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A hybrid ferrite‐Al‐Ni‐Co permanent magnet assisted synchronous reluctance motor (PMa‐SyRM) for an air‐conditioner compressor is proposed. Al‐Ni‐Co PMs have high residual flux density similar to rare‐earth PMs such as Nd‐Fe‐B and Sm‐Co. Therefore, the performance parameters of the PMa‐SyRM such as power factor, efficiency etc., with Al‐Ni‐Co PMs can be improved without significantly increasing the cost of the motor. However, Al‐Ni‐Co PMs have a steep IInd‐quadrant B‐H curve, and the challenge lies in addressing their demagnetisation issues. In the proposed hybrid PMa‐SyRM, the rotor geometry is suitably optimised for placing the Al‐Ni‐Co PMs in the centre flux barriers to address the demagnetisation issues. Further, an analytical magnetic circuit is presented to design the proposed PMa‐SyRM. Later, 2‐D finite element analysis of the proposed motor including the demagnetisation analysis of PMs and stress analysis of the rotor is carried out and presented. A prototype is fabricated, experimental validation is carried out, and the results of the performance and cost are compared with that of ferrite and hybrid ferrite‐Nd‐Fe‐B PMa‐SyRM. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis, electromagnetic evaluation, and prototyping of a novel motor structure called the sinusoidal rotor switched reluctance motor. In this innovative design, a significant departure from the conventional switched reluctance motor is observed, as modifications are made to the rotor with the goal of reduction torque ripple and radial force characteristics. Importantly, despite these advancements, the proposed motor retains the weight and volume characteristics of the traditional, type. The key attributes of these motors have been thoroughly assessed using the three‐dimensional finite element method, complemented by a sensitivity analysis aimed at identifying the most optimal configuration within the proposed design. The findings reveal that the suggested structure successfully achieves a notable reduction in torque ripple and radial force when compared to the traditional counterpart, albeit with an expected reduction in average torque. These features render the new topology particularly well‐suited for applications that prioritise noise and vibration reduction. Furthermore, the effectiveness of the proposed topology is corroborated through experimental tests, providing empirical evidence of its advantages and potential for practical applications. [ABSTRACT FROM AUTHOR]

Aiming at resolving the parameter uncertainty of the servo system under multi‐working conditions, a flatness‐based switched linear system model is proposed. Firstly, a fifth‐order linear switched discrete‐time system with uncertain parameters is established. The flatness properties of switched system is described and a de Bruijn's graph‐based framework is introduced for graphical description of the switched system. In addition, non‐linear bode diagrams are obtained via sweeping signals with multiple amplitudes. The discrete equations of the electromechanical servo system are established by the bode plots. The unknown parameters of the subsystems in switched model are identified by the simulated annealing algorithm, and compared with the least squares method to verify the accuracy of the identified parameters. Finally, the simulation model and experimental platform are constructed to verify the effectiveness of the proposed method. The switched model is compared with the classical transfer function model and single subsystems. The results indicate that the resolution of parameter uncertainty in servo systems is effective. The accuracy of the established switched model is about 99.5%. The accuracy of the switched linear system model of the electromechanical servo system is verified and the proposed modelling method is validated. [ABSTRACT FROM AUTHOR]

Harmonic magnetic gears (HMGs) have the advantage of lubrication‐free, high speed ratio and high torque density, which make it an attractive solution for safety critical applications. Due to eccentricity caused by machining and assembly, HMG suffers from dynamic eccentricity (DE) in operation, however, its effect on HMG performance is still unknown. Transmission characteristic of HMG under DE is studied. First, a magnetic equivalent circuit (MEC) model of HMG is proposed to build the magnetic coupling torque analytically, and the geometry of air gap is analysed parametrically to derive its equivalent reluctances. Flux density and coupling torque can be acquired by solving MEC equations. The accuracy of the MEC model is verified by finite element method. To study the transmission characteristic, an electromechanical coupling simulation framework for HMG is constructed, motion trajectories of rotors are investigated in case of DE, the output torque in locked‐rotor condition and speed response in continuous operation can be derived by simulation. It is found that torque ripples that have the same frequency with input rotor are induced by DE; the results are then verified in the experiment. This paper provides a theoretical guidance for the design and condition monitoring of HMG. [ABSTRACT FROM AUTHOR]

The authors present a new design of a PM‐assisted synchronous reluctance motor (PM‐SynRM) with uneven air‐gap length to improve the power factor and enhance the torque production capability. The rotor structure is modified to properly shift rotor magnetic poles and therefore (i) increases the back‐EMF and the electromagnetic torque, (ii) allows electromagnetic torque and reluctance torque components peak near the same current phase angle. The proposed solution is simple, does not require changing the arrangement of magnets and/or flux barriers and is applicable to all types of PM‐SynRMs. Sensitivity analysis is carried out to determine the extent of which the proposed magnetic pole shifting may impact the resultant torque profile. To assess the level of success, the electromagnetic characteristics of the proposed design (e.g. torque, power factor, and back‐EMF) are compared against the baseline structure under the same operating conditions. For verification purposes, Finite Element simulation results are validated via a series of analytical calculations and experimental measurements, and supported with detailed theoretical discussion. [ABSTRACT FROM AUTHOR]

The segmental translator linear switched reluctance motor (STLSRM) is a special type of linear switched reluctance motor (LSRM) that has more output power than its conventional type. Therefore, it can be a good choice for certain applications. Heat is one of the factors limiting the output in machines. Therefore, predicting the thermal distribution of machine is as important as the magnetic design. A comprehensive thermal model is presented based on the lumped parameter approach for STLSRM, which predicts temperature distribution in different parts of this motor, including slot winding, end‐winding, stator pole, stator yoke, and the moving part. Considering that the proposed thermal model depends on dimensions and materials used in machine, it can be used for other designs of the STLSRM. The presented thermal model is applied to a typical STLSRM and temperature is determined in its different parts. The simulation results are then compared with the results of 3‐D thermal modelling based on the finite element method (FEM) for validation. [ABSTRACT FROM AUTHOR]

