Search Results (47)

This paper investigates the dependencies between the design parameters of the armature (stator) winding of a high-speed PMSM machine and the electrical losses in its windings resulting from eddy currents. In addition, the factors accounting for the occurrence of parasitic circulating currents, whose presence in the phase windings is associated with the design specificity, are analyzed. Quantitative analysis is carried out by the application of a newly developed mathematical model for the calculation of fundamental and additional losses in a multi-turn coil enclosed in the slots of a ferromagnetic core. The analysis takes into account the actual design of the slot and the conductor, the variable arrangement of individual conductors in the slot, the core saturation and the presence of the excitation field—to represent the main factors that affect the process of additional losses in the slot of the electric machine. The verification of the mathematical model developed in this study was carried out by comparing the distribution of power losses in the slot section of the coil, consisting of several elementary conductors connected in parallel and located in a rectangular open slot, with an identical distribution derived on the basis of an analytical method from the classical circuit theory. For the purpose of confirming the results and conclusions derived from simulation studies, a number of physical experiments were carried out, consisting in determining the power losses in multi-turn coils of different designs. Recommendations have been developed to minimize additional losses by optimizing the arrangement of conductors within the slot, selecting the appropriate cross-sectional size of a single conductor and the saturation level of the tooth zone. Full article

This paper introduces a novel field-oriented control (FOC) strategy for an open-end stator three-phase winding induction motor (OEW-TP-IM) using dual space vector modulation-pulse width modulation (SVM-PWM) inverters. This configuration reduces common mode voltage at the motor’s terminals, enhancing efficiency and reliability. The study presents a backstepping control approach combined with a mean value theorem (MVT)-based observer to improve control accuracy and stability. Stability analysis of the backstepping controller for key control loops, including flux, speed, and currents, is conducted, achieving asymptotic stability as confirmed through Lyapunov’s methods. An advanced observer using sector nonlinearity (SNL) and time-varying parameters from convex theory is developed to manage state observer error dynamics effectively. Stability conditions, defined as linear matrix inequalities (LMIs), are solved using MATLAB R2016b to optimize the observer’s estimator gains. This approach simplifies system complexity by measuring only two line currents, enhancing responsiveness. Comprehensive simulations validate the system’s performance under various conditions, confirming its robustness and effectiveness. This strategy improves the operational dynamics of OEW-TP-IM machine and offers potential for broad industrial applications requiring precise and reliable motor control. Full article

This study presents a detailed investigation of the torque-speed characteristics of a WEG single-phase squirrel-cage induction motor (SPSCIM) of (1/2 hp), 110/220 V at 60 Hz. The primary objective was to derive the motor’s equivalent circuit and validate its performance curves through finite element analysis (FEA), simulation using MATLAB^®/Simulink^®, and experimental testing. Finite element simulations were conducted using the software FEMM (Finite Element Method Magnetics) to model the magnetic flux distribution within the motor’s stator and rotor. These simulations, based on the motor’s dimensions and nameplate data, provided essential insights into the electromagnetic behavior, including flux density and saturation effects, which are crucial for accurate torque-speed curve predictions. For experimental validation, tests were performed under open-circuit and locked-rotor conditions through a universal machine as a load emulator. The torque-speed characteristics were determined using the Suhr method and the classical approach, with the resulting curves compared to experimental measurements. Voltage and current were measured using AC PZEM-004T and DC PZEM-017 meters, while rotor speed was monitored with a Hall effect sensor (A3144). The results revealed strong agreement between the FEM simulations, Surh method, and experimental data, demonstrating the reliability and accuracy of the combined simulation and analytical methods for modeling the motor’s performance. The estimations using classical and Suhr methods, Simulink simulations, and FEMM yielded low error percentages, mostly below 2%. However, in the FEMM simulation, rotor resistance showed a higher error of around 20% due to unavailable data on the exact number of windings turns, a modifiable parameter that can be corrected through further adjustments in the simulation. The torque-speed curves obtained at different voltage levels showed an excellent correlation, confirming the effectiveness of the proposed approach in characterizing the motor’s operational behavior. Full article

