Search Results (71)

Wound-rotor synchronous machines (WRSMs) offer a promising, magnet-free alternative for safety-critical transportation sectors like electric vehicles (EVs) and marine propulsion. While multiphase structures enhance fault tolerance in these applications, conventional WRSMs still suffer from reliance on maintenance-prone slip rings and brushes. Brushless multiphase self-excitation presents a compelling solution, but it introduces a critical design challenge: ensuring decoupled control between the torque-producing (αβ) and magnetizing () subspaces to prevent severe performance degradation. To address this cross-coupling issue, this paper proposes a 20-slot/18-pole five-phase architecture. By exploiting distinct spatial harmonics, the stator generates two independently controlled magnetic fields with a dedicated rotor harmonic winding. An integrated diode rectifier then seamlessly converts the induced AC voltages into the required DC field excitation. Extensive finite-element analysis (FEA) using ANSYS Maxwell is conducted to validate the design and rigorously evaluate subspace cross-coupling. Simulation results confirm that the proposed machine meets design specifications, demonstrating stable self-excited operation, acceptable efficiency, and representative fault-tolerant operation under a single open-phase condition, thereby confirming the electromagnetic feasibility of the proposed topology as a promising magnet-free candidate for future alternatives to PMSM-based traction solutions. Full article

All rotating electrical machines are susceptible to vibrations arising from electromagnetic (EM) forces, electrical faults, mechanical defects, imbalance, and structural resonance. In Doubly Fed Induction Generators (DFIGs), such electromechanical vibrations are especially important because they can degrade reliability, increase noise, and lead to severe damage if resonance-prone operating conditions are not identified in time. Although fault diagnosis in DFIGs has been widely investigated using current, voltage, and flux signatures, comparatively fewer studies have examined fault-specific vibration behaviour under stator and rotor interturn faults (ITTFs), particularly through a coupled EM structural framework. In addition, prior vibration-based studies have not examined the influence of end winding ITTFs, its location, severity, and modal interaction investigating resonance risk. This paper considers vibration characteristics of a variable-speed 2.8 MW DFIG used in a grid-connected Type-3 wind turbine unit (WTU) at no-load operating condition. The DFIG is modelled in ANSYS Academic Research v 2022 R2 Maxwell for EM behaviour assessment for ITTFs in both stator and rotor windings along with modal analysis (MA) in ANSYS Workbench to examine the undamped stator and rotor modes over a range of frequencies. This coupled approach enables identification of vibration signatures associated with different ITTF types. The results show the magnetic flux density near faulty end-winding region increases with fault severity and ranges from 4.19 T to 4.39 T in proximity to faulty windings. A dominant modal frequency band of 60–65 Hz is identified, where stator and rotor modes coincide, creating probable resonance conditions. A severe vibration response is observed for single-phase stator ITTF, showing an amplitude of 2116 mm/s at 480 Hz for a larger number of shorted turns, indicating that asymmetric faults can produce stronger EM excitation than multi-phase faults. The main contribution of this paper is demonstration of a fault-specific, MA and vibration-based Condition monitoring system (CMS) implementation workflow for a DFIG. Unlike prior vibration-based studies that primarily focus on general machine vibration, mechanical faults, bearings, etc., this paper links stator and rotor ITTF induced EM excitation to modal characteristics, resonance behaviour, and measurable vibration signatures, establishing vibration analysis (VA) as a practical complementary technique for CMS of ITTFs in DFIGs. Full article