Direct Instantaneous Torque Control (DITC) with an adaptive turn‐on angle technique is presented in this paper to improve the torque ripple of the Switched Reluctance Motor (SRM) for Electric Vehicle applications. Torque ripple suppression is achieved by employing two operating modes during the commutation interval. First, both the outgoing and incoming phase states are modified to track the required torque during the incoming phase's minimum inductance area. As soon as the incoming phase leaves its minimum inductance zone, the outgoing phase is demagnetised, and only the incoming phase state is modified for torque tracking. In addition, a closed‐loop regulator is used to dynamically control the turn‐on angle that drives the incoming current to reach its first peak at the instant of switching between the two operation modes when the rotor and stator poles initiate overlap, thus increasing the motor's efficiency. Simulation results showed that the proposed control method has superior advantages over the traditional DITC and Average Torque Controller. Furthermore, the simulation results were verified experimentally using a four‐phase 4kW, 8/6 SRM prototype. [ABSTRACT FROM AUTHOR]

This study proposes a space vector pulse width modulation (SVPWM) driving method for the switched reluctance motor (SRM), which enables the use of a standard full‐bridge power converter to drive a three‐phase SRM with a ring structure, in place of the traditional asymmetric H‐bridge (AHB). Based on this driving topology, the SVPWM approach is employed to drive the SRM, and its performance is compared with that of the conventional SRM driving method utilising the AHB. The findings indicate that the SVPWM method can effectively reduce torque ripple in the SRM. Moreover, the experimental validation performed to verify the proposed driving topology and method yields results that closely align with the simulated outcomes. [ABSTRACT FROM AUTHOR]

Doubly salient electromagnetic machine (DSEM) can constitute a competitive rugged starter generator (SG) system. But under the traditional startup control method, the field current is set to the rated value regardless of speed or load torque conditions, and the phase currents are controlled with standard angle commutation, bringing in large power loss as well as non‐negligible torque ripple. To overcome these shortcomings, based on the established DSEM power loss calculation model, a currents distribution strategy is proposed according to the obtained quantitative relationship between DSEM power loss and field current under multiple speed and load torque conditions. Then, to identify the load torque for practical implementation, a novel torque observer is designed based on back propagation (BP) neural network algorithm. Afterwards, to further improve the startup torque performance, currents distribution with advanced angle commutation (AAC) strategy is put forward, where the optimal advanced angle is selected from a 3‐D lookup table to achieve the minimal commutation torque ripple. Under the proposed control strategies, DSEM power loss as well as the output torque ripple are desired to be decreased, the simulation and experimental results on a 12/8‐pole DSEM prototype verify the correctness and feasibility of the proposed strategies under multiple operating conditions. [ABSTRACT FROM AUTHOR]

Switched reluctance machines offer a robust structure, inexpensive maintenance, and a low‐cost drive. However, they can suffer from low mean torque, low torque density, and high noise. Techniques such as offering the stator poles at each phase in the shape of a C core, adding several teeth to the two poles of each C‐core, and embedding permanent magnets to overcome these deficiencies are presented. Permanent magnets are embedded into the structure to create a hybrid excitation that provides a higher torque density. The C‐core stator modules of the stator are toothed to improve the torque. The radial forces on the shaft are balanced. The design procedure, operating principles, and performance trade‐offs are explained. Also, a magnetic equivalent circuit model is introduced. The model provides continuous relationships over the operating regions and incorporates core saturation and accurate flux tubes to attain high precision. Finite element models are also employed in the analysis and design process. The motor is prototyped, and experimental results are extracted, closely matching those obtained with the model and finite‐element analysis. [ABSTRACT FROM AUTHOR]

Here, the authors propose two new Permanent Magnet (PM) embedded linear switched reluctance motors; one is a modular linear hybrid reluctance motor (MLHRM), and the other one is a segmental linear hybrid reluctance motor (SLHRM). Both structures employ PMs between the side teeth of the modules/segments. The main contribution of the PMs is to increase the air‐gap flux density, which results in an enhanced thrust, and decrease the magnetic saturation in iron parts. The magnetic equivalent circuit model is used to demonstrate the positive effect of inserting PMs in the MLHRM and SLHRM compared to their PMless counterparts. The optimal pole number and design procedure are illustrated. The simulation results are obtained in terms of static thrust, flux linkage, flux density distributions, and steady‐state current and thrust. The results show that the proposed MLHRM and SLHRM offer a higher thrust and lower current compared to their PMless form. Also, the PMs decrease the root mean square (RMS) current under the steady‐state performance of the motors, in which a higher thrust is produced with a lower RMS current. Finally, the MLHRM and SLHRM are fabricated and the test results are obtained and compared with the simulations, which illustrate a satisfactory agreement. [ABSTRACT FROM AUTHOR]

This study elaborates upon a new modular split‐tooth permanent magnet‐assisted switched reluctance motor (MSTPM‐SRM). In the proposed topology, the stator comprises six modular E‐cores in which the middle poles are split into two teeth. Two permanent magnets (PMs) are placed between each module's middle and side poles. Primarily, the proposed topology is introduced. Next, the principle of operation of the proposed topology are elucidated, and the magnetic equivalent circuit analysis is adopted in order to validate the operational basics. It is proved that the embedded PMs significantly increase the air‐gap's flux density and adjusts the poles' flux density. The flux density distributions, static, and steady‐state characteristics of the proposed MSTPM‐SRM motor and its PMless counterpart are extracted by utilising 2‐D finite element analysis. It is illustrated that the average torque of the proposed MSTPM‐SRM is dramatically increased compared to its PMless counterpart, especially at high excitation currents. Furthermore, the cogging torque analysis is done and it is shown that the proposed structure has approximately zero cogging torque. Finally, a prototyping version of the proposed motor is fabricated, and the experimental results are elicited. It is shown that the experimental results endorse the simulation results. [ABSTRACT FROM AUTHOR]

