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In a common dc-link dual-fed open-end winding permanent magnet synchronous motor (OEW-PMSM) topology, it is well known how the additional flow of a zero-sequence current (ZSC) is permitted. The low zero-sequence impedance characteristic of high-speed machines leads to high-intensity and high-frequency ripple of the ZSC. Therefore, there is a necessity to eliminate the zero-sequence-voltage (ZSV) produced by the two voltage source converters that feed the machine. Furthermore, the non-sinusoidal back electromagnetic force (back EMF) causes the circulation of a third harmonic ZSC. An OEW-PMSM high-speed starter-generator fed by a dual-inverter with a single dc-link is considered. Part I of this paper proposes a modulation for the considered topology able to eliminate instantaneously the ZSV produced. In this paper, a detailed analysis of the deadtime (DT) effect on the ZSV has been carried out and a novel hysteresis control for the ZSC using the DT as a control action is presented. The DT produces a ZSV distortion on the zero-axis that can be used to control the third harmonic ZSC flowing due to the non-sinusoidal machine back EMF. [ABSTRACT FROM AUTHOR]

This paper focuses on the electromagnetic vibration and its reduction in PM brush dc motors. First, the air gap flux density distribution and the radial force density distribution are derived in detail, and compared with the results of the finite element method. Next, two types of vibration sources, called pulsating force and bending moment, are analyzed. Then, two passive improvement methods, called varied PM pole width in axial direction and copper ring, are proposed to reduce the magnetic forces and their vibration, and their principles of the vibration reduction are described in detail. For further explanation, a rotor-skewed motor is used for comparison, and the radial force on the motor is discussed and the influence of four different thicknesses of copper ring on the motor vibration is analyzed. Finally, three 2p/24s sample motors are manufactured and the experimental vibration results confirm the analysis and the proposed improvement technique. [ABSTRACT FROM AUTHOR]

This paper presents the design and performance details of the Chevrolet Volt electric propulsion system. The propulsion system has two machines: One machine is operating mostly as a motor while the other machine is operating mostly as a generator. Both machines of the Volt electric drive system are permanent-magnet ac synchronous machine types with the magnets buried inside the rotor. The motor has distributed windings. However, as opposed to a conventional stranded winding, the Chevrolet Volt motor has bar-wound construction to improve the motor performance, particularly in the low to medium speed range. At higher speed, the skin and proximity effects in the stator bars lead to increased stator winding losses but are addressed in the design. The bar-wound construction also has excellent thermal performance, in both the steady-state and transient conditions, necessary for full electric vehicle (EV) driving. The generator uses concentrated windings. The concentrated winding construction has good slot fill and short end-turn length. These features resulted in good performance in the intended operational region and were an enabler for machine packaging inside the transmission. Both the machines exhibit excellent efficiency and exceptionally smooth and quiet operation. The machine design and construction details, as well as the measured thermal, electromagnetic, and acoustic noise performances, are presented in this paper. [ABSTRACT FROM AUTHOR]

Pitch systems are one of the components with the most frequent failure in wind turbines. This paper presents a two-stage fault detection and classification scheme for electric motor drives in wind turbine pitch systems. The presented approach is suitable for application in offshore wind farms with electric pitch systems driven by induction motors as well as permanent magnet synchronous motors. The adopted strategy utilizes three-phase motor current sensing at the pitch drives for fault detection and only when a fault condition is detected at this stage, features extracted from the current signals are transmitted to a support vector machine classifier located centrally to the wind farm. The proposed method is validated in an in-house setup of the pitch drive. [ABSTRACT FROM AUTHOR]

Integrated battery charging (IBC)—multiplexing the motor windings as line inductors for charging electric vehicle battery packs—can improve the onboard charging capability without increasing the weight and cost. However, during the charging operation, currents flowing in the stator winding definitely generate a magnetic field, which may demagnetize the permanent magnets (PMs) in the PM traction motors. In this paper, the demagnetization effects of IBC current on magnets in interior PM machines are compressively investigated. In this paper, a recursive algorithm to update the PM magnetization states by using a parallelogram hysteresis model at different demagnetization levels is applied. The PM temperature is also considered for establishing this model. By coupling this algorithm to the finite element analysis, the demagnetization transit at different demagnetization levels can be assessed. By decomposing the flux density of each node within the magnets along its magnetization direction, irreversible demagnetization can be accurately evaluated. Impacts from both the pulsating and rotating demagnetization magnetic fields during the IBC operation are assessed and compared. [ABSTRACT FROM AUTHOR]

Fractional-slot concentrated-winding (FSCW) interior permanent magnet synchronous motors (IPMSMs) have been attracting considerable attention due to their high power density, high efficiency, short end winding, high slot fill factor, low cogging torque, excellent flux-weakening, and fault tolerance capability. However, compared to integral-slot distributed-winding (ISDW) IPMSMs, the key challenge of using FSCW configurations is the significant rotor losses, particularly at high speed. To figure out the IPMSM with which winding configuration is more suitable for electric vehicle (EV) application, the thermal behaviors of four IPMSMs with ISDW, single-, double-, and four-layer FSCWs are comprehensively and comparatively investigated in this paper. First, electromagnetic design and loss analysis of the four IPMSMs are investigated to meet the EV traction motor requirements. Second, finite-element method is employed to investigate the thermal performance of the IPMSMs under different rotational speeds and torque overload capacities. Thirdly, experiments implemented on an ISDW prototype are carried out to validate the presented analysis method. Finally, some conclusions are drawn for a suitable winding configuration selection and the PM traction motor design. [ABSTRACT FROM AUTHOR]