This paper presents a robust fault-tolerant control (FTC) strategy for a multiphase PMSM-based propulsion system. The proposed approach combines an innovative super-twisting sliding mode controller (IST SMC) with a fault-tolerant model of the machine when an open-circuit fault occurs. The electrical propulsion system mainly has a two-line structure with a single DC source, a five-leg inverter and a Five-Phase Permanent Magnet Synchronous Motors (5-Φ PMSM), suitable for marine propulsion applications. Two main scenarios are investigated in this work. Firstly, if an open-phase fault occurs in one of the two 5-Φ PMSMs, a reconfiguration step of the machine control is applied in order to improve the performance of the propulsion system and to ensure the continuity of operation. Then, if the fault occurs in one of the two inverters, the faulty one is removed and the electrical series connection is made between the two machines, where they are powered by a single five-arm inverter, thus ensuring the continuity of operation of the system. Considering these two scenarios, a comparative analysis is made between the IST SMC and the classical PI controllers in terms of robustness to uncertainties, external disturbances and tracking accuracy for healthy and faulty operation modes, and during transient states. Full article

Gas–liquid–solid (G-L-S) mechanically agitated reactors are commonly used in chemical, pharmaceutical and bioprocessing applications due to their low operating costs and controlled and effective mixing. Computational Fluid Dynamics (CFD) is a powerful tool that enhances the understanding of flow dynamics, phase interactions and reactor performance. However, the CFD modeling of G-L-S mechanically agitated reactors is not extensively studied in the literature due to complex multiphase interactions, along with reactor design variations. This paper provides a critical synthesis of the literature, offering an overview not only of G-L-S stirred tank CFD modeling approaches but also of practical guidance on their selection and validation. Emerging high-resolution experimental techniques such as Electrical Resistance Tomography (ERT) coupled with pressure transducers, and Machine Learning (ML) models combined with experimental data, look promising to overcome current three-phase validation limitations. Future work to enhance predictive capabilities and reactor design and operation includes developing real-time digital twins, physics-based ML models and/or hybrid CFD-ML models. Full article

Many electromechanical specialists have attempted to move away from the classical method of designing windings of electrical machines using the star of slot electromotive forces, but their approaches are not always simple or universal. This article proposes a straightforward algorithmic method of winding synthesis based on number theory, which makes it possible to compute the distribution table of symmetrical multiphase, multimodular windings. Analytical expressions are provided for determining the assignment of coils to the corresponding phases, phase zones, and winding modules by sampling coils from a closed-ring structure. The method allows one to determine the direction of coil connections within a phase and covers both overlapping and non-overlapping windings. Three characteristic cases of the relationship between the number of coils and the number of pole pairs in multiphase alternating-current electrical machines are analyzed from the perspective of number theory. Conditions for implementing symmetrical windings are presented. The distribution factors of modular windings for higher field harmonics are evaluated. To validate the approach, examples of application and experimental results are provided. Full article

Multiphase electric drives (EDs) offer important advantages for high-demand applications. However, they require appropriate high-performance control strategies. In this context, finite-control-set model predictive control (FCS-MPC) emerges as a promising strategy, offering a notable flexibility to implement multiobjective regulation schemes. When applied to multiphase EDs, standard FCS-MPC exhibits degraded current quality at low and medium control frequencies. Multivector solutions address this issue by properly combining multiple voltage vectors within a single control period to create the so-called virtual voltage vectors (VVVs). In this way, this approach achieves flux and torque regulation while minimizing current injection into the secondary subspace. For this purpose, the VVV synthesis typically prioritizes active vectors with low contribution in secondary subspaces, avoiding the average deception phenomenon. VVV solutions commonly enable an open-loop regulation of secondary currents. Nevertheless, the absence of closed-loop control in the secondary subspace hinders the compensation of nonlinearities, machine asymmetries, and unbalanced conditions in the ED. Considering this scenario, this work implements a multivector FCS-MPC recovering closed-loop control for the secondary subspace. The capability of the proposal to mitigate secondary current injection and compensate for possible dissymmetries is experimentally evaluated in a six-phase ED. Its performance is compared against a benchmark technique in which secondary current regulation is handled in open-loop mode. The proposed control solution significantly improves in current quality, achieving a reduction in harmonic distortion of 54% at medium speed. Full article