A supply and demand balance control method for an electrical submersible linear motor utilised in offshore oil exploitation is proposed in this study. The permanent magnet linear motor is replaced by an electrical submersible linear motor based on switched reluctance linear motor. The sensorless control method further enhances the stability of the oil exploitation system. Meanwhile, a supply and demand balance control method is proposed to maintain the fullness of the submersible plunger pump within an ideal range. An established speed function allows the speed of the electrical submersible linear motor to dynamically alter in response to the change in oil deliverability and increasing the system's production. Additionally, maintaining the fullness of the submersible plunger pump within the ideal range helps simplify the model and increase computation accuracy. Finally, the supply and demand balance control method is validated and compared with the intermittent oil exploitation control method by simulations and experiments. Results from the simulations and experiments indicate that the proposed method can increase the production of the offshore oil exploitation system in addition to causing the motor to follow changes in oil deliverability and adjust the speed. [ABSTRACT FROM AUTHOR]

Fractional‐slot concentrated‐windings are appreciated for their simple construction, short end‐winding length, high copper fill factor, low cogging torque, good field‐weakening capability and fault‐tolerant ability. However, in comparison to the conventional distributed windings, the fractional‐slot concentrated‐windings are characterised with high space magnetomotive force (MMF) harmonics, which results in undesirable effects on the machine performance, such as localised core saturation, eddy current loss in the rotor and noise and vibration. In order to improve winding characteristics, several techniques have been developed recently. This manuscript introduces the 5 new winding topologies by using the general concept of stator slot shifting. It means that, in order to cancel undesirable MMF harmonics, by doubling (or tripling or even multiplying) the slot number and dividing the winding and then relatively shifting the winding by one (or more) slots, the undesirable harmonics have been eliminated effectively. The best choice is chosen according to the lowest amount of the MMF harmonic, highest value of winding factor and torque desirable characteristics. At the end, comprehensive comparisons for the designed synchronous reluctance motor (SynRel) equipped with proposed windings and also distributed winding are presented. The analytical study and 2D FEM analysis results show that it is possible to get an ideal low space‐harmonic winding topology, and consequently, a low torque ripple for these motors. [ABSTRACT FROM AUTHOR]

The strong coupling effect between the torque system and the suspension system of the single‐winding bearingless switched reluctance motor (SWBSRM) would result in continuous interference to the system and bring difficulties to the design of the control system. Moreover, strong external disturbances will further reduce the stability of the control system. To improve the anti‐disturbance ability and enhance the robustness of the control system of SWBSRM, a design method of the entire control system based on the second‐order sliding mode (SOSM) controllers is proposed. The strongly coupled SWBSRM torque system and suspension system are linearised and decomposed through the feedback linearisation method to benefit the design of SOSM controllers. Then, combined with a super‐spiral algorithm, the super‐spiral sliding mode controllers in the outer loop for torque and suspension system are designed separately. The design of controllers considers the interference caused by the coupling effect and the influence of external disturbance. The range of gain, which can ensure the finite time convergence of the control system is determined through proof of stability. Simulation and experiment results show that the second‐order sliding mode controllers have faster response speed and control precision when suppressing coupled interference and strong external disturbance. [ABSTRACT FROM AUTHOR]

Due to the high back electromotive force and short commutation time at high speed, the phase current of switched reluctance motor (SRM) is difficult to reach a large value, which limits the output performance of the motor in high‐speed operation. This paper proposes a novel multilevel converter (MLC) with fast excitation and fast demagnetisation capability, which allows each phase to control independently even in overlapping conduction operation and is suitable for SRM with any number of phases. The excitation current in the rising inductance region is increased by high‐voltage fast excitation, thus increasing the phase current level of the motor at high speed; the current tailing in the falling inductance region is suppressed by high‐voltage fast demagnetisation, thereby reducing the generation of negative torque. Based on the novel MLC, a maximum torque per ampere (MTPA) control strategy is designed, and closed‐loop control of the boost capacitor voltage is developed. By optimising control, the output torque and efficiency of switched reluctance motor drive (SRD) are greatly improved, and the constant power operation range is extended. Simulation study and experimental results verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

A torque sharing function (TSF) with online compensation of excitation current control method is proposed for torque ripple reduction in electric excitation auxiliary switched reluctance motor (SRM) drives, which mitigates the problem of severe torque ripple inherent in traditional TSF control during the commutation of armature winding. The torque formula of the motor is derived and the finite element analysis of the static torque under different excitation currents is carried out, which proves that the output torque can be changed by adjusting the excitation current. Therefore, the proposed method is based on cosine TSF control, which uses a sliding mode control algorithm to adjust the amplitude of the excitation current to online compensate the torque fluctuations during commutation. Besides, Simulink, Simplorer and Maxwell co‐simulation and experiments are carried out on the traditional TSF control and the proposed method. The results demonstrate that the proposed method is superior to the traditional TSF control and the electric excitation auxiliary SRM has better torque performance and smaller torque ripple under the proposed method. [ABSTRACT FROM AUTHOR]

