industrial applications, and ensuring its efficient and stable operation is extremely important for the safety of the whole system. The pump must operate with an extremely high head, an extremely low flow rate, and a very fast speed. The internal flow structure is complex and there is a strong interaction between dynamic and static components; consequently, the hydraulic excitation force produced becomes a significant factor that triggers abnormal vibrations in the pump. Therefore, this study focuses on a low specific speed centrifugal pump and uses a single-stage model pump to conduct PIV and pressure pulsation tests. The findings reveal that the PIV tests successfully captured the typical jet-wake structure at the outlet of the impeller, as well as the flow separation structure at the leading edge of the guide vanes and the suction surface. On the left side of the discharge pipe, large-scale flow separation and reverse flow happen as a result of the flow-through effect, producing a strong vortex zone. The flow field on the left side of the pressure chamber is relatively uniform, and the low-speed region on the suction surface of the guide vanes is reduced due to the reverse flow. The results of the pressure pulsation test showed that the energy of pressure pulsation in the flow passage of the guide vane occurs at the fBPF and its harmonics, and the interaction between the rotor and stator is significant. Under the same operating condition, the RMS value distribution and amplitude at fBPF of each measurement point are asymmetric in the circumferential direction. The amplitude of fBPF near the discharge pipe is lower, while the RMS value is higher. A complex flow structure is shown by the larger amplitude and RMS value of the fBPF on the left side of the pressure chamber. With the flow rate increasing, the energy at fBPF of each measurement point increases first and then decreases, while the RMS value decreases, indicating a more uniform flow field inside the pump. [ABSTRACT FROM AUTHOR]

In order to optimize the electromagnetic performance of a permanent magnet synchronous motor (PMSM) during operation, this paper takes the size of the stator slot structure of the motor as the optimization variable and the peak cogging torque and no-load back electromotive force (EMF) amplitude of the motor as the optimization objectives. A multi-objective optimization method based on the particle swarm optimization (PSO) algorithm is adopted to obtain a structural parameter combination that minimizes the peak cogging torque and no-load back EMF amplitude while meeting the reasonable range requirements of magnetic flux density amplitude. The optimized motor structure design prototype is experimentally verified. The results show that through multi-objective optimization based on the PSO algorithm, the electromagnetic performance of the motor has been improved, with a reduction of 36.33% in peak cogging torque and 2.65% in peak no-load back EMF, indicating a reasonable magnetic flux density amplitude. The experimental results of the optimized prototype show that the difference between the theoretical simulation values and the experimental values is within a reasonable range, which verifies the effectiveness of the multi-objective optimization method. [ABSTRACT FROM AUTHOR]

Three-phase induction motors play a key role in industrial operations. However, their failure can result in serious operational problems. This study focuses on the early identification of faults through the accurate diagnosis and classification of faults in three-phase induction motors using artificial intelligence techniques by analyzing current, temperature, and vibration signals. Experiments were conducted on a test bench, simulating real operating conditions, including stator phase unbalance, bearing damage, and shaft unbalance. To classify the faults, an Auto-Regressive Neural Network with Exogenous Inputs (NARX) was developed. The parameters of this network were determined through a process of selecting the best network by using the scanning method with multiple training and validation iterations with the introduction of new data. The results of these tests showed that the network exhibited excellent generalization across all evaluated situations, achieving the following accuracy rates: motor without fault = 94.2 %, unbalanced fault = 95%, bearings with fault = 98%, and stator with fault = 95%. [ABSTRACT FROM AUTHOR]

An inertial linear ultrasonic motor with a novel double-stator structure is proposed for achieving higher performance and resolution in this paper. Utilizing a symmetrical structure and single sawtooth wave signal, the prototype is capable of outputting effective linear motion based on inertial movement. The validity and rationality of the prototype are investigated by conducting finite element analyses. The experimental setups are built up to acquire the output characteristics of the motor. The experimental results indicate that the motor can achieve a maximum output velocity of 8.746 mm/s and thrust force of 1.645 N, which is almost twice the output performance of a motor with a single stator. The displacement solution of the motor can be adjusted by changing the amplitude of the voltage, with a resolution of 27 nm. Simultaneously, the relationships between the output characteristics and the input parameters are measured and analyzed during the experiments. Compared to the actuators with complex structures and multi-signal drives, the proposed motor exhibits the merits of higher output performance with the double-stator structure, providing an alternative direction for the further development of the inertial linear ultrasonic motor. [ABSTRACT FROM AUTHOR]