The aim of the article is to determine the control range of a multiphase squirrel cage induction generator with more than three stator phases, operating in a wide range of driving speeds. The generator produces an output DC voltage using a multiphase converter operating as a PWM rectifier. The entire speed range is divided into intervals in which the sequence of stator phase voltages and, in effect, the number of pole pairs, is changed. In each interval, the output voltage is regulated by the frequency and amplitude of the stator voltages causing the highest possible power efficiency of the generator. The system can be scalar controlled or regulated using field orientation. Generator characteristics are calculated based on the set of steady-state equations derived from differential equations describing the multiphase induction machine. The calculation results are compared with simulations and with the steady-state measurement of the vector-controlled nine-phase generator. Recognizing the reliability of the obtained results, calculations are performed for a twelve-phase generator, obtaining satisfactory efficiency from 70% to 85% in the generator speed range from 0.2 to 1.0 of the assumed reference speed of 314 rad/s. The generator producing DC voltage can charge an electrical energy storage system or can be used directly to provide electrical power. This solution is not patented. Full article

The present paper deals with a review on bearing currents in electrical machines, with major emphasis on mechanisms, impacts, and mitigation strategies. High-frequency common-mode voltages from the inverter-driven system have been found to be the main reason for bearing current leading to motor bearing degradation and eventual failure. This paper deals with bearing currents—electrical discharge machining (EDM) currents, circulating bearing currents, and rotor-to-ground bearing currents—and the various methods of their generation and effects that are harmful to the bearings and lubricants of a motor. Mitigation techniques, among which the following have been taken into account, are studied in this context: the optimization of PWM modulation, and the use of shaft grounding brushes, insulated bearings, and passive or active filters. Finally, advantages, limitations, and implementation challenges are discussed. A review comparing three-phase and dual three-phase inverters showed that, due to the increased degree of freedom in modulation strategies, it is possible to eliminate common-mode voltages through active modulation techniques. Such added flexibility will reduce the risk of bearing currents effectively. It also highlights future research directions in bearing current suppression, including the development of multi-phase motor systems, real-time monitoring technologies with artificial intelligence, and the use of new insulation materials for the enhancement of bearing reliability. The results obtained should guide future research and engineering practices in suppressing bearing currents to improve motor durability with high performance. Full article

The growing demand for higher reliability and efficiency in modern electric drives, coupled with the increasing adoption of multi-phase machines, has necessitated advancements in fault-tolerant control strategies. This paper presents a fault tolerance analysis for a six-phase permanent magnet synchronous machine (PMSM) connected to a five-level cascaded H-bridge converter, employing a level-shift pulse width modulation (LSPWM) technique. Unlike existing strategies, this work integrates a unique combination of three key innovations: first, a fault detection mechanism capable of identifying faults in both machine phases and inverter legs with high precision; second, an open-circuit fault compensation strategy that dynamically reconfigures the faulty inverter phase leg into a two-level topology to reduce losses and preserve healthy switches; and third, a modified closed-loop control method designed specifically to mitigate the adverse effects of short-circuit faults while maintaining system stability. The proposed approach is validated through rigorous simulations in Simulink and Hardware-in-the-Loop (HIL) tests, demonstrating its robustness and applicability in high-reliability applications. Full article

The paper presents a comprehensive overview of recent advancements in power electronics and electric machine design, focusing on novel topologies, semiconductor technologies, and integrated design techniques for electric drives. New drive topologies are gradually moving from the research phase to practical application, aiming to increase the rated power, efficiency, and reliability of electric drives. Specifically, these topologies can be categorized into series, which focus on increasing the operating voltage; parallel, which aim at enhancing the operating current and adding redundancy; and multiphase, known for offering significant benefits such as improved fault tolerance, higher torque generation, the possibility of synthetic loading, and diverse winding layout options. Emerging wide bandgap semiconductors, such as silicon carbide and gallium nitride, allow for operation at higher frequencies and lower power losses, enabling further drive integration. In terms of design practices, higher computational power, supported by advanced software, enables simulation and analysis in multiple domains (thermal, mechanical, electromagnetic) using multiphysics co-simulation, as well as multi-objective optimization concepts to achieve rapid prototyping of optimized drive systems. All the approaches described are important steps towards further improving electric drives for numerous applications in industry, consumer electronics, and transportation. Full article