This paper provides a theoretical and experimental discussion on a modular multilevel triple-star bridge-cell converter with focus on mitigating the capacitor-voltage fluctuation contained in each bridge cell. A new control method proposed in this paper is characterized by properly superimposing both common-mode voltage and circulating currents in the whole speed range. Moreover, this paper optimizes the amplitude and frequency of the superimposed common-mode voltage on the basis of theoretical analysis, thus resulting in minimizing the voltage fluctuation. The optimized control method makes both voltage fluctuation and cluster-current amplitude smaller than do the existing methods. Experimental waveforms obtained from a three-phase downscaled system using a 370-V, 15-kW, 75-Hz, six-pole, permanent-magnet synchronous motor verify good start-up performance from a standstill to the rated speed, keeping both capacitor-voltage and cluster current within acceptable levels. [ABSTRACT FROM AUTHOR]

This paper investigates a method to increase fuel economy of motors for an electric vehicle (EV) traction system. The low-torque region of an EV motor is frequently used in everyday urban driving and in fuel economy measurement. Pulsewidth modulation (PWM) carrier harmonic iron loss accounts for a high percentage of total loss for EV motors in this region. This paper reveals the relationship between phase current and carrier harmonic iron loss for a permanent-magnet synchronous motor (PMSM) in the low-torque region. Thus, a novel carrier harmonic loss reduction technique is proposed and applied to two sets of three-phase windings for a concentrated winding PMSM. The loss is successfully reduced in a 70-kW EV motor as well as a two-dimensional finite-element method (2-D-FEM) calculation. The efficiency of the developed motor is calculated and compared with that of a conventional motor in the JC08 mode driving cycle. [ABSTRACT FROM PUBLISHER]

This paper deals with the design and testing of an interior permanent-magnet (IPM) machine that exhibits advanced features. It adopts fractional-slot (FS) nonoverlapped coil windings that reduces the end winding length, i.e., the Joule losses and machine cost. As a consequence, higher rated current can be supplied so that higher torque density and higher efficiency in a wide operating region can be reached. The rotor saliency increases the performance in flux-weakening operating region and the fault-tolerance capability. In order to decrease the torque ripple, it is important to minimize the interaction between the magnetomotive force (MMF) harmonics due to the stator currents and the rotor anisotropy. To do that, the winding has been optimized so as to minimize the MMF harmonics, taking advantage from the higher degree of freedom of the four-layer winding. However, the so-called slot-harmonics cannot be minimized by rearranging the winding coils. Hence, the rotor geometry has been designed so as to minimize the impact of such slot-harmonics. A 12-slot 10-pole IPM FS machine has been designed and manufactured. The experimental tests confirm the expectations. [ABSTRACT FROM AUTHOR]

This paper reviews recent developments in power loss analysis applicable, but not limited to, the thermal design of permanent-magnet machines. Accurate and computationally efficient loss prediction is an essential element in the thermal analysis of electrical machines and has become an increasingly important part of the machine design process. The continuous drive toward “more electric” technologies has resulted in a need for a more comprehensive and detailed design approach, where various multiphysics and multidisciplinary effects are accounted for. This “design for application” methodology relies strongly on the advancements and evolution of the existing theoretical and experimental design techniques to satisfy the evermore-demanding machine design requirements. The thermal behavior and efficiency of the power conversion are essential performance measures in the “design for application” approach. An overview of the challenges and limitations regarding power loss analysis in the context of the thermal design of electrical machines is provided in this paper. All of the major loss components associated with the active parts of a machine assembly are discussed. [ABSTRACT FROM AUTHOR]

Rotor magnet condition is important to maintain a stable permanent magnet synchronous motor (PMSM) operation. In this paper, Vold–Kalman filtering order tracking (VKF-OT) and dynamic Bayesian network (DBN) are employed for the real-time rotor demagnetization detection from the torque ripple. First, a torque ripple model of the PMSM considering electromagnetic noise is proposed, and the torque variation is studied to determine the effect of the demagnetization on the torque ripple, which indicates that it is feasible to detect the magnet demagnetization by analyzing the torque ripple. Then the torque is processed by wavelet transform to eliminate the electromagnetic disturbances. Second, the VKF-OT is introduced to track the order of the torque ripple of the PMSM to extract the torque ripple characteristics as the feature reflecting changes in magnet status. Third, the feature is employed to train the DBN for the rotor magnet demagnetization detection and prediction during motor operation. The proposed approach is a noninvasive and an online method that can be embedded in the physical motor controller. The validation results demonstrate that this method can detect the uniform demagnetization over a wide motor speed range. [ABSTRACT FROM AUTHOR]