This paper reports on a novel unipolar current excited control scheme for the asymmetric bridge converter (ABC)‐based switched reluctance drive (SRD), where the 3D space vector modulation under three modes is developed to reduce the total harmonic distribution (THD) and torque ripple. Firstly, two different 3D vector distributions, namely, the small voltage amplitude mode and large mode are presented based on the asymmetric converter. For both distributions, the zero‐sequence voltages generated by the effective vectors are considered. Additionally, zero‐sequence vectors (1,1,1) and (−1,−1,−1) are no longer treated as null vectors and involved in the control of zero‐sequence current. Then, the duty cycles of both two modes are obtained by the combination of the zero‐sequence and two adjacent active vectors. Moreover, based on the large modulation mode, a novel method combined with the small mode is proposed to further optimise the switching costs and torque ripples. The effectiveness of the proposed modes is verified through the simulation in MATLAB and the experiment on a dSPACE‐1103‐based prototype. Compared with the conventional switched reluctance motor vector control, the proposed scheme delivers better performances of THD, efficiency and torque ripple reduction. [ABSTRACT FROM AUTHOR]

This paper investigates the accuracy of rotor‐locked transient‐response (RLTR)‐based vibration model for switched reluctance machines (SRM). RLTR is stator vibration stimulated by abrupt change of radial force when turning off one phase of SRM with rotor being locked, the total vibration of SRM can be modelled as linear superposition of RLTR series. An electromechanical model is built to clarify the generation of SRM vibration, it is revealed that some velocity‐depend terms in electromechanical model would be neglected when rotor is locked, it leads to inevitable difference of RLRT between rotor‐locked condition and rotational condition, the difference is illustrated through multi‐physics simulation. A harmonic radial force model is proposed to quantitatively evaluate the accuracy of RLTR‐based vibration model, radial force spectrums with locked rotor and rotational rotor are compared to predict relative error between RLTR‐based vibration and actual vibration. The influence of turn‐off angle and velocity on accuracy of RLTR‐based vibration model is also analysed. The accuracy of RLTR‐based vibration model is evaluated through experiment on 3‐phase 12/8 SRM, the results showed that: (1) the accuracy of RLTR‐based vibration model is impacted by turn‐off angle and velocity; (2) relative error between RLTR‐based vibration and actual vibration can be predicted using harmonic radial force model. This paper illustrates the generation mechanism of modelling error for commonly used RLTR‐based vibration model of SRM, the proposed error prediction method could lead to improved accuracy on SRM vibration model through error compensation. [ABSTRACT FROM AUTHOR]

This paper presents an analytical modelling technique based on modified winding function and co‐energy analysis, for characterisation of synchronous reluctance machines, in conjunction with a hybrid algorithm for mapping of the machine's operating point on BH curve and the corresponding performance parameters in non‐linear magnetic condition. The model successfully provides the mean torque and the torque profiles of a synchronous reluctance motor as a function of input current and load‐angle in the magnetic linear and non‐linear conditions. The obtained results of this proposed model are compared with finite‐element‐analysis (FEA) based commercial design software Simcentre‐MAGNET. The comparison proves this model's capability to estimate the machine's performance parameters with considerable accuracy from an already established design analysis technique, FEA. The proposed modelling technique requires only a fraction of simulation runtime when compared to other design analysis techniques. Considering the accuracy of this modelling technique and the least requirement of computation resources and simulation time, this model can be used as an initial iterative‐design tool for mass personalised, additively manufactured electrical machines where rapidness of the iterative design analysis tool is of paramount importance. [ABSTRACT FROM AUTHOR]

A linear switched reluctance motor (LSRM) is designed for electric propulsion application in a Magnetically Levitated (Maglev) train with the base speed of 7.6 m/s and operating at a maximum of 27.8 m/s. In such high‐speed LSRMs, windage loss is one of the key issues of concern. Usually, windage loss accounts for approximately 0.5% below the base speed, 20% above the base speed, and 45% at higher speeds of the total loss of the LSRM. One of the many parameters affecting this windage loss is the stator slot profile. This research work studies about different stator slot structures, thereby aiming to reduce the windage loss through computational fluid dynamics analysis. Furthermore, experimental testing of the LSRM is also done to verify the simulation results. [ABSTRACT FROM AUTHOR]

To accurately predict motor performance, considering the effects of core losses is of great importance, especially at speeds much higher than the base where the core losses represent a considerable portion of the total drive losses. Neglecting the effects of core losses leads to an error in the switched reluctance motor (SRM) performance prediction. In this study, a previously developed non‐linear SRM model with multiphase coupling is extended by considering the instantaneous effects of core losses on the SRM performance. Using the new model, the nature of these effects is determined. A comparison of the simulation results of the proposed, basic, and finite element method (FEM) model confirms the importance of considering the effects of core losses on motor performance. Besides the FEM model, the accuracy of the proposed model is verified by experiments. [ABSTRACT FROM AUTHOR]

The modelling and analysis of Brushless Doubly Fed Reluctance Machines (BDFRMs), taking into account magnetic saturation and rotor movement, by conventional modelling techniques are very difficult, if not impossible, because the two stator windings have different number of poles leading to a complex flux pattern. To overcome this drawback, Finite Element Analysis (FEA) is generally used for modelling and analysing BDFRMs. But it requires a considerable computational time compared with semi‐analytical methods. This article, therefore, steps forward by proposing a new approach to dynamical modelling of BDFRM based on the Reluctance Network Method (RNM), which can enable accurate calculation of the electromagnetic parameters and performances of BDFRMs. Indeed, the reluctance network method offers an interesting compromise between precision and computation time compared to finite element analysis. To validate the proposed model, simulations are carried out and comparison are made with FEA. It is observed that the greatest error between the values of the proposed model and those from FEA is close to 1%. The accuracy in the calculation of electromagnetic parameters, as well as the computational time leads us to the conclusion that the proposed model could be suitable for optimisation and control purposes. [ABSTRACT FROM AUTHOR]

