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Electric machines are widely employed in a variety of sectors, including automotive and aerospace industry. With the rising trend towards electrification in aviation, electric machines with increased power density and efficiency are becoming key enabling technologies, requiring the development of innovative design procedures. In this study, a preliminary design procedure for Surface Mounted Permanent Magnet Synchronous Machines (SPMSMs) intensively cooled by means of oil channels placed in the stator slots is proposed. The analytical derivation of SPMSM sizing equations, including the sub‐domain model and optimisation algorithm will be reported in detail. Indeed, both the electromagnetic and thermal equations of the machine are considered for the derivation of the sizing tool. As a result, the latter allows to capture variation of the machine design not only in terms of mechanical demands, such as power and speed, but also in terms of coolant characteristics, and can be effectively employed to perform trade‐off studies at a preliminary design stage. The proposed design tool will be used for a specific case study: The design of a high‐speed machine for an aerospace hydraulic actuator. The accuracy of the proposed design tool is validated for different parameters by comparing the results to experimental measurements performed on an existing 8‐pole 9‐slot prototype SPMSM. [ABSTRACT FROM AUTHOR]

In high performance electric machines, the increase of fundamental frequency leads to additional losses in the winding due to parasitic effects such as the associated skin and proximity effects. In the first part, this paper presents an investigation into accurate modelling of AC losses in the winding using numerical methods and their experimental verification. Then, using experimental motorette setups, this research provides a comparative study between fixed strand positioning and fixed conductor shapes on the AC losses in the winding. It is shown that the exact position of strands in the conductor is not a critical factor; however, it is very important to control the conductor shape inside the slot. In the final section of this paper, an investigation into the relationship between AC losses in the winding and copper filling factor is presented. It is shown experimentally that counter-intuitive design choices such as using a lower copper fill factor and thicker strand diameters may be beneficial in achieving the highest overall efficiency. [ABSTRACT FROM AUTHOR]

This article proposes a modular approachto the power sharing control of permanent magnet synchronous bearingless machine. The selected machine topology features a winding layout with phases distributed into nonoverlapping three phase groups, a solution whose twofold aim is to increase the fault tolerance and to allow for the radial force generation. The three phase subwindings are supplied by standard three-phase inverter, leading to a modular system architecture. A throughout explanation of the methodology used to develop the control algorithm is presented considering the torque and force control in combination with the power sharing management of the machine. Special emphasis is placed on validating the modeling hypotheses based on a finite element characterization of the machine electro-mechanical behavior. The proposed control strategy is also extended to cater the possibility of one or more inverters failure, thus validating the intrinsic advantage of the redundancy obtained by the modularity of the system. An extensive experimental test campaign is finally carried out on a prototyped multi three-phase permanent magnet synchronous drive. The obtained results validate the bearingless power sharing operation in healthy and faulty scenarios, both at steady state and under extreme transient condition. [ABSTRACT FROM AUTHOR]

In an interior permanent magnet synchronous motor (IPMSM) with segmented skewed poles, the armature reaction magnetic field (AR-MF) changes nonlinearly due to the saturation of the rotor magnetic barrier. Meanwhile, this varies under different excitation currents. As a result, it is difficult to be calculated by means of analytical methods. In this paper, the calculation model of AR-MF of IPMSM is first established by vector superposition method, without considering the saturation effect of rotor and the slotting effect of stator. In the second step, the virtual magnetic field of the rotor is introduced to quantitatively calculate the influence of local inhomogeneous saturation on the AR-MF. The latter is derived by combining both the subdomain method and equivalent magnetic circuit method. The complex relative permeance is also introduced to establish the AR-MF accounting for the stator slotting effect. To validate the AR-MF calculation method proposed, an 8-pole 48-slot IPMSM with segmented skewed poles is considered as a case study, showing a comparison by both with finite element (FE) results and the electromagnetic torque measured on a test bench. The model proposed in this paper shows high accuracy and fast computation with respect to FE analysis. [ABSTRACT FROM AUTHOR]

In the last decade, the trend toward higher efficiency and higher torque density electrical machines (EMs) without permanent magnets (PMs) for the industrial sector has rapidly increased. This work discusses the latest research and industrial advancements in synchronous reluctance machines (SynRMs), being the emergent motor topology gaining wide acceptance by many industries. This article presents an extensive literature review covering the background and evolvement of SynRM, including the most recent developments. Nowadays, SynRM has found its niche in the EM market, and the reasons for that are highlighted in this work together with its advantages and disadvantages. The key journal publications in SynRM topics are discussed presenting the biggest challenges and the latest advancements with particular regards to the design methodology. This article aims to provide a thorough overview to the research community and industry about SynRM. There is a clear potential for SynRM to take over a significant portion of the EM market in the near future to meet efficiency standards in industrial applications without the use of rare-Earth PM technology. [ABSTRACT FROM AUTHOR]