In this paper, a dual-fed (DF) common dc-link topology open-end winding permanent magnet synchronous motor for aircraft high-speed starter–generator application is considered. While on one hand the common dc bus configuration significantly simplifies and reduces the costs of the topology, on the other hand it allows the zero-sequence current (ZSC) to flow freely in the system. High-speed machines are characterized by low phase inductance, which implies low zero-sequence impedance. A small time constant of the zero-sequence circuit produces a high-frequency, high-intensity ZSC ripple with the risk of harming the switching devices. This paper presents a novel hybrid space vector pulsewidth modulation that allows to instantaneously eliminate the zero-sequence voltage (ZSV) produced by the two voltage source converters (VSCs) by square wave modulating one of the two VSCs. The non-sinusoidal machine back electromotive force (EMF) has been considered and the effect of the converters’ dead time on the ZSV has been analyzed. The square-wave-modulated VSC uses insulated-gate bipolar transistor (IGBT) devices, whereas the other uses Silicon Carbide (SiC) technology. The proposed topology is tested through both simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper proposes an optimized design of permanent magnet (PM) synchronous motor (PMSM) using hybrid-type PM for improving the output characteristics and reliability. Here, the hybrid-type PM is defined as using both neodymium PM (Nd-PM) and ferrite PM (Fe-PM) in a rotor. First, a basic design of PMSM is conducted by considering the magnetic equivalent circuit and applying the magnetic characteristic of Fe-PM changed by the reversed flux of Nd-PM. For optimizing the motor using hybrid-type PM, parallel configuration of reluctance factors is helpful for increasing the output characteristics, and it is analyzed by using a finite element method (FEM). In addition, by using an algorithm, an optimized design is suggested for obtaining maximum torque. The performances of target and proposed motors are compared through FEM. Next, the irreversible demagnetization of each motor is analyzed at high and low temperature, and the demagnetization phenomenon of two-type motors is compared for verifying the reliability of the proposed motor. Finally, prototypes of reference and proposed models are developed for evaluating the enhanced performance through comparison between the two motors. [ABSTRACT FROM AUTHOR]

This paper investigates the rotor cavity positioning and the combination of stator slot and rotor effective slot number on the eddy-current loss for interior permanent-magnet/reluctance machines operating under deep field-weakening conditions. A new closed-form expression for the stator and rotor eddy-current loss is developed. The optimal barrier-positioning for the minimum total loss and the effect on the eddy-current loss of varying the stator slot and rotor effective slot number are investigated for one-, two-, three-, and full-layered rotors. [ABSTRACT FROM PUBLISHER]

This paper describes a $d$– $q$-axis model of synchronous permanent-magnet machines at high frequency. Both the inductive and resistive saliencies are taken into account, and the model is suitable for investigating the self-sensing capability of the machines. It is proved that the high-frequency machine response can be described by means of three complex parameters, which form a symmetrical matrix. It is also shown that the high-frequency resistances between the $d$- and $q$-axes exist, and they may assume a negative value. Experimental results are included in this paper to prove the developed theory. [ABSTRACT FROM PUBLISHER]

In this paper, the ringed-pole surface-mounted permanent-magnet machine is investigated from the point of view of the ring losses. The rings around the poles create a high-frequency anisotropy that is useful to detect the rotor position by means of a high-frequency signal injection. However, the presence of the rings causes additional rotor losses. The causes of ring losses are investigated in the paper. The first cause is the high-frequency signal injection itself. The harmonics in the airgap magnetomotive force, which are not synchronous with the rotor and hence induce currents in the rings, are the second source of losses. The third source is the airgap flux fluctuation due to stator slotting. Machines of different sizes and winding types are investigated. A finite-element analysis and an analytical model are used to estimate the ring losses, comparing the results. The influence of the ring cross-sectional area on the ring losses is analyzed, showing that the ring losses can be reduced in certain configurations. [ABSTRACT FROM PUBLISHER]

The next big change in various industry applications is associated with power dense motors, such as permanent magnet synchronous motors (PMSMs). Utilization of multiphase PMSM can offer an additional fault-tolerant capability to their applications. Combining both advantages, this paper proposes a simple yet robust current control strategy for a five-phase PMSM under normal operation and in a case of a loss of one phase. Traditional linear current controllers successfully applied to reference tracking of a healthy motor may become less efficient during postfault operation due to additional unmodeled dynamics. This paper proposes a modified angular transformation to a special rotating frame in which the postfault permanent magnet flux linkage remains unchanged and the motor model remains decoupled. Following this, a nonlinear current control scheme based on sliding mode control is proposed, which successfully treats model inaccuracies and provides good dynamic performance and tracking accuracy. Feasibility of the proposed control strategy is experimentally validated on a laboratory scale PMSM motor with a digital signal processor/field programmable gate array based drive. [ABSTRACT FROM AUTHOR]

This paper presents a novel axial vibration suppression method in two-axis actively positioned permanent magnet bearingless motors. Only radial directions are actively positioned. The axial and tilting directions are passively stabilized by the magnetic attraction force between the stator core and the rotor permanent magnet. Generally, a damping force is considerably low in the axial and tilting directions. Therefore, when an axial disturbance force is applied to the rotor, the axial vibration is generated, and then, the vibration cannot be suppressed at a critical speed. In this paper, a novel axial vibration suppression method by d-axis current is proposed. The damping force is generated by d-axis current regulation. In this proposed method, the rotor axial position is estimated from the flux linkage variation in the motor winding. Therefore, an additional displacement sensor is not necessary. In experiments, it is confirmed that the rotor axial vibration is successfully suppressed by the proposed method. [ABSTRACT FROM AUTHOR]

