Search Results (70)

This paper proposes a novel axially parallel salient pole hybrid excitation synchronous generator (PSPHESG) for small and medium hydropower (SMHP). To prevent irreversible demagnetization of the permanent magnets (PMs), while improving the power density and reducing the volume compared with those of a conventional electrically excited synchronous generator equipped with an AC exciter, a salient pole series hybrid excitation machine is axially integrated with an electrically excited machine, with the latter serving as the power compensation section. The basic structure and operating principles of the proposed PSPHESG are introduced. Finite-element analysis (FEA) is used to investigate the magnetic field distribution and no-load characteristics. Moreover, the phase angle deviation characteristics and output performances under load are analyzed, showing favorable voltage output capability over a wide load range during steady-state operation. Finally, the anti-demagnetization capability of the PM is studied under field forcing (FF) and de-excitation (DE). The results confirm that the PSPHESG not only provides good constant-voltage capability but also effectively avoids irreversible PM demagnetization during FF and DE, indicating its promising applicability to SMHP systems. Full article

In applications with a wide constant power speed range, the use of conventional permanent magnet machines is complicated by their uncontrolled magnetic flux, increased losses at high speeds, increased inverter current, and dangerous open circuit back EMF. For this reason, synchronous machines without magnets and with a field winding on the rotor are increasingly being used in traction applications. However, due to high electrical losses in the field winding, rotor cooling becomes a critical issue. An alternative is to use hybrid excited machines, which retain the advantages of electrically excited machines while significantly reducing rotor losses. This paper presents a comparison between a conventional electrically excited machine and a novel hybrid excited machine for traction applications with a wide constant power speed range of 9.3:1 (4200 to 450 rpm, mechanical power 23.6 kW). Both machines have the same external dimensions and were optimized using the same optimization algorithm. It is shown that the hybrid excited machine provides a reduction in rotor losses by 1.8–2.8 times depending on load conditions. Its total loss is also reduced, although its cost of active materials increased by a factor of 2.8 due to the use of permanent magnets. Full article

Conventional flux-reversal permanent magnet motors have problems such as excessive torque ripple and rich harmonic content in direct drive applications such as oil exploration, which restrict their application in high-precision scenarios. To address this issue, this paper presents a hybrid excitation topology that integrates double-armature windings, stator Halbach hybrid permanent magnet arrays, rotor-staggered unequal-tooth and rotor-hybrid permanent magnets. Two-dimensional finite element analysis was conducted using ANSYS Maxwell 2023 R1 to evaluate electromagnetic performance under rated steady-state conditions, rated power 300 kW, rated speed 83 rpm, rated voltage 660 V, rated phase current 307 A, and axial core length 200 mm. The simulation results show that the proposed topology has an average output torque of 34.5 kN·m at rated conditions compared with the traditional flux-to-reverse permanent magnet motor of the same size, and the torque ripple rate is reduced from 27.5% to 17.4%, a relative reduction of 36.8%. The results are based only on numerical simulation and have not been verified by physical prototype experiments. Dynamic control strategies, multi-load transient responses and experimental verification will be carried out in subsequent work. Full article

Wound Field Synchronous Motors (WFSMs) offer precise control over the rotor magnetic field, making them well suited to electric vehicle (EV) traction applications that require adjustable excitation, wide constant-power operation, and freedom from rare-earth permanent magnets. The excitation system (ES) governs the rotor field strength and therefore directly influences motor efficiency, dynamic response, and operational stability. This paper reviews modern excitation strategies for WFSMs in EV traction, with particular emphasis on contactless approaches based on wireless power transfer (WPT). The fundamental principles of inductive power transfer (IPT) and capacitive power transfer (CPT) are presented, together with their design considerations, compensation topologies, power electronic interfaces, control strategies, and practical challenges, followed by a discussion of hybrid IPT–CPT systems. Representative experimental studies in each category are compared on the basis of power level, efficiency, operating frequency, and misalignment tolerance. A capacitive power coupler is also designed for a WFSM, which requires a 6-amp DC field current, where the geometry of the coupler is constrained by the WFSM rotor geometry. The review identifies open challenges—including misalignment sensitivity, electromagnetic interference, thermal constraints, and air-gap variability under rotation—and outlines research directions for compact, efficient, and reliable WPT-based excitation systems for next-generation EV traction motors. Full article