This paper investigates the performance of a five-phase silicon carbide (SiC)-based current-source converter (CSC) integrated with a Doubly Fed Induction Generator (DFIG) for wind energy applications. The study explores both healthy and faulty operation, focusing on system behavior under transient conditions and various load scenarios in stand-alone mode. A novel five-phase space vector PWM strategy in dual coordinate planes is introduced, which enables stable control during normal and open-phase fault conditions. Experimental results demonstrate improved stator voltage and current quality, particularly in terms of reduced Total Harmonic Distortion (THD), compared to traditional voltage-source converter-based systems. Furthermore, the system maintains operational stability under a single-phase open fault, despite increased oscillations in stator quantities. The results highlight the potential of five-phase CSC-DFIG systems as a robust and efficient alternative for wind power plants, particularly in configurations involving long cable connections and requiring low generator losses. Future work will focus on enhancing fault-tolerant capabilities and expanding control strategies for improved performance under different operating conditions. Full article

High-torque-density motors are essential in humanoid, wearable, and rehabilitation robots due to their ability to minimize gear ratios, improve back-drivability, and support compact joint design. However, their inherently high back-EMF limits speed performance, and safety regulations often constrain supply voltages to below 50 V in human-interactive environments. To overcome these limitations, this study introduces a novel winding strategy called parallel open-end winding (POEW), which combines the benefits of two individual approaches: Parallel Connected Winding (PCW) and Open-End Winding (OEW). PCW reduces phase resistance and inductance, thereby mitigating voltage drop and back-EMF, while OEW eliminates the neutral point, allowing full-phase voltage utilization. Experimental results show that the POEW configuration achieves a 3.5-fold increase in maximum speed compared to the conventional Series-Connected Winding (SCW), without altering the rotor or stator structure. Torque constant measurements confirm that all proposed configurations maintain torque output with minimal variation. Although the motor constant slightly decreases due to the higher current in parallel paths, the significant speed enhancement under low-voltage conditions demonstrates the practicality and effectiveness of POEW for advanced robotic applications requiring both high torque and speed. Full article

This paper proposes a two-dimensional (2D) generalized equivalent magnetic network (GEMN) model suitable for surface-mounted permanent magnet electric machines (SPEMs). The model divides the SPEM into eight types of regions: stator yoke, stator tooth body, stator tooth tips, stator slot body, stator slot openings, air gap, rotor permanent magnets, and rotor yoke. Each region is subdivided radially and tangentially into multiple 2D magnetic network units containing radial and tangential magnetic circuit parameters, forming a regular magnetic network covering all regions of the SPEM. The topology of this magnetic network remains unchanged during rotor rotation and can accommodate various surface-mounted permanent magnet structures including Halbach arrays, which enhances the generality of the model significantly. The proposed model can be used to calculate the 2D magnetic flux density distribution, winding electromotive force, electromagnetic torque, stator iron loss, and permanent magnet demagnetization in the influence of magnetic saturation, stator slotting, and current harmonic. Comparative analysis with the accurate subdomain method (ASDM) and finite element method (FEM) demonstrates that the GEMN model achieves a good balance between computational speed and accuracy, making it particularly suitable for efficient electromagnetic performance evaluation of SPEMs. Full article

The dual-stator permanent magnet (DSPM) machine has proved to have high space utilization and a redundant structure, which can be beneficial to improving the fault tolerance and torque density performance. In this paper, three types of DSPM machines are proposed and compared, where two sets of armature windings are wound in both inner/outer stators, producing more than one torque component compared with single-stator PM machines. The machine topology and operating principle of three DSPM machines are analyzed first. Next, feasible stator/rotor-pole number combinations are compared and determined. Furthermore, based on the finite-element (FE) method, both the electromagnetic performances of three DSPM machines under open-circuit and rated-load conditions after optimization are compared, aimed at generating maximum torque at fixed copper loss. The FE analyses indicate that the dual-stator consequent-pole permanent magnet (DSCPPM) machine generates maximum torque per PM volume, together with relatively high efficiency, which makes it a potentially hopeful candidate for low-speed and high-torque applications. In addition, a thermal analysis is carried out to confirm the validity of the design scheme. Finally, in order to verify the FE predictions, a prototype DSCPPM machine is manufactured and experimentally tested. Full article

Servo motors are among the most efficient and precise performers within the category of permanent magnet synchronous motors. These motors stand out for their high power density, quiet operation, low maintenance, and wide operating speed range advantages. One of the disadvantages of these motors, which is also the subject of this study, is their high torque ripple. Torque ripple is critical in applications requiring precision, as it can affect operational performance and contribute to vibration and noise issues. Torque ripple can be reduced through design methods such as different winding layouts, slot openings, stator/rotor skewing, or pole offset. In this study, torque ripple of servo motors was investigated through various magnet geometry designs and analyses using the finite element method. Design and analysis studies were conducted for a reference servo motor, and alternative designs were obtained by modifying the rotor structure of the reference motor. In the studies conducted, it has been observed that the torque ripple, initially at 2.17 Nm, can be improved to as low as 1.23 Nm. This indicates that the torque ripple, which was initially at 3.75%, can be reduced to around 2.08%. However, performance losses may occur depending on the extent of improvement. Full article