To obtain a short flux path and improve the torque performance, a double‐phase excitation (DE) was generally used for switched reluctance motor (SRM). But the torque ripple of the SRM working under DE with traditional winding distribution increases because of the inconsistent electromagnetic field. To deal with this problem, an 8/6 SRM working under DE with novel winding distribution (DESRM) is proposed here. In order to comprehensively analyse the electromagnetic performance of DESRM, it is compared with a traditional single‐excitation SRM and double‐excitation SRM with traditional winding, in terms of air flux density, radial and tangential force components, inductance, torque, and losses. The theoretical and finite element analysis results reveal the cause of differences on torque and vibration of the motor as well as the mechanism of generating different motor performance. In addition, the analysis shows that the proposed DESRM generates a higher torque with a reduced torque ripple. Finally, a pair of prototypes with different winding configurations is designed and used to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

A permanent magnet synchronous motor (PMSM) is introduced with 120° phase belts toroidal windings (PBTWs) (120°PBTWPMSM), in which its armature reaction field principle is elaborated. Then, the experiment concerning the 120°PBTWPMSM is conducted to verify the validity of the related analysis and the feasibility of the 120°PBTWPMSM. In addition, a method of shifting the magnetic poles (SMP) is adopted to suppress the cogging torque and the torque ripple. After this, the 120°PBTWPMSM after SMP is further optimised by the Taguchi method to obtain the structural parameters of the motor with optimal comprehensive performance. Finally, the performance of the original motor, the 120°PBTWPMSM after SMP and the optimal motor are compared, which verify the effectiveness of the optimization methods. [ABSTRACT FROM AUTHOR]

A new semi‐analytical expression is presented based on two integrations for calculating the magnetic force of a solenoid inductor wound by rectangular cross‐section wire. The authors simplified the solenoid inductor coil to a collection of circular coils, and the current density of the coils in the radial direction which was inversely proportional to its radius is considered. The obtained expressions can be implemented by adaptive Gaussian quadrature integration with MATLAB programming. In addition, they used the filament method and the finite element method to calculate the magnetic force on the solenoid inductor coil. The correctness of the semi‐analytical expressions was verified by comparing the results of the semi‐analytical numerical method with those of the filament method and the finite element method, respectively. The derived semi‐analytical expressions of magnetic force allow a low computational time compared with the filament method and the finite element method to a specific accuracy. The calculation results show that: the solenoid inductor coil tends to compress in the axial direction, and the axial magnetic force on the outermost coils is the largest; the solenoid inductor coil tends to expand outward in the radial direction, and the radial magnetic force on the intermediate coil is the largest. [ABSTRACT FROM AUTHOR]

Here a new sensitive fault detection criterion is proposed, based on the stationary wavelet transform (SWT) decomposition components of the stator currents, for the online detection of stator winding turn‐to‐turn faults at an early stage of development. The energies of the desired detail components are calculated and the normalized Euclidean distance of the energy differences between the three phases is used as a new fault detection criterion. The robustness of the proposed technique against the presence of rotor turn‐to‐turn faults and loading variations is demonstrated. In addition, an adaptive threshold level as a function of the voltage unbalance factor is proposed to guarantee the robustness of the diagnostic technique against unbalanced voltage sources. Experimental results demonstrate the effectiveness and sensitivity of the proposed diagnostic approach for the detection of stator faults in line‐connected and inverter‐fed motors. [ABSTRACT FROM AUTHOR]

Asymmetrical rotor topologies were previously proposed for synchronous reluctance motors (SynRM) to reduce the torque ripple. However, potential negative effect of these topologies on mechanical vibration, which is often serious in SynRM, was hardly studied and such an effect is investigated here. An analytical model is established, through which the spatial orders of the radial electromagnetic force with various rotor topologies are derived, and the relationship of the peak frequencies and the corresponding spatial orders in the radial electromagnetic force is revealed. It is shown that some asymmetric rotor topologies will reduce the order of the lowest spatial harmonic for the radial electromagnetic force, and consequently increase the vibration. Finite element analysis and experiments demonstrate the same results. Finally, a specific rotor topology with asymmetry about both d‐axis and q‐axis is recommended, which can reduce the torque ripple, but would not deteriorate the radial electromagnetic force and vibration. [ABSTRACT FROM AUTHOR]

This article investigates the effect of utilising rotor conducting screens within a switched reluctance machine (SRM). Conducting, non‐magnetic materials such as aluminium or copper are inserted into the interpole regions of the rotor. The effective unaligned inductance decreases, which increases the conversion area allowing the machine to develop more power. Predicting machine performance implies knowing the value of the unaligned inductance. A procedure for calculating the effective unaligned inductance for screened motors using the flux tube method is presented. Finite element analysis results establish the validity of the proposed calculation method. A detailed design procedure for screened SRM is presented. [ABSTRACT FROM AUTHOR]

Switched reluctance motors (SRMs) are considered as a potential candidate in many high‐reliability demanding applications, including electrical vehicles (EVs), hybrid EVs and more electric aircrafts. For precise and stable control performance, normally an SRM drive requires one current sensor for each phase winding. Failure of any of these sensors will inevitably degrade the system's performance. The behaviour of an SRM drive under current sensor failure is investigated and a fault‐tolerant control technique is proposed by changing the current sensor installation scheme without adding extra current sensors. Moreover, through the analysis of the detected currents by the phase current sensors and the dc‐link sensor, a diagnostic scheme for current sensors failure is presented. The excitation current in the faulty phase under postfault conditions is reconstructed through a simple calculation without injecting a high‐frequency signal or modifying the switching signals, thereby reducing the current distortion and avoiding voltage penalty issues. Motor drive can operate with satisfactory control performance even when all the phase current sensors are in fault conditions. Detailed analysis under both steady state and dynamic conditions through thorough simulations and experiments has been carried out on a three‐phase 12/8 SRM. The extensive results validate the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