Axial–radial flux permanent magnet synchronous machines (ARFPMSMs) are an emerging family of electrical machines that combine radial flux and axial flux topologies within a single electromagnetic structure. By using multiple radial and axial air gaps, they increase the effective torque-producing surface without enlarging the machine envelope, which enables higher torque density and better utilization of active materials than in conventional single-flux topologies. This makes them attractive for traction, aerospace, wind, elevator and other compact high-torque applications. This paper reviews the state of the art of ARFPMSMs and provides four main contributions. First, it proposes a unified topology-oriented classification of classical PM-only, hybrid-excitation and vernier/flux-modulated ARFPMSMs, while clarifying their conceptual boundary with transverse-flux machines. Second, it consolidates published designs and compares key parameters across the three families. Third, it summarizes experimentally validated prototypes, including rated power, torque density, materials and cooling methods. Finally, it identifies open research challenges and outlines future directions, including surrogate models, Bayesian optimization and active cooling strategies. Full article

The increasing demand for electric power in hybrid electric aircraft platforms prompts the development of multi-megawatt generators featuring high specific power, compactness and intrinsic fault tolerance. Air-core machines constitute a promising solution to overcome the magnetic saturation and mass limitations of conventional iron-core designs. This paper presents a comparative electromagnetic design study of two air-core synchronous generator topologies for aircraft applications, namely a permanent magnet machine with a Halbach array rotor and an electrically excited synchronous machine featuring a high-temperature superconducting field winding. Both the generators are designed for identical output and adopt a double three-phase stator winding to enhance safety and redundancy. The Halbach array machine is used as the reference configuration representative of a technologically mature solution, whereas the superconducting generator targets high magnetic loadings by means of the superconducting excitation, to minimize the active volume. The solutions proposed in this paper are developed in the frame of a national (Italian) research project dedicated to the study of stages of multi-megawatt fault-tolerant aircraft generators. Full article

In this paper, the concept of symmetry is utilized to optimize the structural parameters and output characteristics of the generator design—that is, the construction and solution of the equivalent magnetic circuit method for the hybrid excitation generator are symmetrical. To address the issues of high excitation loss and low power density in purely electrically excited generators, as well as the difficulty in adjusting the magnetic field in purely permanent magnet generators, a new topology for a built-in permanent magnet and salient-pole electromagnetic hybrid excitation generator is proposed. Firstly, an equivalent magnetic circuit model of the generator is established. Secondly, expressions are derived to describe the relationships between the dimensions of the salient-pole rotor and the permanent magnets and the generator’s no-load induced electromotive force, cogging torque, and air gap flux density. These expressions are then used to analyze the structural parameters that influence the generator’s performance. Thirdly, optimization targets are selected through sensitivity analysis, with the no-load induced electromotive force, cogging torque, and air gap flux density serving as the optimization objectives. A multi-objective genetic algorithm is employed to optimize these parameters and determine the optimal structural matching parameters for the generator. As a result, the optimized no-load induced electromotive force increased from 18.96 V to 20.14 V, representing a 6.22% improvement; the cogging torque decreased from 177.08 mN·m to 90.52 mN·m, a 48.88% reduction; the air gap flux density increased from 0.789 T to 0.829 T, a 5.07% improvement; and the air gap flux density waveform distortion rate decreased from 6.22% to 2.38%, a 39.3% reduction. Finally, a prototype is fabricated and experimentally tested, validating the accuracy of the simulation analysis, the feasibility of the optimization method, and the rationality of the generator design. Therefore, the proposed topology and optimization method can effectively enhance the output performance of the generator, providing a valuable theoretical reference for the design of hybrid excitation generators for vehicles. Full article