This paper is focused on the design, optimisation and control of a permanent magnet assisted synchronous reluctance machine (PMaSynRel) for low cost high efficiency household appliances, in particular a motor for washing machine. The design and optimisation of the motor aims at maximising the torque produced and power factor, while minimise torque oscillations and the losses, thus improving the efficiency. A campaign of tests has been carried out on the prototype of the optimised machine, comparing finite element results and experimental measurements as a validation of the proposed design. In addition, torque ripple measurements are confirming that the solution proposed is meeting the optimisation design targets. The outcomes of this project are demonstrating that PMaSynRel drives are a suitable candidate for white goods sector, and that the proposed design is able to boost the performance and efficiency class with respect to the state-of-the-art solutions. [ABSTRACT FROM AUTHOR]

Due to the local inhomogeneous magnetic saturation of the core of the interior permanent magnet synchronous motor (IPMSM), the magnetic field changes nonlinearly, which makes the analytical calculation of the magnetic field difficult. Therefore, the calculation of the magnetic field mostly relies on the finite element method (FEM). However, the high computation cost of FEM restricts the efficiency of the design and analysis of IPMSM. In this article, an analytical model (AM) of slotless open-circuit air-gap magnetic field (OC-AG-MF) of IPMSM with V-shaped segmented skewed poles is derived by combining the subdomain method (SDM) and the magnetic equivalent circuit (MEC) method, and then, the AM of slotted OC-AG-MF of IPMSM with V-shaped segmented skewed poles is obtained by introducing the complex relative permeance. To show the effectiveness of the novel AM, the OC-AG-MF and cogging torque of an IPMSM with V-shaped segmented skewed poles for electric vehicles are calculated by the AM and FEM, respectively. The spatial order, amplitude–frequency characteristics, and the 3-D spatial distribution of the OC-AG-MF are analyzed. Finally, the accuracy of the AM is experimentally verified by direct measurement of OC-AG-MF and no-load back electromotive force (EMF) of the motor. The AM proposed in this article is shown to accurately calculate the radial and tangential components of OC-AG-MF of IPMSM with V-shaped segmented skewed poles considering rotor magnetic bridge saturation effect and stator slotting effect. Meanwhile, the efficiency of the design and analysis of the motor is expected to be improved due to the reduced computational effort compared to the prevalent FEM. [ABSTRACT FROM AUTHOR]

This article deals with the power-sharing control of bearingless multisector and multithree-phase permanent magnet machines. The proposed control strategy allows to distribute the power flows among the three-phase inverters supplying the machine during bearingless operation of the drive. The control technique is based on the extension of the vector space decomposition modeling approach. The components producing the electromagnetic torque, i.e., the q-axis currents, are controlled independently from the d-axis ones, also with the aim of managing the power flows among the three-phase systems. Conversely, the d-axis currents are exploited for the generation of the radial forces needed to levitate the rotor, while considering the compensation of the forces caused by the q-axis currents in case of unbalanced power sharing strategy. The validity of the proposed method is confirmed by simulations and experimental tests on a prototyped bearingless multisector permanent magnet synchronous machine. The proposed approach is a contribution to the development of advanced control systems employing multiphase drives in the field of bearingless and multiport applications. [ABSTRACT FROM AUTHOR]

This paper presents a novel design concept for Synchronous Reluctance (SynRel) machines aimed at reducing the torque ripple. Two general sizing approaches based on the homothetic scaling principle are defined and compared. An in depth analysis on the torque ripple, for a wide range of scaled geometries, evaluated by finite element, has been carried out at different operating conditions. A further analysis is performed on 4 scaled geometries that have been optimized starting from 4 random rotor geometries. It is shown that the main rotor geometrical variables converge to similar values for all scaled machines. The accuracy of the proposed model is then validated by comparing the FE simulated torque ripple waveforms with the experimental data carried out, for a range of operating conditions, on a machine prototype. The outcome of this work is a fast and accurate scaling technique for the preliminary design of SynRel machines with reduced torque ripple. [ABSTRACT FROM AUTHOR]