Here, the authors present a new constrained multi‐objective optimization method for maximizing output power and efficiency of switched reluctance motor (SRM). The constraints play a significant role in this process. Artificial neural network‐based models are created to represent the SRM behaviour which is a difficult task. For this reason, a single neural network for each objective is built and the number of training data has been increased to reach a good accuracy. The authors propose a neural network‐based adjoint Lp metric technique to combine several objective functions and constraints with different weight factors to a single function which should be minimized. To apply the constraints, an adjoint term is added to the original Lp function including only objective functions. The flux densities of the magnetic materials are selected as the optimization constraints. When approaching as close as possible to the saturation level, the SRM has a better performance. Adding an adjoint term to the original Lp leads to better optimization results which were proved by comparing with a conventional optimization. Also, all obtained results were finally validated by the Ansoft Maxwell software. [ABSTRACT FROM AUTHOR]

This study proposes a state formulation of the space‐vector dynamic model of the Synchronous Reluctance Motor (SynRM) considering both saturation and cross‐saturation effects. The proposed model adopts the stator currents as state variables and has been theoretically developed in both the rotor and stator reference frames. The proposed magnetic model is based on a flux versus current approach and relies on the knowledge of 11 parameters. Starting from the definition of a suitable co‐energy variation function, new flux versus current functions have been initially developed, based on the hyperbolic functions and, consequently, the static and dynamic inductance versus current functions have been deduced. The dynamic inductance functions have been derived so to fulfill the reciprocity conditions. This study presents also a technique for the estimation of the parameters of the proposed magnetic model, which is based on stand‐still tests without the need to lock the rotor. The identification process has been performed based on the minimization of a suitably defined error function including the difference between the measured and estimated stator fluxes. The proposed parameter estimation technique has been tested in both numerical simulation and experimentally on a suitably developed test set‐up, permitting the experimental validation of the proposed model. [ABSTRACT FROM AUTHOR]

The magnetic effects and consequently the radial force are the main causes of noise in switched reluctance motors (SRMs). In this study a new design for SRM is developed in order to reduce acoustic noise. In this research a new design for SRM is developed in order to reduce the acoustic noise. In this investigation, at first, different SRM structures are simulated using JMAG software. An 8/6‐pole SRM is designed and built with special modification in the rotor and stator structures. For increasing mechanical strength, trapezoidal stator and rotor pole shape with poles arc βr = βs = 21° are proposed. In this design the taper angles of stator and rotor poles are equal. For noise reduction, the mechanical restructuring is done according to stress analysis. The new designed SRM are simulated and tested experimentally under no‐load and full‐load conditions. The results are shown and compared. Comparison between these results and the results of other structures shows that the acoustic noise of the newly designed motor is reduced considerably. The results show an acoustic noise reduction of ∼72% in new structure SRM. [ABSTRACT FROM AUTHOR]

The rotor structure of synchronous reluctance motor (SynRm) is usually provided with redial ribs to improve structural ruggedness for high‐speed operation. While these radial ribs contribute to mechanical robustness, they also reduce the average torque and limit the flux‐weakening capability due to an increase in inductance along the q ‐axis. To address this issue, the rotor design is refined by adopting non‐magnetic radial ribs in this study. The introduction of titanium as non‐magnetic material for radial ribs prevents magnetic leakage flux from flowing along the q ‐axis, and thereby improves the average torque, saliency ratio, efficiency and power factor of the SynRm. Furthermore, along with the electromagnetic analysis, the mechanical integrity of the proposed rotor design is also investigated. Two prototypes rated 1 kW at 1500 rpm are fabricated using both the conventional and the proposed rotor design, while the stator and other parameters are maintained constant in the two cases. The conventional design uses magnetic radial ribs whereas the proposed design uses non‐magnetic radial ribs. Finally, a thorough comparative study, including inductance tests on the prototypes, is performed between the proposed and the conventional SynRm, confirming the strengths of the technology solution being set forth. [ABSTRACT FROM AUTHOR]

A comprehensive study on divided‐teeth permanent‐magnet assisted outer‐rotor switched reluctance motors (SRMs) is carried out. Foremost, it looks into the impact of the number of teeth per stator pole. The average and maximum torque profiles of the compared structures are obtained using finite‐element simulations. It is shown that as the number of teeth increases, higher torque is obtained. Then, six small PMs are inserted inside the teeth of neighbouring modules to form new hybrid reluctance motors (HRMs). The four permanent‐magnet assisted SRMs are compared in terms of the average and maximum torques using finite‐element simulations. Based on the comparison results, the 48/50 HRM is selected as the best candidate among all compared SRMs and HRMs. The magnetic flux density distributions, static torque, and flux linkage characteristics of the proposed HRM are obtained. Moreover, the cogging torque profile of the motor is obtained, which approximates to zero. Next, the steady‐state performances of the proposed HRM are obtained under low‐ and high‐operating speeds. Finally, a prototype of the machine is constructed and the test results are obtained and compared with those of the simulations, which show that there is a good agreement between these results. [ABSTRACT FROM AUTHOR]

Based on a four‐phase 8/6 structure switched reluctance machine for electric vehicles, the influence of different magnetic pole distributions on iron loss and temperature field is studied here. Firstly, by fitting the core silicon sheet iron loss data of the prototype, a mathematical calculation model of switched reluctance iron loss is constructed. Then, in order to analyse the flux density waveform of the iron core, a 2D finite element model is proposed. Under different magnetic pole distributions, the magnetic flux densities of the iron core are compared and the iron loss is calculated as well. Finally, the simulation results are obtained by establishing the 2D finite element thermal model of the prototype and analysed. Then, the experimental test platform is built and experimental data are recorded and analysed. By comparing the experimental results, it is found that the temperature rise is well consistent with the temperature rise of the 2D finite element thermal model. [ABSTRACT FROM AUTHOR]