This study analyzes the turbomachinery flow of a gas turbine using OpenFOAM, an open-source CFD code. While foam-extend, a version of OpenFOAM, includes tools for turbomachinery analysis, some of its codes are incomplete, resulting in incorrect results. Consequently, this study required the investigation and correction of the solvers and libraries. Specifically, foam-extend-4.1 and a compressible multi-reference-frame solver were utilized. Two primary errors related to temperature calculation were identified. The first error involved temperature discontinuity at the interface between the stator and rotor domain when using the mixingPlane. The second error was related to temperature rising at the wall. To address the temperature discontinuity problem, the rothalpy jump equation in the enthalpyJump code was modified from a scalar product to an inner product of vectors. To resolve the high-temperature problem at the wall, modifications were made to the energy equation code in iEqn.H. A rothalpy separation was introduced, and the rothalpy equation was adjusted to mimic the enthalpy equation. The results obtained with the corrected codes were consistent with those from the commercial code, demonstrating the effectiveness of the modifications. [ABSTRACT FROM AUTHOR]

Compared with a traditional low‐speed high‐torque permanent magnet synchronous motor (PMSM), a permanent magnet (PM)/reluctance hybrid rotor dual‐stator synchronous motor (PM/RHRDSSM) has the advantages of high torque density and high space utilization. This type of motor is composed of a "back‐to‐back" PM + reluctance hybrid rotor and an inner and outer double stator. The number of poles of the inner and outer unit motors is the same, and the inner and outer stator windings are connected in series, driven by a single inverter. Due to the special mechanical structure and electromagnetic relationship of PM/RHRDSSM, traditional PMSM and synchronous reluctance motor maximum torque per ampere (MTPA) control strategies are no longer applicable. In response to this issue, the authors establishe a PM/RHRDSSM mathematical model of stator winding series structure and propose a MTPA control strategy suitable for this new type of motor. This strategy is aimed at the special mathematical model of PM/RHRDSSM and derives the analytical expression of MTPA trajectory, which minimises the required stator current amplitude of PM/RHRDSSM at various load torques, thereby minimising the motor copper loss. Finally, the effectiveness and practicality of the proposed control strategy were verified through simulation and experiments. [ABSTRACT FROM AUTHOR]

In recent years, the use of permanent magnet synchronous motors has become popular. These engines are cheaper, lighter, and more durable. However, to control these motors, accurate information about the position of the rotor is necessary. For this reason, various methods have been used to improve the motor position estimation performance. One of these methods is estimation by injecting harmonic current into the stator winding. In this paper, using high-frequency currents injected into the stator, the rotor position in IPMSM motors is estimated. However, the response obtained has a DC offset due to the inaccuracy of the current measurement sensors, which causes an error in the estimation of the rotor position. The improved ePLL method was used to solve this problem. This method causes the convergence of the estimated position of the rotor to its real position by removing the noises of the current measurement circuit and the DC offset effect. The efficiency of this method has been proven first by simulation in MATLAB software, then in a Psim environment, and then implemented on the drive of a permanent magnet motor using a TMS320F28034 processor. [ABSTRACT FROM AUTHOR]

Vector-controlled drives require stator current information for use in current feedback and/or state variable estimators. That is why the detection and compensation of possible current sensor (CS) damage is so important. This article focuses on CS fault-tolerant control (FTC) in induction motor (IM) drive systems. In contrast to solutions known from the literature, two modified Luenberger observers (MLO) were applied, allowing for high-quality estimation of currents used in the detector and fault compensator. In a simple implementation of a detection algorithm based on residuals, an adaptive threshold coefficient was employed, enabling effective detection of various types of faults, regardless of whether the second CS was faulty or intact. The presented solution was evaluated during both motor and regenerative operation, with faults occurring in transient states, unlike solutions known in the literature. [ABSTRACT FROM AUTHOR]