Currently, electric machines predominantly rely on costly rare-earth NdFeB magnets, which pose both economic and environmental challenges due to rising demand. This research explores recent advancements in machine topologies and magnetic materials to identify and assess promising solutions to this issue. The study investigates two alternative machine topologies to the conventional permanent magnet synchronous machine (PMSM): the permanent magnet-assisted synchronous reluctance machine (PMaSynRM), which reduces magnet usage, and the wound-field synchronous machine (WFSM), which eliminates magnets entirely. Additionally, the potential of ferrite and recycled NdFeB magnets as substitutes for primary NdFeB magnets is evaluated. Through detailed simulations, the study compares the performance and cost-effectiveness of these solutions against a reference permanent magnet synchronous machine (PMSM). Given their promising performance characteristics and potential to reduce or eliminate the use of rare-earth materials in next-generation electric machines, it is recommended that future research should focus on novel topologies like hybrid-excitation, axial-flux, and switched reluctance machines with an emphasis on manufacturability and also novel magnetic materials such as FeN and MnBi that are currently seeing synthesis challenges. Full article

This paper presents a comparative study between two permanent magnet motor structures, one with trapezoidal waveforms and the other with sinusoidal waveforms, from the perspective of production cost, dynamic characteristic performance, and energy economy. The novel element of the research is also in using an electromagnetic converter to reduce the vehicle’s overall energy consumption and to push the multiple disadvantages of using the insolated bipolar transistors. This study is based on the sizing of the electromagnetic converter and the two motor structures using the method of combined analytical finite elements. The program for sizing is coupled with two control laws relating to the motor types in order to choose the top performers according to good dynamic characteristics and energy saving. The simulation results show, on the one hand, the equivalence of these structures from a dynamic characteristic point of view and, on the other hand, that the trapezoidal waveform motor structure is more economical. The design of an excitation system optimizing the consumed energy equipped by a hybrid excitation motor is also developed. Full article

The instability in rare-earth material supply and rising costs have driven research into rare-earth-free electric motors. Among various alternatives, wound rotor synchronous motors (WRSMs) stand out due to their adjustable excitation, enabling high torque at low speeds, and efficient field weakening at high speeds. Unlike permanent magnet synchronous motors (PMSMs), WRSMs offer greater operational flexibility and eliminate the risk of demagnetization. However, accurately modeling WRSMs remains challenging, especially when considering axial fringing flux and leakage components, which significantly affect motor performance. To address this challenge, this paper proposes a 3D nonlinear magnetic equivalent circuit (MEC) model that explicitly incorporates axial flux components and leakage paths in WRSMs with overhang rotor structures. Unlike conventional 2D MEC models, which fail to capture axial flux interactions, the proposed approach improves prediction accuracy while significantly reducing computational costs compared to full 3D finite element analysis (FEA). The model was validated through comparisons with 3D FEA simulations and experimental back-EMF measurements, demonstrating its accuracy and computational efficiency. The results confirm that the 3D nonlinear MEC model effectively captures axial flux paths and leakage components, making it a valuable tool for WRSM design and analysis. Future research will focus on further refining the model, incorporating hysteresis loss modeling, and developing hybrid MEC–FEA simulation techniques to enhance its applicability. Full article

In this paper, a new fault-tolerant consequent-pole hybrid excited (FTCPHE) machine with toroidal winding (TW) is designed for electric vehicles (EVs). In this proposed machine, U-type permanent magnets (PMs) are adopted in the consequent-pole rotor with the sequence of PM–iron–PM–iron. The stator tooth placed in the stator is classified into two groups to achieve hybrid excitation. The TW is positioned on the stator yoke to achieve the simple structure and excellent fault-tolerant ability. First, the topology of this proposed FTCPHE machine with the TW is briefly introduced and compared to that with the traditional combined winding. Second, the operation principle, the magnetic circuit, and the design procedure of the FTCPHE machine are analyzed and illustrated. Third, several key structural parameters of the proposed FTCPHE machine are discussed and designed to improve electromagnetic performances. Next, some electromagnetic properties, including the flux distribution, the no-load back-EMF, the electromagnetic torque, the cogging torque, and the fault-tolerant ability, are discussed in detail. Finally, a prototype of this proposed FTCPHE machine is manufactured to validate the simulated results. Full article