The performance of anisotropic electrical machines is strongly dependent on the current loop characteristics. The problems for achieving robustness and fast response, without overshoot and oscillations, are mainly related to different values and behavior of the direct and quadrature inductances ($L_d, L_q$), as well as to high output frequencies. In this article, a novel current controller structure based on internal model control method is presented, taking into account the magnetic anisotropy ($L_d\ne L_q$). The model of salient machines is derived directly in the discrete domain and used to obtain a model-based controller. The controller derivation does not rely on transport-delay approximations, which enables improved decoupling of axes dynamics and the closed-loop robustness for very high output frequencies. The presented controller enables enhanced response for higher current loop bandwidth and output frequencies than the state-of-the-art methods. The experimental verification is performed on a three-phase synchronous machine, using a standard industrial three-phase inverter. [ABSTRACT FROM AUTHOR]

Finite-set model predictive current control (FS-MPCC) has been employed for machine drives owing to the good dynamic performance. Sensitivity to parameter variation is one of the main barriers to its widespread application. To overcome this barrier, this article proposes an improved FS-MPCC for surfaced permanent magnet synchronous machines (SPMSMs). The contribution of this article is developing a novel current update mechanism, where the variation of resistance, rotor flux linkage, and inductance is considered, in which a modified coordinate system that contains a stationary and rotary axis frame is introduced. In this case, the predicted parameter can be obtained more accurately based on this mechanism, which can suppress the disturbances caused by model parameter mismatch. In addition, SPMSM parameter mismatch effect on FS-MPCC performance is analyzed in this article, which testifies that resistance mismatch influence on current prediction error can be neglected in practical system. The proposed FS-MPCC is validated and compared with different state-of-the-art methods. Improvement of the proposed control strategy is validated by means of experimental results on a 2-kW test rig. [ABSTRACT FROM AUTHOR]

In this article, a virtual cogging torque (VCT) control method to reduce the speed ripple of direct-drive permanent magnet synchronous machine servo system under low-speed conditions is proposed. Compared with other factors, at low speeds, the cogging torque is the main factor that deteriorates the drive performance, even induces speed oscillations. Especially in this article, due to volume limitation, the cogging torque is designed larger than normal one in order to remove the need of brake. Based on the model of permanent magnet synchronous motor, the cause and effect of the cogging torque are analyzed. Inspired by the characteristic of cogging torque, the VCT control method is proposed and investigated to significantly reduce the speed ripple at low speeds. The main idea of this proposed control method is to produce a proper VCT and continuously move the corresponding virtual stable equilibrium point to drive the rotor smoothly. In addition to the principle of this control method, its analysis and implementation are studied as well. Simulation and experimental results from the prototype demonstrate that the proposed control method is correct and valid, and it is simple and effective to smooth the speed at low-speed operations. [ABSTRACT FROM AUTHOR]

The rotor structure of synchronous reluctance machines (SynRel) is conventionally retained mechanically by iron ribs. In this paper, a novel structure for high-speed synchronous reluctance rotor is presented. The novelty of this paper is the proof of a concept of SynRel machine without iron ribs. Structurally, the rotor iron lamination segments are embedded in an adhesive resin material with high temperature resistance and mechanical strength. Three four-pole SynRel machines have been designed with the target of improving motor torque, and compared for different ribs configuration. It has been shown that the proposed motor performs enhanced torque, power factor, and efficiency with respect to conventional SynRel with iron ribs. An extensive sensitivity analysis of the ribless rotor geometry is carried out, followed by both mechanical analysis and experimental over speed test to guarantee its robustness above the operating speed range. The manufacturing procedure of this novel rotor is introduced. Finally, the experimental results on both SynRel prototypes are presented, showing the increase in torque, power factor, and efficiency of the proposed solution. This paper is a first step toward the definition of a viable and novel solution of SynRel machines with improved performance. [ABSTRACT FROM AUTHOR]

In this paper, a cost-effective and highly accurate resolver-to-digital conversion method is presented. The core of the idea is to apply a third-order rational fraction polynomial approximation for the conversion of sinusoidal signals into the pseudo linear signals, which are extended to the range 0°–360° in four quadrants. Then, the polynomial least squares method is used to achieve compensation to acquire the final angles. The presented method shows better performance in terms of accuracy and rapidity compared with the commercial available techniques in simulation results. This paper describes the implementation details of the proposed method and the way to incorporate it in digital signal processor-based permanent magnet synchronous motor drive system. Experimental tests under different conditions are carried out to verify the effectiveness for the proposed method. The obtained maximum error is about 0.0014° over 0°–360°, which can usually be ignored in most industrial applications. [ABSTRACT FROM AUTHOR]