Permanent magnet eddy current heating as a new type of wind energy utilization method, which is energy-saving, is zero-emission, and involves no pollution and a high utilization of wind energy, has attracted more and more attention. This paper deals with the simulation and optimal design of a permanent magnet eddy current heater (PMECH) driven by wind. Solid steel, closed-slot, and open-slot PMECH are proposed, and corresponding 2D finite element method (FEM) models are established. Using the skin depth concept, numerical analyses are conducted on the influence of the number, size, and position of copper strips on the thermal power of closed-slot and open-slot PMECHs, and the thermal power growth compared to solid steel PMECH. The results showed that there is an optimal value for stator wall thickness. When the air-gap length is 0.5 mm and the rotation speed is 200 and 1000 rpm, the optimal stator wall thickness is 16 and 9 mm, respectively. Compared to the influence of conductivity on thermal power, the influence of permeability is more significant. Compared with solid steel PMECH, both closed-slot and open-slot PMECH in a low-speed region can effectively improve thermal power, and the open slot has more obvious advantages. The maximum values of the thermal power growth (TPG) and thermal power growth rate (TPGR) of the closed-slot PMECH are 1.57 kW and 120.15%, respectively. The maximums of TPG and TPGR of the open-slot PMECH are 2.58 kW and 175.08%, respectively. The experimental results prove the validity of the analytical calculation. Full article

This paper investigates the use of fractional-slot concentrated windings (FSCWs) in large-scale (MW level) offshore wind generators. It focuses specifically on a power rating of 3 MW and uses an existing direct-drive synchronous PM machine (DD-SPM) with 480s/160p and dual three-phase integer-slot winding (ISW) as a baseline. A multiple of the common 12s/10p FSCW machine is used that matches the electrical frequency of the ISW machine, yielding a 192s/160p dual three-phase machine. The hybrid star–delta connection has grown increasingly popular owing to its unique harmonic cancellation properties, which can help reduce rotor and PM eddy current losses in FSCW machines. In this paper, two dual three-phase star–delta-wound machines are scaled to 3 MW and included in the investigation. Specifically, a 384s/160p dual three-phase and dual star–delta winding machine, which is a multiplication of the 24s/10p machine, and a 192s/176p dual three-phase and dual star–delta winding machine, which is a multiplication of the 24s/22p machine, are used. These machines are investigated using finite element analysis (FEA) and compared on the basis of their air-gap flux density harmonics, open-circuit electro-motive force (EMF), torque performance, and losses and power. It is found that the proposed 384s/160p dual star–delta winding machine has the best electromagnetic performance of all, with a stator power that is 1.2% greater than that of the baseline ISW machine. However, this machine has a coil pitch of 2 and so loses the manufacturing and fault-tolerant advantage of having concentrated windings. If concentrated windings are desired, then the proposed 192s/176p dual star–delta winding machine is the best choice, with the stator power only 2.6% less than that of the baseline ISW machine, but unfortunately still has significant rotor and PM eddy current losses. Full article

This article aims to realize the brushless operation of a wound rotor vernier machine (WRVM) by a third-harmonic field produced through stator auxiliary winding (X). In the conventional model, a third-harmonic current is generated by connecting a 4-pole armature and 12-pole excitation windings serially with a three-phase diode rectifier to develop a pulsating field in the airgap of a machine. However, in the proposed model, the ABC winding is supplied by a three-phase current source inverter, whereas the auxiliary winding (X) carries no current due to an open circuit. The fundamental MMF component developed in the machine airgap creates a four-pole stator field, while the third-harmonic MMF induces the harmonic current in the specialized rotor harmonic winding. The rotor on the other side contains the harmonic and the field windings connected through a full-bridge rectifier. The electromagnetic interaction of the stator and rotor fields generates torque. Due to the open-circuited winding pattern, the proposed machine results in a low torque ripple. A 2D model is designed using JMAG-Designer, and 2D field element analysis (FEA) is carried out to determine the output torque and machine’s efficiency. A comparative performance analysis of both the conventional and proposed topologies is discussed graphically. The quantitative analysis of the proposed topology shows better performance as compared to the recently developed third-harmonic-based brushless WRVM topology in terms of output torque and torque ripples. Full article