To improve the flux regulation range of the Axial–Radial Flux Hybrid Excitation Machine (ARFHEM) and the utilization rate of permanent magnets (PMs), the effects of different length–diameter ratios (LDRs) on the ARFHEM performance are studied. Firstly, the principle of the flux regulation of the ARFHEM is introduced by means of the structure and equivalent magnetic circuit method. Then, based on the principle of the bypass effect, the analytical formulas of LDRs, the number of pole-pairs, and the flux regulation ability are derived, and then the restrictive relationship between the air-gap magnetic field, LDR, and the number of pole-pairs is revealed. On this basis, the influence of an electric LDR on motor performance is studied. By comparing and analyzing the air-gap magnetic density and no-load back electromotive force (EMF) of motors with different LDRs, the variation in the magnetic flux regulation ability of motors with different LDRs is obtained and its influence mechanism is revealed. In addition, the torque regulation ability and loss of motors with different LDRs are compared and analyzed, and the influence mechanism of the LDR on torque and loss is determined. Finally, the above analysis is verified by experiments. Full article

An axial field hybrid excitation synchronous generator (AF-HESG) is proposed for an independent power supply system, and its electromagnetic performance is studied in this paper. The distinguishing feature of the proposed generator is the addition of static magnetic bridges at both ends to place the field windings and the use of a sloping surface to increase the additional air-gap cross-sectional area. The advantage of the structure is that it achieves brushless excitation and improves the flux-regulation range. The structure and magnetic circuit characteristics are introduced in detail. Theoretical analysis of the flux-regulation principle is conducted by studying the relationship between field magnetomotive force, rotor reluctance, and air-gap flux density. Quantitative calculation is performed using a magnetomotive force (MMF)-specific permeance model, and the influence of the main parameters on the air-gap flux density and flux-regulation range is analyzed. Subsequently, magnetic field, no-load, and load characteristics are investigated through three-dimensional finite element analysis. The loss distribution is analyzed, and the temperature of the generator under rated conditions is simulated. Finally, a 30 kW, 1500 r/min prototype is developed and tested. The test results show good flux-regulation capability and stable voltage output performance of the proposed generator. Full article

Hybrid-excited generators have a wide voltage regulation capability or a wide range of variable-speed constant-voltage output capability, providing a significant advantage in the new energy power generation field. To achieve the optimal design of brushless hybrid excitation synchronous generators with third harmonic excitation, it is necessary to grasp the influence of design parameters on excitation power accurately. Firstly, this paper elaborates on the structure and principle of the hybrid excitation synchronous generator. From the perspective of excitation power generation, the expression for excitation power in hybrid excitation generators has been derived, identifying the primary factors influencing excitation power, which include winding parameters, structural parameters, and magnetic circuit saturation. Secondly, qualitatively calculate the influence of the number of turns and arrangement, turns in rotor harmonic, air gap length, and thickness of the permanent magnet on the excitation power, which is verified by the electromagnetic field finite element method. The results showed that the use of full pitch and a moderate increase in turns, a decrease in air gap length, and an increase in the thickness of the permanent magnet can all increase the rotor excitation power. A brushless hybrid excitation synchronous generator prototype based on third harmonic excitation was developed, the correctness of theoretical analysis and calculation were verified by test results. Full article

According to the different excitation methods, automotive eddy current retarders (ECRs) can be divided into electrically excited retarders (EERs) and permanent magnet excited retarders (PMERs), and EERs and PMERs have certain complementarity in control and braking characteristics. Therefore, based on literature research, this article proposes a hybrid excitation rotary electromagnetic retarder (HERER) and conducts numerical simulation analysis and experimental research on the braking performance of the HERER. Firstly, the structure and working principle of the HERER are introduced. Secondly, based on the principles of electromagnetics, an equivalent magnetic circuit analysis model of the HERER is established. Then, a finite element analysis model of the HERER is established using Jmag 14 electromagnetic simulation software, and the braking performance of the HERER under different current and speed conditions is studied. Finally, bench tests are conducted on the air loss torque and eddy current braking performance of the HERER. The effectiveness of the finite element analysis model and equivalent magnetic circuit model of the HERER is verified. Full article