Medium‐speed wind generators in the MW‐range with high‐temperature superconducting excitation winding are analyzed by means of non‐linear 2D and 3D FEM models. Besides an inverter‐based sinusoidal stator current feeding, a grid connection via a diode rectifier is analyzed by using coupled FEM and circuit simulations. The newly proposed modeling techniques are used to determine the excitation requirement for speed‐variable, unity power factor operation at constant stator voltage, as required for a diode rectifier feeding of the stator winding. 2D FEM models in the H‐A‐formulation are developed and used for the calculation of the hysteresis loss in the superconducting field winding at stationary operation as well as for an investigation of field current variations in the HTS field winding. The major modeling challenges consist in very long settling times of voltage‐fed models, several strong model non‐linearities and high requirements on the spatial discretization. Approaches for overcoming these difficulties with reasonable computational efficiency are proposed. [ABSTRACT FROM AUTHOR]

The uncontrollable angles (UAs) in direct torque control (DTC) algorithm is an important issue through which the effects of voltage vectors (VEs) on the magnetic flux and the torque are accurately determined. In this paper, a unique analysis of UAs is performed at different operating conditions, including parameters variations in two different strategies: Direct torque and stator flux control (DTC_SC) and (DTC_RC). Values of Those angles were accurately determined for wide speed, stator and rotor variations, and load changes. In addition, a detailed numerical comparison was performed in terms of these angles in the two strategies mentioned above for each operating condition. The comprehensive comparison showed the superiority of the DTC_RC strategy over its DTC_SC counterpart, being the maximum values of UAs in DTC_RC were 8°, 33°, and 21° versus 15°, 45°, and 38° in DTC_RC strategy for the following operations: Variable speed with variable stator resistance, variable speed with variable stator and rotor resistances, variable speed with variable load, respectively. MATLAB/Simulink results of the contributed analysis and comparisons were accomplished and validated. In addition, DS1103‐based experimental tests supported and verified the theoretical analysis. [ABSTRACT FROM AUTHOR]

Numerical simulations of a shrouded stator cascade with an inter-stage cavity were conducted using validated numerical methods to investigate the impact of different labyrinth seal structures and positions on the aerodynamic performance of the stator cascade. The study discussed the development trends of secondary flow motion and corner separation within the cascade under different labyrinth seal structures, evaluated the stator performance using total pressure loss coefficient and entropy-based loss coefficient, and revealed the interaction between cavity leakage flow and mainstream flow. The results indicate that individually changing the labyrinth seal structure or position has a negligible impact on stator performance, but simultaneously altering both the structure and position of the labyrinth seal can effectively reduce stator losses. The structure case 1-position case 2 labyrinth seal structure can reduce total pressure loss by 6.25%, while structure case 4-position case 4 reduces entropy increase loss coefficient by 7.67%. Additionally, it was found that changing the labyrinth seal structure and position can increase the circumferential velocity and momentum of cavity leakage flow at the cavity outlet, enhance the resistance of cavity leakage flow to circumferential secondary flow within the stator passage, and reduce stator losses. Altering the structure and position of the labyrinth seal effectively reduces the cavity leakage vortex at the leading edge of the cascade during the mixing process of cavity leakage flow with the mainstream, causing the passage vortex to move rearward axially. [ABSTRACT FROM AUTHOR]