This paper focuses on analyzing asymmetric and open-phase fault modes in symmetrical two-channel six-phase induction machines while considering the spatial harmonics of the electromagnetic field in the air gap. Under sinusoidal power supply, the magnetomotive force exhibits high-order spatial harmonics, which arise due to the winding design. The interaction between these spatial harmonics and the first-time harmonic of the power supply results in the presence of high-order harmonics in the current and electromagnetic torque. The harmonic content of the currents and torque under asymmetric and open-phase operation mode while taking into account spatial harmonics is analyzed. It is shown that in asymmetrical modes, in addition to the 5th, 7th, 11th, and 13th higher harmonics found in symmetrical modes, harmonics in multiples of the 3rd are introduced into the stator winding currents. As for the composition of the electromagnetic torque in asymmetrical modes, all even harmonics are present, in addition to the 6th and 12th harmonics that are characteristic of symmetrical modes. A mathematical model of the six-phase induction machine has been developed using the average voltages within the integration step method. Its adequacy was verified by comparing the simulation results with the experimental results obtained from the developed prototype. Full article

This paper evaluates the performance of an inverter-fed nine-phase squirrel cage induction motor (SCIM) under faulty conditions. The induction motor’s stator core of the conventional National Electrical Manufacturers Association (NEMA) frame size of 90L has been rewound to accommodate coils that form the nine-phase windings. The prototyped nine-phase SCIM drive has been tested for transient and steady-state capabilities for well-conditioned and defective functioning. The open-phase-winding faults are caused by fuses opening during an imposed short circuit. The experimental results evidenced that the nine-phase induction motor drive can operate under faulty conditions while minimizing the gravity of defective functioning. This premise has positioned the nine-phase SCIM drive as a strong candidate in applications where fault tolerance is a must, and the motor may be required to continue operating temporarily under faulty conditions until maintenance is in effect. Full article

The series-winding permanent-magnet synchronous motor (SW-PMSM) has the merits of high output power and excellent control performance, as does the open-winding permanent-magnet synchronous motor (OW-PMSM). Meanwhile, it can greatly reduce the number of power devices. However, due to the existence of the zero-sequence path, zero-sequence current occurs, which can cause additional losses and torque ripples. Thus, this paper proposes a novel direct torque-control strategy for the SW-PMSM with zero-sequence current suppression capability (ZSCS-DTC). First, the series-winding topology (SWT) and the voltage vector distribution in the SW-PMSM drives are analyzed. Secondly, the basic DTC (B-DTC) scheme for the SW-PMSM is investigated, and the defects of zero-sequence current open-loop control in the B-DTC scheme are revealed. Thirdly, a new voltage vector synthesis scheme is proposed for suppression of zero-sequence current while ensuring bus voltage utilization. A switching table is reconstructed with the newly synthesized voltage vectors. On this basis, a ZSCS-DTC scheme for the SW-PMSM is proposed based on zero-sequence current closed-loop control so that electromagnetic torque, stator flux linkage and zero-sequence current can be controlled simultaneously. Finally, the effectiveness of the proposed ZSCS-DTC scheme for the SW-PMSM drives is verified. Full article

In a typical inverter-fed AC drive system, the stator windings carry a current with a large harmonics content, resulting in an increased AC loss. In this paper, the additional copper losses caused by non-sinusoidal currents are investigated for different magnet wire topologies, including the flat conductor, stranded, and litz wires. Also, a two-slot simplified model is introduced for accurate prediction of the AC losses at high frequency. It is found that one of the major issues of the conventional copper coil is that the losses are not uniformly distributed across the slot, and over 70% of the losses are concentrated near the slot opening. Moreover, using the transient finite element method, different winding topologies and arrangements are simulated at the stranded level to evaluate the losses and current density for each strand under highly distorted currents. Furthermore, different coil samples are prototyped for the same slot geometries to compare their performance under the same pulse-width modulation (PWM) waveforms for a wide range of frequencies. Finally, new hybrid coil topologies are proposed, which employ different magnet wires or materials within the same slot. The results demonstrate that utilizing a mixed wire configuration can effectively mitigate the adverse effects of eddy current losses. This approach can yield up to 16–41% lower losses while also achieving a weight savings of 36–70%. Full article