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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]

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]

This paper presents an evolutional topology optimization of electric machines, which works like gradient‐based local search methods, based on the covariance matrix adaptation evolution strategy (CMA‐ES). The present method enables to improve the performance of initial machine shapes without computing the deviation of the objectives. Moreover, for the resultant shapes obtained by the present topology optimization method, this paper also presents a sensitivity analysis method based on the normal distribution which is used to seek for solutions in CMA‐ES. Using the present sensitivity analysis method, important parts which contribute to improve a machine characteristic can be visualized. The two present methods are applied to the optimization problem of a synchronous reluctance motor. It is shown that initial rotor shapes defined by designers can effectively be modified using the present optimization method. Moreover, it is also shown that the sensitivity distributions with respect to some machine characteristics are visualized by the present method. In addition, each machine characteristic is respectively improved by modifying the machine shape according to the respective sensitivities. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [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]

In this paper, we propose a novel multi‐objective topology optimization with response surface approximation interpolating various topologies, which is derived by deep learning with training data in the actual design space. The response surface is constructed by means of autoencoder with the training data of geometrically diverse shapes of targeted devices, which can express the interpolations that combine the multiple characteristic structures. The global topology search is performed based on the gradient information of the response surface, by which we can obtain the initial shapes for level set optimization to efficiently obtain easily manufactured and excellent Pareto optimal solutions. The effectiveness of the proposed method is demonstrated by optimizing multi‐flux barriers in a synchronous reluctance motor for the objective functions of average torque and torque ripple. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [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]

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]

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]

In this article, a 16/6 bearingless switched reluctance motor (BSRM) with segment hybrid rotor teeth has been presented. To realize the decoupling control of torque and suspension force, the rotor teeth were divided into three torque teeth and three suspension teeth, and both of them are embedded in support part. First, both torque and suspension force are generated by short‐circuit excitation, the flux linkage coupling between torque windings and suspension windings was eliminated, and the separate control of torque and suspension force was achieved. Then, by increasing the pole arc of suspension teeth, the inductance of suspension windings is kept constant, which eliminates the influence on the output torque when adjusting suspension force. Finally, the coupling degree is further reduced by using nonmagnetic material as the supporting part. In addition, to achieve a greater output torque, the torque teeth are processed into U‐shape and optimized the pole arc of stator teeth and rotor teeth. The characteristics of inductance, flux linkage, and output torque are analyzed by the finite‐element method, and the results show that the proposed structure basically achieves the decoupling control of torque and suspension force. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Switched reluctance motor (SRM) and induction motor (IM) technologies are studied based on specific ASEAN Bangkok and Hanoi driving cycles. Range simulations and thermal analyses have been performed on standard driving cycles: ECE15 and WMTC Part 1 as well as ASEAN cycles: Bangkok driving cycle and Hanoi motorcycle driving cycles. The e‐scooter ranges vary from 44 to 99 km depending on driving cycle, motor technology, and number of passengers. Finally, prototypes of both motors are manufactured and tested on a high‐speed test bench. Some experimental results are reported in this paper. As a conclusion, despite differences in terms of performances, cost, and range, both drive systems are, however, suitable for electric scooter application. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This study presents the operation of a synchronous reluctance motor drive under a sustained voltage dip condition while being connected to a weak grid. In the presence of an input voltage dip, motor may not be able to produce sufficient torque and maintain its original speed. A new technique is proposed in this study to maintain the desired reference torque and speed during a sustained voltage dip. The proposed technique is realised by evaluating mathematically the motor's allowable voltage dip margin corresponding to an operating point pertaining to a particular torque and speed in the current locus diagram of the motor. With prior knowledge of the voltage dip margin for every operating point in the current locus diagram, it would be possible to retain the same reference torque and speed by moving to a new operating point, which can be with lesser or greater id as compared to the initial operating point, in case a voltage dip greater than the tolerable margin occurs. To start with, voltage dip margin has been derived theoretically and the operation of the motor is investigated by deliberately introducing a voltage dip. The proposed methodology has been verified through simulations and experiments in this study. [ABSTRACT FROM AUTHOR]