The steady and unsteady flow properties of the National Aeronautics and Space Administration (NASA) single-stage transonic compressor stage 35 are numerically investigated through the Reynolds-averaged Navier–Stokes (RANS) simulation method. The main purpose of the present paper is twofold. One is to validate the capability of the Spalart–Allmaras (S–A)-Helicity-γ model in unsteady RANS (URANS) simulation for rotor–stator interaction of a whole-stage compressor, and another is to figure out the roles played by helicity modification and transition augmentation in improving the performance of traditional S–A model. The results of steady RANS simulation indicate that the S–A model with helicity regulation is more sensitive to vortex structures in the end wall and blade-tip regions, while the inclusion of transitional intermittency factor can help predict the important transition phenomenon in the midspan region. As the back pressure increases, the inaccuracy of flow fields exchange caused by the mixing plane method becomes nonnegligible for the prediction of aerodynamic performance and thermodynamic quantities. Thus, URANS simulation seems to be necessary for more accurate prediction of the flow details of the stator subjected to periodic sweep of the rotor wake. On the suction surface of the stator, a turbulent separation bubble near the leading edge is transported downstream and merges into another separation bubble with much lower turbulence intensity at the trailing edge periodically. The combination of helicity and transition modifications provides advantages over traditional S–A model in describing this process, quite similar to its performance in steady simulations. [ABSTRACT FROM AUTHOR]

To comprehensively explore flow control method of profiled end wall for turbine stage at low Reynolds numbers, a surrogate model optimization platform including non-uniform rational B-spline surface parameterization method, support vector regression, and improved chaos particle swarm optimization algorithm is integrated. Optimization designs have been carried out for stator profiled end walls, rotor profiled end wall, and combined end walls, respectively. The results indicate that under the constraint of the output power, the application of various profiled end wall design cases all can effectively improve the aerodynamic performance of the turbine stage. By organizing the flow field of downstream rotor, the profiled end wall of stator can significantly affect the stage efficiency. The flow control benefits of the profiled end wall of the rotor is from the obstruction of the cross migration of the pressure side leg of the horseshoe vortex. The application of profiled end wall on stator has the most practical engineering value. Self-organizing maps and Shapley methods are used to explore potential correlation information of aerodynamic parameters and summarize design experience. The sensitive design variables of profiled end walls are extracted. Based on the local controllability of NURBS surfaces, the regions that affect the stage efficiency are mainly concentrated in the middle of the stator passage, near the stator trailing edge and near the rotor leading edge. The regions with a significant impact on the output power of the turbine stage are near the trailing edge of the rotor and stator. The corresponding design rules of end walls modeling are summarized. [ABSTRACT FROM AUTHOR]

The axial gap structure of a half‐wave rectified variable field flux motor (AG‐HVFM) has been proposed, which has a double stator structure and field winding short‐circuited by a diode. Although the AG‐HVFM can achieve a high‐efficiency drive in wide speed and torque range via variable field flux control, its structure deteriorates the average torque and torque ripple. In this paper, we sequentially design the core shape, aspect ratio, and current control method for an AG‐HVFM to improve its torque characteristics. [ABSTRACT FROM AUTHOR]

To further improve the operating efficiency of linear induction motor, this paper proposes a loss minimization model predictive current control method based on governable loss online calculation. First, the method derives the equivalent circuit of linear induction motor containing independent iron loss branches, and establishes the loss model containing iron loss. Second, the expressions of stator d‐axis current with governable losses and secondary flux amplitude are derived from theoretical analysis, and then a given value of stator d‐axis current is derived when the governable losses are minimal. Then, a chain observer is designed to observe the secondary flux and calculate the governable loss and stator d‐axis current under the current operation. Finally, a method is proposed to introduce the stator d‐axis current observation results into the model predictive current control, which ensures the loss suppression effect and improves the dynamic performance at the same time. In addition, this article also compares the loss minimization controllers with or without iron loss. The simulation results are consistent with the theory, and the optimal control of the secondary flux of the linear induction motor can be successfully realized, thus effectively reducing the energy loss of the motor in the dynamic operation process. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Rotor bar breakage in induction motors is often detected by analysing the signatures in the stator current. However, due to the alteration of the current spectrum, traditional methods may fail when inverter-fed motors operate with closed-loop control using a cascade structure to regulate the speed. In this paper, the potential of zero-sequence voltage analysis to detect this fault is investigated, and a new index to quantify the severity of the fault based on this signal is proposed. Signals from motors operating under different control strategies and signals from motors powered from the mains are considered to verify the robustness of the proposed fault severity index. As a result, in all the analysed conditions the value of the proposed index for the healthy motor is found to be approximately 0.010, while for the faulty machine it is between 0.110 and 0.252. [ABSTRACT FROM AUTHOR]