The more electric aircraft concept aims to improve the fuel consumption, the weight, and both the maintenance and operating costs of the aircraft, by promoting the use of electric power in actuation systems. According to this scenario, electromechanical actuators for flight control systems represent an important technology in next generation aircraft. This paper presents a linear-geared electromechanical actuator for secondary flight control systems, where the safety and availability requirements are fulfilled by replicating the electric drive acting on the drivetrain. Indeed, the architecture considered consists of two power converters feeding as many electrical machines coupled to the same mechanical system. The design of both the permanent magnet synchronous machine and the power converter are addressed. Preliminary results on the electric drive prototype are also provided and compared to the design requirements. Finally, the electromechanical actuator performance at system-level is evaluated in Dymola environment, analyzing different operating modes. [ABSTRACT FROM AUTHOR]

An often-overlooked aspect during the development process of electrical machines is the validity and accuracy of the machine material properties being used at the design stage. Designers usually consider the data provided by the material supplier, which are measured on material in an unprocessed state. However, the fact that the machining processes required to produce the finished product (e.g., the stator core) can permanently vary the material properties is very often neglected. This paper, therefore, deals with and investigates the effects that such processes can have on the overall machine performance. To do this, three sets of material data, the material suppliers’ data, material data based on conventional characterization methods, and material data based on test samples that include the manufacturing processes, are used to develop three versions of the same baseline machine. The results of these three machines are then compared, and the resulting variations of the machine's performance are presented and described. The chosen baseline machine is a high-performance and relatively high speed, aerospace, electrical machine. Special attention is focused on the efficiency maps of the machine, as this aspect is highly dependent on the material properties that are the most sensitive to manufacturing processes such as the material's anhysteretic B–H curve and its specific core loss. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nd-Fe-B samples with comparable magnetic properties to the state-of-the-art were manufactured using laser powder bed fusion (L-PBF). • An investigation into the process-structure–property relationships in L-PBF of the Nd-Fe-B magnets is presented. • The L-PBF Nd-Fe-B is nanocrystalline consisting of melt pools with cores, boundaries and heat-affected zone (HAZ). • The printed samples suffered from micro-cracking attributed to residual stress. Two kinds of cracks were observed: (i) at the interfaces of the main phase and the precipitated phase and (ii) in the HAZ near the melt pool boundaries. Laser powder-bed fusion (L-PBF), as an additive manufacturing (AM) technique, has demonstrated excellent capabilities in achieving degrees of freedom in manufacturing that are otherwise unattainable. The potential of combining Nd-Fe-B as a permanent magnet and the manufacturing capabilities of L-PBF promises new prospects for functional AM in applications such as electric machines. In this study, high density L-PBF Nd-Fe-B samples (91%) with remanence of 0.65 T and maximum energy product of 62 kJ/m3 were successfully produced, comparable to the state-of-the-art in this field. A parametric study correlating the integrity of the parts to the process parameters, such as, the scan speed and hatch distance is presented. From a metallurgy perspective, the microstructure of the additively manufactured samples was different from the conventionally-sintered material. Interestingly, similarities to the microstructures of laser spot welded material were observed. The fabricated magnets mainly consisted of Nd 2 Fe 14 B with small fractions of precipitated phases and suffered from the presence of cracks at input energies sufficient for powder fusion. The relative density and integrity was constrained by the intrinsic brittle nature of the intermetallic Nd 2 Fe 14 B phase, the high energy input required to melt some phases, as well as the rapid heating and cooling rates experienced during processing. [ABSTRACT FROM AUTHOR]

Laser powder-bed fusion (PBF-LB), a class of additive manufacturing (AM), has attracted wide interest in the production of Nd-Fe-B permanent magnets, benefiting from the minimisation of waste of rare-earth elements and the post-processing requirements. Most research on PBF-LB Nd-Fe-B has focused on reducing defects in printed parts alongside the improvement of the resultant magnetic properties. Detailed analysis of the microstructure that results in permanent magnetic properties is yet to be published. In this research, a combination of high-resolution microstructural investigations was conducted for this purpose. For the first time, an in-depth analysis of the grain structure in terms of morphology, size distribution, and texture is presented and correlated to the permanent magnetic performance. Melt pools showed a hierarchical grain size distribution of primary Nd 2 Fe 14 B phase grains with a polygonal morphology and random crystalline alignment, in addition to a small amount of Nd-rich and Nd-lean precipitates in the matrix of the Ti-rich amorphous grain boundaries. The permanent magnetic properties of this material are mainly determined by the nanostructured Nd 2 Fe 14 B grains and the amorphous Ti-rich iron-based intergranular phase but could be weakened by precipitates that act as magnetic pores. Remelting during PBF-LB led to the transformation of the coarse grains of the previously solidified layer to fine ones, favourable for the permanent magnetic properties. The mechanisms of these complex phase formations and transformations during processing and the development of the nanocrystalline microstructure are elucidated in this paper as a basis for informing the optimisation process for microstructural development. [Display omitted] [ABSTRACT FROM AUTHOR]