Accurate rotor position is necessary for the control of switched reluctance motors (SRMs). Generally, three position sensors are ideally installed 120 electrical degrees apart for three-phase SRMs. However, the placement of position sensors may be inaccurate, particularly in small-size SRMs, and there is no method reported to deal with this problem up to now. Firstly, the position signals and the influence of the misaligned sensors on the detected rotor position are investigated. Then a novel method is developed to identify the misaligned position sensors with dynamic time warping (DTW) algorithm. The DTW distance versus the misaligned angle is calculated, and the relationship between them is described with linear regression analysis algorithm. Then the rotor position tolerant detection method is realised by compensating the misaligned angle in real time. Finally, comparative experiments are carried out on a three-phase 12/8 SRM drive system, and it can be found that the proposed strategy is capable of providing an accurate rotor position for the SRM drive system. The presented method is easy for online implementation and can be integrated into the control system conveniently. [ABSTRACT FROM AUTHOR]

This study proposes a model-based control strategy for flux weakening operation of a synchronous reluctance machine, with a methodology that is extendible to any synchronous machine. The strategy leverages in the presence of digital non-linear models that describe the relation between currents and flux linkages in the machine. Such models are usually needed for conventional maximum-torque-per-ampere control and sensorless control, but here they are exploited to achieve flux-weakening operation without the need of flux weakening regulators, ensuring a seamless transition between the operating regions of the machine. The external voltage regulation loop for flux weakening is thus eliminated and substituted by a combination of look-up tables and binary searches, which are executed within one digital control period and which generate the required current and voltage references that fulfil the drive limitations. The method can also be coupled with mechanisms to compensate for magnetic parameter inaccuracies, to achieve an accurate tracking of the reference torque. The proposed solution is simulated and validated in a laboratory test bench on an 11 kW synchronous reluctance machine. [ABSTRACT FROM AUTHOR]

In the traditional bearingless switched reluctance motor (BSRM) system, the electromagnetic coupling between the torque system and suspension system is unavoidable. In this Letter, the present BSRM has the advantages of electromagnetic decouple with independent torque-suspension magnetic circuit design. However, the further in-depth study shows that the BSRM has an obvious suspension force fluctuation according to its asymmetry structure. Thus, it is necessary to build an accurate suspension force mathematical model considering commutation ripple. In this frame, a magnetic field segmentation method is proposed and the accurate suspension force model is built with Maxwell stress method and its reliability and precision are verified, modified based on finite element analysis. [ABSTRACT FROM AUTHOR]

This study introduces an optimisation-based procedure for characterising switched reluctance machine (SRM) performance and studies the optimisation to determine the conduction angles in SRM drives. The objectives employed in the optimisation cases are maximising average output torque, maximising the ratio of average torque over root mean square (RMS) value of phase current, and minimising RMS value of net torque ripple. Combinations of these objectives are used in four different cases, which are formulated either as single- or multi-objective problems. These cases are then compared in terms of output torque, torque ripple, and efficiency. One method of the four is selected and the performance of the motor over the entire operating range is characterised based on optimised turn-on and turn-off angles. Experimental results are used to verify the motor performance obtained from the optimisations for selected operating points. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the recent technical trends in permanent magnet synchronous motors (PMSMs), especially the rare earth (RE)-less PMSMs that have been developed in Japan. The RE-less PMSMs, along with PMSMs with reduced RE permanent magnets (PMs), PM-assisted synchronous reluctance motors (PMASynRM) with ferrite PMs, spoke-type interior PMSMs (IPMSMs) with ferrite PMs, and axial-gap PMSMs with ferrite PMs, are reviewed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper describes a procedure for a practical synthesis of both a synchronous reluctance motor and a permanent magnet assisted synchronous reluctance motor. The procedure is completely analytical, yielding a rapid drawing of the motor geometry, taking into account both magnetic and mechanical considerations. From the application requirements, the external volume of the motor is computed. The further practical needs, such as maximum outer space, maximum available length, existing stator lamination, and so on are considered. Then, the design of the rotor geometry is carried out. The PM size is determined considering the demagnetisation limit according to the maximum current loading. [ABSTRACT FROM AUTHOR]