There is significant interest in the development of switched reluctance machines (SRMs) for use in automotive traction applications. This has been driven by their low cost compared with rare earth permanent-magnet-based motors, driven by the high cost of rare earth permanent magnets, coupled with their potential for competitive torque densities. This paper describes the development of a variant of the SRM, utilizing a segmental rotor construction, which has previously been demonstrated to provide the potential for significant improvement in torque densities compared with SRMs with a conventional toothed rotor construction. This paper describes a strategy that has been developed to optimize the Segmental Rotor SRM to maximize efficiency with the aim of achieving performance equivalent to that of the 80-kW interior permanent-magnet machine utilized in Nissan's LEAF electric vehicle. Optimization applies a combination of static and dynamic analyses in order to achieve a full and computationally efficient assessment of motor performance across different regions of the torque speed envelope. Test results from a prototype motor are also presented. [ABSTRACT FROM PUBLISHER]

Interior permanent magnet (PM) machines are considered the state of the art for traction motors, particularly in light-duty hybrid and electrical vehicles. These motors usually use neodymium–iron–boron (NdFeB) PMs. These magnets include both light rare-earth materials such as neodymium (Nd) as well as heavy rare-earth materials such as dysprosium (Dy). The main purpose of Dy is to enhance the magnet coercivity to avoid demagnetization under both high temperatures as well as flux weakening. One of the key risks in terms of using these rare-earth magnets is the significant fluctuation/increase in their prices over the past few years. Applications that use large quantities of these magnets, such as traction motors and wind generators, are the most affected by these fluctuations. There has been an ongoing global effort to try to reduce or eliminate the use of rare-earth materials (particularly Dy which is the most expensive) without sacrificing too much performance. This paper will focus on advanced spoke designs targeting traction applications. The goal of this paper is to come up with new spoke designs using various grades of Dy-free magnets as well as ferrites targeting the same set of specifications. This paper will provide a detailed comparison between the various designs highlighting the key tradeoffs in terms of power density, efficiency, flux-weakening capability, and magnet susceptibility to demagnetization. Also, a prototype using ferrites has been built and tested, and the experimental results will be presented. [ABSTRACT FROM AUTHOR]

The so-called integrated starter–alternator (ISA) is a high-efficiency electrical machine that is connected to an internal combustion engine obtaining mild hybrid electric vehicles. The ISA has a twofold task: starting up the engine and generating electrical energy to be stored into a battery. This paper is focused on the first task. Two different motors are investigated: an external rotor surface permanent magnet (SPM) machine and an interior permanent magnet (IPM) machine. For drive control, both motors require knowledge of their rotor position; then, a sensorless technique based on the high-frequency (HF) voltage injection for rotor position detection has been implemented. In order to create an HF anisotropy in the SPM rotor configuration, a ringed-pole solution has been adopted. Experimental tests have highlighted that the first machine has a clear capability of starting up the engine with good speed and position estimation in spite of the particular nonconstant load torque. As regard the IPM machine, the sensorless engine startup appears not possible because the anisotropy disappears at a high current level due to saturation effects. [ABSTRACT FROM PUBLISHER]

There are characteristics of permanent magnet (PM) motors, both by design and by application, that create new challenges in certifying for oil and gas environments. To date, certifications of PM motors are being handled on a case-by-case basis. This paper will identify areas in the standards that require additional clarification or assumptions when applying PM motors. [ABSTRACT FROM AUTHOR]

Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis, and testing of an advanced interior permanent magnet (PM) machine that was developed to meet the FreedomCAR 2020 specifications. The 12-slot/10-pole machine has segmented stator structure equipped with fractional-slot nonoverlapping concentrated windings. The rotor has a novel spoke structure/assembly. Several prototypes with different thermal management schemes have been built and tested. This paper will cover the test results for all these prototypes and highlight the tradeoffs between the various schemes. Due to the high machine frequency ( $\sim$1.2 kHz at the top speed), detailed analysis of various loss components and ways to reduce them will be presented. In addition, due to the high coolant inlet temperature and the fact that the machine is designed to continuously operate at 180 ^\circ\C, detailed PM demagnetization analysis will be presented. The key novelty in this paper is the advanced rotor structure and the thermal management schemes. [ABSTRACT FROM AUTHOR]

This paper investigates how the orientation of the applied demagnetizing magnetomotive force (MMF) affects the demagnetization behavior of Nd-Fe-B magnets that are widely used for permanent-magnet synchronous machines (PMSMs). This paper designs and builds a customized test fixture that can produce a magnetic field with varying orientation and intensity to demagnetize magnet samples. A computer-controlled 2-D mapping device is used to record the flux density above the test samples. The measurement results are compared with the 3-D finite-element analysis simulations. The understanding and insights obtained from this paper will be used to improve the robustness of magnet design for high power density PMSMs with improved capability of withstanding demagnetization during overcurrent faults. [ABSTRACT FROM AUTHOR]