The multi‐layer switched reluctance motor (SRM) is a special type of the SRM which can be utilised appropriately in high‐power applications such as electric vehicle (EV). Thermal modelling of the multi‐layer SRM is considered for the first time in the present study and a lumped parameter thermal model is introduced for quick prediction of temperature rise in this motor. In the introduced lumped thermal model, independent thermal networks are considered for different parts of the machine including frame, stator yoke, stator pole, winding, air‐gap, end‐winding, end‐cap air, rotor pole, rotor core and shaft. All details of the modelling and the required equations are given and therefore someone can use the model easily. The developed thermal model is applied to a typical two‐layer 8/6 SRM and a prototyped three‐layer 8/8 SRM and the simulation results are then compared with those derived from three‐dimensional finite element (FE) method using ANSYS FE package and experimental results. These comparisons show well high computation speed and accuracy of the lumped thermal model developed for the multi‐layer SRM. [ABSTRACT FROM AUTHOR]

Changes in inductance profiles of motors from originally designed values are observed due to manufacturing defects and different measurement techniques adopted. This introduces changes in the magnitude of voltage dip that could be tolerated by a synchronous reluctance motor operating at a particular speed and torque while being connected to a weak grid. Since the voltage dip margin is dependent on the inductance of the motor, it changes as per the variations in inductance. This paper proposes a novel methodology to analyse the variations in the voltage dip margin as per the discrepancies in inductances when the motor drive is expected to deliver a particular speed and torque. A control strategy is also proposed to mitigate the ill‐effects of the voltage dip by changing the operating point of the motor. Mathematical expressions are derived showing the voltage dip margin for different degrees of variations in the inductances. It is observed that with reduction in the inductance value, the voltage dip margin increases with increased current, where the current still remains within the maximum current limit of the motor, while the motor is forced to deliver the same speed and torque. The proposed mathematical derivations are validated through simulations and experiments. [ABSTRACT FROM AUTHOR]

This study presents the principles of analytical lumped parameter model for a synchronous reluctance motor (SynRM) for traction application purposes. Particular focus is put on the calculation of the heat transfer from the machine's housing during the active and passive cooling. For this purpose, the area‐based composite correlations method is proposed. The approach is attractive due to its simplicity and the fact that it closely models the temperature of the machine's housing. Finally, the proposed thermal model is evaluated experimentally on a totally enclosed fan cooled SynRM, and good correspondence between the analytical and experimental results is obtained. [ABSTRACT FROM AUTHOR]

In this work, a new elevator system created by a linear switched reluctance motor is presented. Unlike conventional linear motors, the proposed linear motor has more than one translator. Each phase in a translator generates a pulsing force; hence, the total generated force has noticeable ripple making it difficult to soft motion. In order to solve this problem, similar phases in different translators have been located in positions with specified distances together. As a result, similar force pulses would be shifted so that they can compensate together. An appropriate control strategy has been designed for the system, which can control the current, force, speed, and position simultaneously. A conventional proportional–integral controller and an adaptive fuzzy controller have been used to control the speed. In order to have a precise study, a prototype elevator system along with its control unit has been made and the obtained results have been compared with the simulation results. These results confirm that the proposed structure can significantly produce force and speed ripples. [ABSTRACT FROM AUTHOR]

In order to reduce the torque ripple for switched reluctance motor (SRM), the learning error preprocessing‐based torque–flux linkage recurrent neural network adaptive inversion control (TFRNNAIC) for SRM torque is proposed by the filter preprocessing and the non‐linear mechanism characteristics for SRM. In TFRNNAIC with the advantages of parallel and series–parallel structure, the torque feedback error learning method is employed to update the weights of the torque–flux linkage recurrent neural network. To suppress the ripple effectively in torque error used for the weight learning of the torque–flux linkage recurrent neural network and obtain an accurate TFRNNAIC, namely the torque–flux linkage model for SRM, the low‐pass filter preprocessing for the torque error is used. Moreover, the other low‐pass filter is executed to reduce the ripple in the output for the PD torque control. The superposition of outputs for TFRNNAIC and PD torque control is taken as the reference flux linkage. Compared with other control strategies, such as the classical parallel neural network control, the classical series–parallel neural network control and TFRNNAIC, the simulation results show that the learning error preprocessing‐based TFRNNAIC for SRM torque is capable of effectively reducing the torque ripple for SRM with the good recurrent performance. [ABSTRACT FROM AUTHOR]

To reveal the torque ripple mechanism of switched reluctance motors (SRMs), an analytical instantaneous torque model considering current harmonics is established based on the analysis of the air‐gap magnetic field. The results show that torque ripple contains third‐order harmonic components in a three‐phase SRM and mainly comes from the current harmonic, the rotor slotting, and their interaction. Then, the influence of main current harmonics on the torque ripple is investigated based on an analytical calculation method and it is found that the filtering of the second‐order current harmonic is more conducive to reducing the torque ripple. Finally, the influence of the turn‐on/turn‐off angle on each harmonic current is fully analysed by means of the analytical modelling of current, based on which the second‐order current harmonic and torque ripple is reduced by optimising the turn‐on/turn‐off angle. Also, it is found that the suitable prior turn‐on angle and delayed turn‐off angle is helpful to reduce the torque ripple. [ABSTRACT FROM AUTHOR]

Aiming at the problems of severe vibration of switched reluctance motor (SRM) and the transfer of the peak vibration caused by newly produced radial magnetic force under static eccentricity (SE), this study proposes a vibration reduction method for SE. First, the analytical relationship between the radial magnetic force harmonics and the current harmonics is derived. 2D Fourier decomposition is used to analyse the temporal–spatial characteristics of force harmonics and the vibration response under SE. Then the expression of the force harmonic, which causes the peak vibration, is used as the optimisation function of current harmonics. According to the analyses in this study, it is difficult to consider vibration reduction and torque simultaneously by single‐order current harmonic optimisation and the unreasonable optimisation range of current will seriously affect the output performance. Therefore, a reasonable optimisation range is set based on the above conclusions and the first five order current harmonics are optimised to improve the effect of vibration suppression further. The results of the finite element simulation verify the effectiveness of this method. [ABSTRACT FROM AUTHOR]