This paper presents the comparison of three-phase and five-phase permanent magnet assisted synchronous reluctance motors (PMa-SynRM) in terms of their design and performance characteristics. With higher fault tolerant capability, efficiency, and reliability, the five-phase PMa-SynRM can be a better substitute when compared with the three-phase PMa-SynRM in critical applications where safety is top priority. In this study, for a fair comparison, same design procedure using in lumped parameter modelling is followed in developing the three-phase and five-phase PMa-SynRMs. The models are optimised to minimise cost and maximise efficiency. For further detailed comparison of the three-phase and five-phase PMa-SynRMs, two-dimensional finite element analysis (FEA) is utilised. Performance characteristics such as torque pulsation, back electromotive force, flux linkage, d- and q-axis inductances versus their respective currents, cogging torque, efficiency plot, and torque-speed characteristics are intensively simulated through FEA. The optimised three-phase and five-phase PMa-SynRMs are fabricated with the same power rating (3 kW) and same volume. Experimental tests are conducted on the prototypes to validate the simulation resu lts. [ABSTRACT FROM AUTHOR]

Synchronous reluctance machines are very appealing for high speed traction motor design due to their robustness, simple structure, absence of magnets, and simple control. The absence of magnets means that synchronous reluctance (SynRel) machines are not susceptible to price variability and sustainability of rare-earth materials. Moreover, there are no concerns about demagnetisation or uncontrolled generation mode. However, the challenge of achieving a good constant power to speed ratio is dependent on the mechanical aspects of the design. Conventional SynRel designs perform poorly compared with the permanent magnet machines due to the presence of bridges and/or centre posts in absence of the magnets to help saturate these regions. In this case, the challenge of rotor mechanical retention is addressed with the help of a sleeve on the rotor to reduce the need for bridges and/or centre posts. Design optimisation including the mechanical aspects of the sleeve is presented in this study. The final design with a sleeve will be shown to be superior to a conventional design in terms of power density, rotor losses, saliency and torque ripple. [ABSTRACT FROM AUTHOR]

This paper presents a multi-physic analytical model for a permanent magnet assisted synchronous reluctance motor. The proposed model consists of: an electromagnetic model, an electrical model, a loss model, and a thermal model. The electromagnetic model is based on Maxwell's equations. Stator and rotor magnetic saturation is considered, as well as the effect of the magnetic bridges of the flux-barriers. The electrical model computes the terminal voltage and power factor. Copper loss and iron losses are also considered. The thermal model makes an estimation of the winding and magnet temperature. The goal is to compute the motor performances (average torque, voltage, power factor, efficiency etc.) for several current values and current angles. The analytical model results are compared with those from a finite element model and are subsequently validated by an experimental prototype. [ABSTRACT FROM AUTHOR]

This paper presents a current control design for switched reluctance motors (SRMs). The electric transfer characteristic of the motors is studied first. Their transfer function is shown to be expressible by a pure resistive component, which is not constant but varies depending on the motor current and speed. The current control design for SRMs follows the classical design technique used for DC machines, where the zeros of the PI controller cancel the poles of Ls+R. Because the transfer function of SRMs does not have any poles, an I controller is suitable for them. The integral gain should be adjusted in order to compensate the nonlinearity, that is, the variation in the equivalent resistor of the SRMs' transfer function. The values of the integral gain are tuned and tabulated for the motor speed and current. Simulation and experiment demonstrate that the current and speed of the SRMs present good responses without dependence on the motor speed and current. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 51–59, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20987 [ABSTRACT FROM AUTHOR]

A 3D boundary integral equation is applied to a model of a short-primary linear reluctance motor. The model is a double-sided construction where the primary member is surrounded by a set of secondary iron plates on both sides. Six kinds of different secondary geometries are calculated and their characteristics are discussed. For the confirmation of calculation results, a test machine is manufactured. Test results are compared with calculated ones. Furthermore, the static thrusts of a single-sided machine and a coreless PMLSM are measured and compared with those of the double-sided machine. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 58–65, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20390 [ABSTRACT FROM AUTHOR]