This paper proposes a novel detached winding configuration for asymmetric six-phase double-stator axial flux permanent magnet machines aiming at fault-tolerant applications. Due to the machine unique double-stator structure, the six-phase winding can be separated into two three-phase windings with 30 electrical degree angle shift and arranged in different stators, which is the basic idea of the detached winding. In this paper, the connection of detached six-phase winding is first given, followed by a comprehensive comparison of the conventional six-phase winding and the detached winding in aspect such as the winding factor, electromotive force, inductances, rotor eddy current loss, and torque in normal condition. Performance under fault-tolerant operation is investigated by the copper loss minimization control strategy. The results show that by applying the detached winding instead of the conventional winding, rotor eddy current losses could be reduced by 25% and 70% under normal and fault-tolerant operation, respectively, without sacrificing torque output. This implies that under fault operation, the excess heating in rotor could be reduced and the machine durability can be enhanced. A prototype machine is built to validate the performance of the detached winding design. The experimental results match well with simulation analysis. [ABSTRACT FROM AUTHOR]

A modified-virtual-space-vector-based dc-link voltage balancing strategy is proposed in this paper for a three-level inverter. In the proposed strategy, the summation of the three-phase currents for virtual vector needs not to be zero and it also keeps the two capacitor voltages balanced with wider range of load variations. The duty cycles for all the power switches are also derived in this paper using a nearest three-voltage vector scheme. Due to the reduced use of the medium voltage vectors, the proposed control strategy can considerably decrease the neutral-point voltage fluctuation for lower power-factor-based loads as well. Detailed simulation and experimental studies are also carried out to show the effectiveness of the proposed system with a dc-link voltage balancing strategy with permanent magnet synchronous machine. Voltage and current harmonic distortions are also presented with change in modulation index. A Dspace-based real-time operating system is used for real-time implementation with a 6.0-kW surface permanent magnet synchronous motor. [ABSTRACT FROM PUBLISHER]

One of the major topics of switched reluctance machines (SRMs) is how to reduce the acoustic noise and vibration without decreasing the efficiency. In this paper, a few novel current profiling methods are proposed to reduce the acoustic noise by flatting the radial force sum and to reduce optimal torque ripple with best efforts to enhance the efficiency. The proposed method is adopted to the 18/12 pole SRM, which has identical outer dimensions and competitive torque, output power, efficiency, and operating region of the permanent-magnet motor used in the hybrid vehicles. It is found that the proposed method can improve not only the radial force ripple characteristic but also the iron loss minimization. The efficiency enhancement is also found to be possible in a few cases depending on the demanding criteria; thanks to the phase shift of the fundamental component of the current waveform. The proposed method is verified in the experiments. [ABSTRACT FROM AUTHOR]

This paper presents a novel rotor design for interior permanent-magnet machines. The advantage of this solution is the near elimination of magnetic flux leakage in the rotor iron bridges, which represents the main disadvantage of this machine topology. Therefore, enhanced magnet utilization results from the new rotor arrangement. This concept is accomplished by utilizing non-magnetic wedges to lock the magnet in a robust rotor structure. This paper is supported by both electromagnetic and mechanical finite-element method analyses. Significant results of this investigation are presented and discussed in this paper. A machine prototype with the implemented innovative rotor design was manufactured and tested for the validation of the finite-element simulations. Several manufacturing methods of the wedge have been investigated in order to evaluate the resultant wedge characteristics and in order to assess the feasibility of mass production. The total cost analysis yields potential machine cost reduction. [ABSTRACT FROM PUBLISHER]

The flux-intensified interior permanent-magnet synchronous machine (IPMSM) (FI-IPMSM) lends itself to designing for good self-sensing properties. This paper begins by evaluating the self-sensing position estimation performance of a suitably designed FI-IPMSM machine using different high-frequency injection methods. This paper then uses an alternative square-wave injection method to estimate the FI-IPMSM rotor position. The experiment results show that the estimation accuracy and system robustness are improved. It is known that secondary saliencies and saliency offset caused by the saturation of the machine can degrade the estimation accuracy. This paper also includes modeling, measurement, and decoupling methods that mitigate these undesirable effects, which are also implemented using an experimental FI-IPMSM. Estimation accuracy and torque ripple caused by the injection current are examined for this FI-IPMSM. Comparisons of the methods are presented. [ABSTRACT FROM AUTHOR]

In this paper, an overview of the main motor features influencing the protection devices settings is presented, pointing out key differences between three-phase direct-on-line (DOL) motors of different efficiency classes. The results of experimental tests and simulations are presented and discussed in the scope of the motor protection against overload, short-circuit, current unbalance, and locked-rotor conditions, for 7.5-kW, four-pole, IE2- and IE3-class squirrel-cage induction motors (SCIMs) and for IE4-class line-start permanent-magnet motors (LSPMs), offering important data related to their electrical and thermal behaviors. Two commercial digital thermal-magnetic motor protection devices, whose thermal models were designed for IE1- and IE2-class motors, are evaluated in terms of operation effectiveness in the tested motors. This paper is important for industry due to the significant penetration of IE3-class induction motors, as well as to the recent introduction into the market of IE4-class induction motors and LSPMs. [ABSTRACT FROM PUBLISHER]

This paper describes a systematic method for optimally designing with multiple objectives and differential evolution (DE) algorithms, current regulated electronically controlled synchronous reluctance (SynRel) machines. A large-scale study with thousands of designs calculated with a ultrafast computationally efficient electromagnetic finite-element analysis (CE-FEA) establishes the performance limitations of conventional radially laminated technology with multiple flux barriers. The potential advantages of employing permanent-magnet (PM)-assisted technology with additional ferrites in the rotor are quantified in terms of substantially improved power factor, specific power, and efficiency. Numerical and experimental results for a 10-hp, 1800-r/min typical rating are included. [ABSTRACT FROM PUBLISHER]