Nowadays, electric propulsion system implementation in vehicles is popular, and many studies and prototypes have been accomplished in this field. Aircraft are important members of the vehicle family, and Unmanned Aerial Vehicles (UAVs) are part of this family as well. Some UAVs still have conventional propulsion systems, which are less efficient and are harmful to the environment. In addition, conventional systems are vulnerable to faults in their propulsion system components. To overcome these problems, we designed a multi-phase Brushless Direct Current (BLDC) motor, to achieve fault-tolerant operation. Our designed BLDC motor was implemented in a UAV model that was created on MATLAB Simulink, based on a currently used UAV. Our design and performance analysis are shown for the BLDC motor, both standalone and as implemented in the created UAV model. The electric propulsion system performance is shown, according to the determined flight profile. We observed that the designed electric machine is capable of producing the required torque to create thrust for lifting the UAV. There are some advantages and disadvantages to using the designed electric machine in this class of UAV. This is shown in the related sections. Full article

The control of electric drives is an important topic due to the wide-spread use of such devices. Among these, multi-phase induction machines are gaining momentum in variable-speed applications. The usual control practice is the use of a speed Proportional–Integral loop that sets the current reference for an inner controller. This inner controller decides the voltage to be applied, which is realized by an electronic power converter. This paper presents an Artificial Intelligence (AI) scheme for tuning. It aims to optimize the usual figures of merit for drives. Moreover, tuning for both loops is tackled concurrently. The adjustment is performed relying on the operating region to address non-linear behavior. The results obtained using a five-phase induction motor illustrate that the proposed method can work in the entire operating range of the drive with improved results. Full article

New aerodynamic aircraft concepts enable the storage of volumetric liquid hydrogen (LH2). Additionally, the low temperatures of LH2 enable technologies such as the superconductivity of electrical fan drives and power distribution components. An increased power density of the onboard wiring harness and the electrical machine can be expected. The highest system efficiency and the smallest fuel and tank weight will be achieved with a highly efficient energy conversion by the fuel cell from LH2 to electrical energy. This publication shows a comprehensive study for cryogenic fan drives based on experimental-driven tape superconductor investigations, mission profile-based considerations, design analyses of superconducting electrical machines, and studies of the cooling concepts. A cryogenic system cannot be considered without a feasible cooling concept. Here, an approach with a safe He-based cooling system is proposed, using the LH2 flow to the fuel cell as a heat sink for the losses in the electrical system. Full article

In this article, to enhance the power output capability and system efficiency during charging, an approach to motor winding optimization for HEFS machine-based integrated on-board charging systems is proposed and analyzed. Firstly, the design process of the HEFS motor and the power electromagnetic components are analyzed to find the entry point for the integrated system optimization. Then, the comprehensive optimization process for the winding parameters of the HEFS motors in the integrated charging system is presented. Moreover, an integrated system based on a five-phase HEFS motor is used as an example for simulation verification. Finally, an experimental platform is built based on a 5 kW five-phase HEFS prototype. The experimental results are consistent with the simulation results. Therefore, the proposed comprehensive optimization method for windings can make the motor more suitable for building an integrated on-board charging system without affecting the electromagnetic performance of the motor. The optimization results indicate an improvement in output power and efficiency of the system in charging mode. Full article

The widespread diffusion of electric vehicles poses new challenges in the field of fault diagnostics. Past studies have been focused mainly on machines designed for industrial applications, where the operating conditions and requirements are significantly different. This work presents a review of the most recent studies about fault diagnosis techniques in electrical machines feasible for traction applications, with a focus on the most adopted approaches of the last years and on the latest trends. Considerations about their applicability for electric vehicle purposes, along with some areas that require further research, are also provided. Full article