In this paper, sensorless control for synchronous reluctance motors (SynRMs) without signal injection and an inductance measurement for position estimation are proposed. In the case of SynRMs, accuracy of inductances is the most important factor in realizing precise position estimation because inductances are largely varied by a magnetic saturation phenomenon. Therefore, the inductance measurement method, which can measure appropriate inductances for position estimation, is important as well as a sensorless control method. The inductance measurement based on the observer is discussed, and the measurement method and the parameter adjustment method for improved stability of the closed loop are proposed. The proposed method can measure inductances easily and be applied for permanent magnet synchronous motors, too. Finally, the proposed sensorless control method is verified experimentally. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 70– 80, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.20274 [ABSTRACT FROM AUTHOR]

This paper presents a new characteristics analysis of a dynamic mathematical model for synchronous reluctance motors, which is recently attracting attention in conjunction with the problem of rotor phase selection and estimated based on the extended BEMF (back electromotive force) for sensorless drive. This paper gives the following new characteristic results in a simple unified analytical manner. (1) Change between positive and negative salient pole phases requires basically no modification to the dynamic mathematical model in the general reference frame. (2) Selection of positive or negative salient pole phase as rotor is no more than a preference of designers. (3) There exists a very simple method of deriving two stator flux models for explicit expression of the extended BEMF. (4) At least four circuit equations with the extended BEMF exist, which are equivalent to each other on the same reference frame. (5) There exists duality among the four circuit equations from the viewpoints of rotor phase selection. (6) The duality reinforces the above-mentioned five results. Main results of this paper correct or reinforce the results recently reported by others. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 69–75, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20244 [ABSTRACT FROM AUTHOR]

The d-axis inductance of reluctance motor is affected by not only the d-axis current but also the q-axis current, because of cross magnetic saturation between the direct and quadrature axes. This situation is similar for the q-axis inductance. The authors propose a method to determine the d-axis inductance related to the d- and q-axis currents and the q-axis inductance related to the d- and q-axis currents from a standstill test. This method involves the following four steps. First a rectangular-wave voltage, alternated between plus and minus, is applied to the two armature winding terminals after breaking the rotor in the d-axis position. Secondly, the voltage and current between the terminals are measured. Thirdly, the d-axis inductance related with d-axis current is calculated from the voltage and current. Finally, the process above is repeated when a DC current flows from the remaining armature terminal to neutral point terminal and the d-inductance related to the d- and q-axis currents is derived. A similar treatment applies when determining the q-axis inductance related to the d- and q-axis currents in the q-axis rotor position. The method is implemented on a 1.1 kW–178 V–6.3 A-4P–2200 min-1 flux barrier type reluctance motor. Results of load performance on a vector controlled reluctance motor measured by on-load tests and calculated from the d- and q-axis inductances obtained by the proposed method clearly demonstrate the validity of the proposed method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 52–59, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10377 [ABSTRACT FROM AUTHOR]

In this paper, we propose a new hybrid-type switched reluctance motor (SRM) with salient pole stator, which has a pair of permanent magnets attached symmetrically between the iron poles of the rotor. We describe experimental results not only on the basic characteristics of the hybrid SRM, but also characteristics with a current control loop under optimized advanced firing angle and cutoff angle control. Considerable improvement of machine performance, especially in the efficiency and power factor, for the hybrid SRM over the conventional VR-type SRM is confirmed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(3): 72–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10285 [ABSTRACT FROM AUTHOR]

The switched reluctance motor (SRM) exhibits desirable features including simple construction, high reliability, and low cost. However, the SRM has not been put into practical applications widely because of its large torque ripple, acoustic noise, and low power factor. Furthermore, the quantitative analysis and optimum design of the SRM have not been clarified thoroughly. In this paper, the authors propose one method for calculating the operating characteristics of the SRM based on SPICE, the general-purpose circuit simulation program. The calculated results obtained in the trial 8/6 SRM show good agreement with the experimental ones. The method is useful for optimum design of the SRM. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 50–56, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.10092 [ABSTRACT FROM AUTHOR]