A hysteresis interior permanent-magnet (IPM) motor is a solid-rotor self-starting synchronous motor. Its rotor has a hysteresis ring made of composite material with high degree of hysteresis energy per unit volume. The Neodymium Boron Iron (Nd-B-Fe) magnets are buried inside the hysteresis ring. This paper presents the analytical modeling of a hysteresis IPM motor to investigate its starting and synchronization capability for different loading conditions. A V/F controller has been designed to operate the motor at variable speeds. Simulations have been carried out to obtain the run-up responses of a three-phase four-pole 208 V, 2.5 kW hysteresis IPM motor. Simulation results are presented and analyzed in this paper. Experimental investigations have been carried out for the same 2.5-kW motor. Both the simulation and experimental results are presented in this paper. [ABSTRACT FROM AUTHOR]

Multilevel power electronic topologies are being proposed in the recent technical literature for use in power generating units, especially when the reduction in the power filter overall dimensions and the lowering of current and voltage waveform ripple and total harmonic distortion are considered of primary importance. This is the case of high-speed gen-set units, where recent design techniques on high rotational speed permanent-magnet synchronous generators (PMSGs) have significantly reduced the inductance even for industrial voltage rated applications. This paper deals with a five-level unidirectional T-rectifier (5L T-RECT); the proposed topology is theoretically investigated, and simulation results and losses analysis are achieved with reference to an insulated-gate bipolar transistor (IGBT) phase-leg module which has been manufactured on purpose and tested. [ABSTRACT FROM AUTHOR]

In this paper, two designs of interior permanent-magnet synchronous machine (IPMSM) for sensorless drive with absolute rotor position estimation capability are proposed. A conventional IPMSM design proposed for the same purpose had a demerit that for the absolute position estimation, the rotor should initially stroke for 100 degrees in the worst case. Using the proposed IPMSMs featuring asymmetric winding and asymmetric rotor geometry, the initial stroke of the rotor can be reduced to 30 degrees. Moreover, basic characteristics of the motor such as torque ripples and harmonics of electromotive force (EMF) are conspicuously improved. The proposed designs are evaluated by rigorous finite-element analyses and experimental tests. An analytical model of the proposed motors considering their asymmetric structures is also developed and provided in this paper. [ABSTRACT FROM AUTHOR]

Practical implementations of the power electronics required to operate bearingless machines with the so-called “dual-purpose no-voltage” (DPNV) windings are proposed. These windings enable a bearingless machine to use the same coils to produce both radial suspension forces and torque, which has been shown in the literature to enable better machine performance. In this paper, the use of two-level inverters is investigated for the two configurations of DPNV windings: the “parallel” and “bridge” configurations. The investigation is valid for conventional $p \pm 1$ pole-pair bearingless motors (i.e., bearingless permanent magnet and induction motors) and $p=1$ bearingless motors (bearingless ac homopolar and consequent-pole motors). The advantages and disadvantages of each configuration are explored in terms of control complexity and required hardware, potential paths for circulating currents are identified along with mitigation strategies, and experimental results are presented to validate the proposed power electronic implementation. [ABSTRACT FROM AUTHOR]

We present a method for reducing vibration in a one-axis actively positioned single-drive bearingless motor with repulsive passive magnetic bearings. The single-drive bearingless motor has only one set of three-phase windings. It generates both torque and axial suspension force, regulating the $q$- and $d$-axis currents, respectively, driven by only one three-phase inverter. Single-drive bearingless motors have the advantage of low cost. Only the axial $z$-axis is actively positioned. The radial and tilting directions are passively stabilized. Therefore, passive axis vibrations are one of the few serious problems. In this paper, we show that radial vibration originates in axial vibration. In particular, the second-order harmonic vibration with respect to rotational speed is a factor. In theoretical calculations, we derive the relationship between axial and radial vibrations. Additionally, vibration reduction methods are proposed. Finally, experiments confirm that radial vibration is reduced by 59%. [ABSTRACT FROM AUTHOR]

This paper deals with the torque production capabilities of fractional-slot permanent-magnet synchronous machines (FSPMSMs) under open-circuit faulty conditions. The developed approach considers a class of FSPMSMs where an armature is inserted in double-layer slots and is arranged by connecting in parallel the coils or suitable combinations of coils of each phase. In light of this, the machine operates at a low-voltage level. Accordingly, its integration within 42-V-technology-based automotive systems becomes much more realistic. Moreover, the adopted approach leads to a significant improvement in the fault tolerance capability under an open-circuit faulty operation. Indeed, a failure affecting a coil would discard one branch among the parallel branches of the corresponding phase, rather than affecting the total phase in FSPMSMs with series-connected coils in the armature. The approach is initiated by an identification allied to a characterization of the slot/pole combinations enabling the parallel connection of the FSPMSM phase coils or group of coils. Then, this paper considers the selected three-phase and five-phase FSPMSMs. Following an assessment of their healthy operation, the torque values developed by both machines are predicted using a 2-D finite-element analysis under different open-circuit faulty scenarios. Then, a simple control strategy based on the readjustment of the reference sinusoidal current initial phases is proposed to recover the torque production capability of both machines under a branch open-circuit fault. [ABSTRACT FROM PUBLISHER]