A new adaptive control strategy for a double‐sided linear switched reluctance motor is proposed in this work. Switched reluctance motors inherently have non‐linear dynamics that complicates their analysis and control. The Takagi–Sugeno fuzzy logic system has been used in this work to achieve an appropriate adaptive control system for the proposed linear motor. The fuzzy system has been heightened by non‐linear rule consequences and a time‐varying parameter. Updated laws have been designed to refresh the amount of the parameter consequently the suggested control system shows a stable performance in control of switched reluctance motors. The proposed control strategy is independent of the uncertainties of the motor dynamics and has an acceptable adaptability. This control method along with a conventional fuzzy logic based system have been studied on the proposed linear switched reluctance motor and their performances were compared in different performance conditions. An appropriate evaluation method has been used to compare the obtained results. The efficiency of the proposed method in different velocity commands has been examined and confirmed using appropriate simulation and experimental results. [ABSTRACT FROM AUTHOR]

Some key features to be satisfied by electric motors catering a wide range of applications are high specific power, lower manufacturing cost, rugged construction, and fault‐tolerant operation. Switched reluctance motor is one such motor technology satisfying all the above requirements and is an emerging competitor to the induction and permanent magnet motors in domestic, industrial and electric vehicle applications. The present‐day research on this motor is moving towards improving efficiency at lower speeds, power density, and the torque density. Certain challenges in achieving the same are (a) minimising the losses, (b) mitigation of torque ripple, noise, and vibration, and (c) material advancements. A review based on the estimation and mitigation techniques of each of these over the past three to four decades has been dealt with in this study. The salient features and results in each section provide a clear understanding of how each of these challenges can be overcome in the aspect of design and control strategies. [ABSTRACT FROM AUTHOR]

Flux saturation of switched reluctance motors (SRMs) and severe non‐linear relationship between current, position angles and electromagnetic torque lead to the difficulty of torque modelling and analysis. Specifically, the permeability of ferromagnetic material varies with the magnetic field strength H, and the core saturation effect increases with H. In this study, piecewise curve fitting method is adopted for analysing the relationship between the permeability and the stator winding current. The magnetic equivalent circuit method is adopted to build an analytical model for a SRM where the saturation of ferromagnetic material is expressed in the form of variable permeance. The comparison between computation results of analytical model and finite‐element method simulation results verifies the correctness of the proposed model. Simulation and experimental research of a SRM speed control system verify the practicability of the model. [ABSTRACT FROM AUTHOR]

In this study, a DC‐biased sinusoidal excited control method is proposed for a traditional four‐phase switched reluctance motor (SRM). Based on the proposed method, the torque ripple is smaller than that of traditional square excitation. First, the mathematical model of four‐phase SRM with DC‐biased sinusoidal excitation in dq‐axis rotating coordinate system is established and the instantaneous torque is analysed. It is found that the torque is proportional to q‐axis current and does not contain reluctance torque component with DC‐biased sinusoidal excitation for four‐phase SRM. Then the current control methods for torque component and magnetic field component are studied. The torque component is controlled by the sinusoidal pulse‐width modulation (PWM) method, and the magnetic field component is controlled by the current hysteresis tracking method. Finally, the proposed method is verified by finite element simulation and experiment results. Compared with the square wave excitation, the torque ripple is reduced by about 40%. [ABSTRACT FROM AUTHOR]

The longitudinal end effect (LEE) has a negative influence on the performance of the flat‐type switched‐reluctance linear machines (SRLMs). For example, it can give rise to the imbalance of peak currents of different phases and the aggravation of the force ripple. This study proposes a modified current estimation model and an adaptive adjustment method (AAM) of turn‐on position to compensate for the LEE of SRLMs. The modified current estimation model considers not only the self‐inductance characteristics but also the mutual inductance characteristics. Some simulation results demonstrate that this modified estimation model has better estimation accuracy than a previous one. Then, the AAM of turn‐on position is proposed based on this modified current estimation model. It can balance the peak currents of different phases so that the negative impact of the LEE is greatly reduced. This new control method is easy to implement and requires little test, and its effectiveness in compensating for the peak currents and reducing force ripple is experimentally verified. [ABSTRACT FROM AUTHOR]

This study proposes a modified structure of the E‐core permanent magnet (PM) assist switched reluctance motor by relocating the PM blades inside the stator core. For this purpose, the PMs are removed from the stator poles and placed slantwise inside the yoke. The proposed yoke‐PM assist structure is characterised with higher average torque and a lower torque ripple with respect to the conventional pole‐PM assist structure. An analytical approach based on the magnetic equivalent circuit is applied at the preliminary design stage to predict the performance of the motor. Based on the presented analytical modelling, the physical dimensions of the motor are optimised via a genetic algorithm to maximise the motor torque and the overall steady state performance. For further verifications, the finite‐element analysis simulation results are verified by the experimental tests on the motor prototype. [ABSTRACT FROM AUTHOR]

To reduce torque ripple of switched reluctance motor (SRM), a low‐torque ripple control method based on current vector is proposed in this study. In which, id=0 control strategy is adopted. Then, iq is decomposed into the vector sum of two‐phase currents in different positions. A Fourier series model about Te and iq is established and this model satisfies the magnetic saturation condition. According to the established Fourier series model, the change rule of iq based on constant reference torque is obtained. In this study, torque models of SRM under traditional unipolar sinusoidal excitation control method, constant iq unipolar excitation control method and variable iq unipolar excitation control method are analysed. Finally, experimental platform of SRM control system based on TMS320F2812 is built. Experimental results show that the variable iq unipolar excitation method based on current vector decomposition can effectively reduce the torque ripple of SRM. [ABSTRACT FROM AUTHOR]