High-performance drive of synchronous motors such as a permanent magnet synchronous motor and a synchronous reluctance motor can be achieved by current vector control. In such drive systems, the armature current is controlled as a sinusoidal waveform based on rotor position information from a high-resolution position sensor, and the current vector (d- and q-axis currents) is suitably controlled by current feedback control. This paper proposes a current sensorless drive system with a low-resolution position sensor in order to simplify the SM drive system. High-performance current control is achieved in the proposed drive system, where the current sensors are eliminated and the simulated currents are used for current control. The low-resolution position sensor is used instead of a conventional high-resolution position sensor, and the higher position information is estimated. The steady-state and transient characteristics are examined in several experiments with respect to the synchronous reluctance motor and the interior permanent magnet synchronous motor. It is confirmed that sinusoidal current drive, high-performance current vector control, and speed control can be achieved by the proposed drive system. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 34–43, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10072 [ABSTRACT FROM AUTHOR]

This paper reports an IPMSM rotor configuration with a concentrated-winding stator. The inductance of the concentrated winding is greater than that of the distributed winding and the flux density of the concentrated winding contains higher harmonic components. The result is higher winding losses than in the IPMSM with a distributed-winding stator. We discuss three types of interior magnetic rotor with different saliency ratios. In the lower speed range, the highest-saliency rotor is effective in decreasing the load current and copper losses. On the other hand, in the higher speed range, the higher-saliency rotors result in greater iron losses and lower motor efficiency; in this range, the lower-saliency rotor is effective in decreasing iron losses and increasing motor efficiency. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(4): 71–78, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10005 [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model of the synchronous reluctance motor in a new form is established, followed by a new analysis of stator linkage flux of the motor, which characterizes the motor and plays an essential role in developing new rotor salient-pole orientation methods for sensorless vector controls. Finally in a unified manner based on the inherent characteristics of the flux, six new potential salient-pole orientation methods are developed and proposed. © 2002 Scripta Technica, Electr Eng Jpn, 139(2): 61–71, 2002;DOI 10.1002/eej.1153 [ABSTRACT FROM AUTHOR]

A synchronous reluctance motor has many advantages because it has no permanent magnet, such as low back emf in high-speed operation, maintaining performance in a high-temperature environment, and so on. Therefore, many rotor constructions have been studied and developed. The rotor with multiflux barrier structure has the merit of easy construction and high performance. The linear synchronous reluctance motor has been developed. It is necessary to improve the performance of the mover design for industrial use, because of its low power factor. In this paper, we propose a novel configuration of mover for the linear synchronous reluctance motor, and examine the static characteristics of the motor with reluctance equalization design by means of the finite element method. From analytical results, it is demonstrated that the static characteristics of the linear synchronous reluctance motor are greatly improved by the reluctance equalization design at the iron layer in the mover. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 61–69, 2002; DOI 10.1002/eej.1139 [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous motors (PMSMs) are widely used in many applications as high-performance variable-speed drives. In traction drives, such as those used for electric vehicles or for the compressor drives of air conditioners, a wide constant-power speed range and high-efficiency operation are desired. The aim of this paper is to develop a high-performance PMSM that offers high-efficiency performance in the high-speed region, including light-load conditions, as well as a wide constant-power speed range. Simulations show that the proposed interior PMSM, which produces chiefly reluctance torque and in which the permanent magnet flux assists torque production, is capable of meeting the above performance requirements. A prototype PMSM is designed in accordance with this new design concept and several drive tests are carried out. The saliency ratio of the prototype IPMSM is about 5, and, as a result, reluctance torque is the principal torque component, representing more than 70% of total torque. The prototype IPMSM can attain a constant-power speed range of up to 5:1 with high-efficiency drive in the high-speed, constant-power region. The proposed IPMSM is suitable for variable-speed drives requiring high-speed, constant-power operation. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 60–68, 2001 [ABSTRACT FROM AUTHOR]