In the coming years, the electrification and the deployment of the electric motors in the urban transports will become a more and more widespread reality. The optimization stage of the electric motors usually does not consider in detail the real driving conditions of the car in which the motor is installed. It follows that the actual motor performance in operating points, particularly as regards the torque ripple and the efficiency, might be worse than expected. A robust solution is a required target. This paper deals with the design and optimization of a high-speed permanent-magnet-assisted synchronous reluctance motor for traction applications, taking into account both city and highway driving cycles. A procedure is employed in order to evaluate the most representative operating points, which have to be considered when a global optimization is required. An analysis of the solution robustness has been performed. Both results and advantages of the adopted methodology are highlighted. [ABSTRACT FROM PUBLISHER]

Although relatively small in size and power output, automotive accessory motors play a vital role in improving such critical vehicle characteristics as drivability, comfort, and, most importantly, fuel economy. This paper describes a design method and experimental verification of a novel technique for torque ripple reduction in stator claw-pole permanent-magnet (PM) machines, which are a promising technology prospect for automotive accessory motors. [ABSTRACT FROM PUBLISHER]

This paper presents a semicircular tubular linear machine model, which is called a circular shaft motor (CSM), with trapezoidal magnets. For a conventional CSM system, the stator is difficult to construct as designed, and the thrust characteristics are not high enough. The proposed CSM model includes trapezoidal magnets that are magnetized in the axial direction. This structure can facilitate the construction of the stator and decrease the thrust ripple. In addition, the magnetic flux characteristics are shown as new results of a CSM. Magnetic field is related to thrust characteristics closely. By investigating magnetic distribution characteristics, it is shown that the proposed model can improve magnetic field characteristics. In this paper, the structure of the proposed CSM model is described. The improvement in the thrust characteristics is verified by magnetic field analysis. The thrust characteristics of the proposed CSM system are verified in a thrust characteristics test. The magnetic flux characteristics of the proposed CSM system are compared with those of a conventional CSM system to evaluate the thrust characteristics. [ABSTRACT FROM PUBLISHER]

In the context of more electric aircraft, the use of electric actuators instead of hydraulic ones is one of the main topics of research and development in electrical engineering. A high level of reliability, the redundancy, and the compactness are required for aircraft electrical actuators. For achieving these purposes, a classical solution consists in using two identical actuators motorized by one permanent magnet (PM) motor supplied by a voltage source inverter (VSI). In this paper, a solution based on the use of only one fault-tolerant actuator performed by a two-star connected-winding (two-channel) PM motor supplied by two pulsewidth modulated VSIs is proposed. The design of the PM motor can be achieved in two different ways, which are proposed and studied in this paper. The authors focus this paper on the comparison between the two winding architectures and compare the two motors in terms of the short-circuit current and magnetic decoupling of the two windings. Both simulation and experimental results are given and discussed. [ABSTRACT FROM AUTHOR]

This paper describes the design process of a 10 kW 19 000 r/min high power density surface mounted permanent magnet synchronous machine for a directly coupled pump application. In order to meet the required specifications, a compact machine with cooling channels inside the slots and flooded airgap has been designed through finite element (FE) optimization. For high power density, high-speed machines, an accurate evaluation of the power losses, and the electromechanical performance is always extremely challenging. In this case, the completely flooded application adds to the general complexity. Therefore, this paper deals with a detailed losses analysis (copper, core, eddy current, and mechanical losses) considering several operating conditions. The experimental measurements of ac copper losses, as well as the material properties (BH curve and specific core losses) including the manufacturing process effect on the stator core, are presented. Accurate 3-D FE models and computational fluid dynamics analysis have been used to determine the eddy current losses in the rotor and windage losses, respectively. Based on these detailed analysis, the no-load and full-load performance are evaluated. The experimental results on the manufactured prototype are finally presented to validate the machine design. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of ripple current of a multimegawatt drive system fed by a pulse-width modulation (PWM) inverter are investigated. Based on the investigation, a novel PWM scheme is devised to reduce the switching loss of the inverter under an identical amount of torque ripple of a motor. The proposed PWM is composed of two parts. The first is minimum torque ripple PWM (MTRPWM), which is optimized in terms of the minimum torque ripple in high modulation index (MI). The second determines the minimum switching frequency while holding the average torque ripple less than the allowable value under various operating conditions. It is termed reduced switching frequency PWM (RSFPWM). Consequently, by simply changing the PWM method from conventional fixed switching frequency continuous PWM to the proposed PWM, MTRPWM and RSFPWM, simulation results show that the switching loss of the inverter driving a 3.5 MW induction motor is reduced to 51.6% while keeping the torque ripple in the allowable boundary, where MI is 1.12. This approach is applied to small-scale experimental sets consisting of an interior permanent magnet synchronous machine (IPMSM) motor-generator set, and an induction machine MG set in an effort to verify the validity and feasibility of the proposed method. Based on these experimental results, the cost indexes of the IPMSM and the induction machine, as defined in this paper, decrease by up to 66% and 77%, respectively, when the proposed method is applied when MI is 1.12 compared with the outcome with the conventional PWM. [ABSTRACT FROM AUTHOR]

Microstepping drive for a stepper motor is a well-known technique to improve the stepper motor performance. Normally, microstepping is carried at fixed pulse width planned. However, this method is suitable only when motors are driven at fixed predefined speeds for non-real-time applications. The problem discussed in this paper considers an application where motors need to track a given reference position profile precisely in real time, whose speed is varying at every interval of time. In such a scenario, fixed speed microstep drive does not meet the high pointing requirements and leads to poor system performance. For such applications, an innovative frequency modulation (FM) based microstep drive algorithm is developed that meets the high degree of motor pointing even at higher output angular rates. As per this scheme, pulse width and the number of steps that motor is supposed to move are derived from the reference position itself in a given amount of time, and the motor is actuated with a corresponding number of steps in real time. FM-based microstep drive is implemented with pulse-width modulation based chopper current controller in an optimized way without compromising on the motor torque margins. Transient error plots obtained through experiments clearly show the advantages of FM-based microstepping over fixed rate. This paper presents the design, analysis, simulation, and experimental results of FM-based microstep drive. [ABSTRACT FROM AUTHOR]

This paper investigates the postfault operation of a novel six-phase double-stator axial-flux permanent-magnet machine with detached winding connection. In previous research, this configuration was found to be superior to existing winding connection except that its unbalanced magnetic force in the postfault operation cannot be ignored. In this paper, an axial magnetic force balancing method (AMFBM) is proposed to reduce unbalanced magnetic force by deducing a set of special winding current. By comparing electromagnetic torque and axial magnetic force of the traditional winding current and the proposed method in postfault operations through a finite-element analysis, it is verified that AMFBM can reduce most of the unbalanced axial magnetic force as well as keeping torque ripple at a low level. In order to realize the AMFBM, finite control set model predictive control is adopted. A postfault model of dual-three-phase permanent-magnet machines with modified vector space decomposition method is first brought forward to predict the future behavior of the controlled variables with various voltage inputs. After that, a cost function is designed to track the desired winding current by evaluating all the predictions to decide the next step of the inverter. Experimental results show that the control scheme performs well in both dynamic and steady-state situations. [ABSTRACT FROM PUBLISHER]

Accurate knowledge of motor position is required in the motor drive application where smooth torque performance is needed. The error in position causes ripple in the developed current and thereby produce torque ripple. This paper analyzes the various effects of position sensor error in the current developed and in the torque generated in a current controlled permanent magnet synchronous motor drive. This research is focused on analyzing effect of position error on smooth production of torque in an interior permanent magnet synchronous motor (IPMSM) drive due to various inaccuracies. The analysis is verified through simulation and test results by measuring torque and torque ripple performances of an IPMSM drive. The results can be easily extended to surface mount permanent magnet motor drive also. [ABSTRACT FROM PUBLISHER]

To minimize the ripple on the dc-link current and torque due to carrier signal injections, conventional saliency based self-sensing control schemes using voltage and current carrier signals for interior permanent magnet synchronous machines (IPMSMs) are optimized in this paper. Carrier signal oriented coordinates are introduced to model the high-frequency behavior of IPMSMs and are used for the analysis and signal processing of proposed methods. Moreover, stability issues are discussed in this paper. Experimental results on a commercial high voltage inverter for application in hybrid and electrical vehicles confirm the applicability of the proposed methods. [ABSTRACT FROM AUTHOR]

Permanent magnet brushless dc (BLDC) machines are widely used due to various advantages such as high efficiency and high torque density, and therefore compactness as well as long expected lifetime. All of these benefits are of major interest when designing a drive for a small fan application of a few watts. This paper presents the design investigations of a small single-phase BLDC motor for such an application. Notably, it discusses different constraints which arise during the design process and which may be of special relevance due to the particular given power level and application. [ABSTRACT FROM PUBLISHER]

This paper presents a novel flux barrier design of a torque ripple reduction in a saliency-based sensorless drive concentrated-winding interior permanent magnet synchronous motor (IPMSM). The motor is designed for general-purpose sensorless industrial drives and to fulfill the torque ripple requirement with the required maximum torque under the sensorless drive. The designed rotor has a V-shape magnet, and a circular flux barrier at the rotor yoke in the center of N- and S-poles. A 45- \N\cdot \m –5.5-kW IPMSM has been manufactured to check the design validity. The validity of the proposed design procedure and the expected drive characteristics are experimentally verified by using the prototype. [ABSTRACT FROM PUBLISHER]

This paper mainly studies the effect of the winding layer number on the performance of interior permanent-magnet (IPM) synchronous machines equipped with fractional-slot concentrated windings (FSCWs) for electric vehicle applications. In order to quantitatively evaluate FSCW-IPM machines with different numbers of winding layers, three models with single-, double-, and four-layer winding configurations have been built to compare back electromagnetic force, average torque, torque ripple, core losses, copper losses, flux-weakening capability, overload capability, etc. Both theoretical and finite-element analysis results illustrate that multilayer windings yield lower $d$-axis inductance and weaker flux-weakening capability but better overload capability. It is also shown that torque ripple and core losses are significantly reduced in machines with multilayer windings. [ABSTRACT FROM AUTHOR]