Compared to the conventional SRM, fully-pitched winding reluctance motors have a higher salient ratio for given motor dimensions. In addition, since the generated torque of the motor is determined as the product of the rate of change of mutual inductance with respect to a rotor position and winding current amplitude of the corresponding two phases, the motor is suitable for the bipolar current drives. Accordingly, the conventional general-purpose inverter drive of the fully-pitched winding reluctance motor is possible. In this case, the optimum lead angles of voltage play an important role in obtaining the maximum torque and maximum torque/current ratio operations. In this paper, a scheme for determining the optimum angles of voltage without any measurement, and a method for evaluating the drive characteristics in the design stage are proposed by a combination of simple magnetic and electrical analysis. The effectiveness of the proposed analytical scheme is verified by an experiment using a 400-W prototype fully-pitched winding reluctance motor. © 2000 Scripta Technica, Electr Eng Jpn 134(1): 45–52, 2001 [ABSTRACT FROM AUTHOR]

Although the reluctance motors are attractive from the standpoints of simple construction and drive electronics, the relatively high torque ripple and acoustic noise are major drawbacks. These drawbacks limit motor applications. In this paper, the torque ripple suppression of the reluctance motor under the sinusoidal current drive is examined. The analysis shows that the torque ripple is caused by the spatial harmonics of inductance. One approach is based on the compensation current generated with the spatial harmonics of inductance. Another is based on the modification of rotor tooth configuration to eliminate the spatial harmonics. According to the proposed strategies, torque ripple suppression characteristics can be evaluated at the design stage of the motor. Both approaches have been verified by experiments. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 118–128, 2000 [ABSTRACT FROM AUTHOR]

The authors have previously presented a control scheme for synchronous reluctance motors in which the motor current is controlled to keep the MMF (magnetomotive force) phase angle constant, and have shown that a simpler control scheme is possible by using an N-speed synchro for a 2N pole motor. However, conventional brushless synchros are expensive and bulky due to the intricate construction, where a rotary transformer supplies current to the exciting winding on the rotor core. The authors have therefore developed a novel VR (variable reluctance) synchro without the rotary transformer. This paper describes the theory of the novel VR synchro and presents measured waveforms of the output voltages of a prototype VR four-speed synchro. In addition, a variable speed drive system for eight-pole reluctance motors which uses the new control scheme is introduced. In this system, the VR synchro is directly connected to the motor shaft, whose output voltages are demodulated and directly used as the current phase command for the inverter current supplied to the motor. Experimental results show a satisfactory speed response for four-quadrant drive. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(3): 54–63, 1997 [ABSTRACT FROM AUTHOR]

The authors and others developed a 15 kW revolving-armature type commutatorless motor deriving high magnetic loading. The commutatorless motor was first manufactured with interpole and compensating windings having a construction allowing easy installation and removal of interpoles. It was found from this experiment that this motor was improved in overload torque and the effect of interpoles did not affect compensating windings of the spare angle improvement. Therefore, the compound commutatorless motor (with compensating windings) was manufactured as an experiment. A high output of 190% power was derived by this motor and compensating windings were not needed. By characteristics analysis and simulation, the main factor by which this high output was obtained was that the leakage reactance Xl of this motor was half that of old commutatorless motors. This paper reports this effect, including the experimental data. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 82–95, 1997 [ABSTRACT FROM AUTHOR]

A switched reluctance motor (SRM) circuit drive system caused many nonlinear effects due to convex construction. The linear control methods were hard to achieve good performance for the SRM circuit drive. The adaptive nonlinear backstepping control system using switching function is proposed for controlling the SRM drive system to obtain good performance. To reduce chattering of control effort, the adaptive nonlinear backstepping control system using adaptive law is proposed to estimate the required lumped uncertainty. When the inertia of the counterweight is varying, this proposed method cannot get a satisfactory performance. The adaptive nonlinear backstepping control system using mended recurrent Romanovski polynomials neural network with adaptive law and error‐estimated law is proposed for controlling the SRM drive system to raise robustness of the SRM drive system. Furthermore, two variable learning rates in the mended recurrent Romanovski polynomials neural network are adopted by using mended particle swarm optimization (PSO) algorithm to speed up parameter's convergence. Finally, comparative performances through some experimental results are verified that the proposed control system has better control performances than those of the proposed methods for the SRM drive system. [ABSTRACT FROM AUTHOR]