Search Results (84)

This paper proposes a harmonic screening-based method for calculating the cogging torque of the axial flux permanent magnet synchronous motor. The magnetic field energy in the air gap is derived from the air gap flux and the magnetomotive force of rotor. The cogging torque is then obtained using the energy-based method. Compared with finite element analysis, the proposed approach is significantly faster while maintaining high accuracy. It is particularly effective for scenarios involving stator staggering, which can facilitate quick calculation of cogging torques of many different staggering angles, offering rapid insights into motor performance during the initial design. The method achieves a similarity accuracy with FEA results and reduces computation time, demonstrating both its efficiency and reliability. Full article

This paper proposes a vibration reduction method for fractional slot concentrated winding (FSCW) permanent magnet synchronous motors (PMSMs) by applying a four-layer winding configuration. The radial electromagnetic force (REF), particularly its low space-harmonics, causes significant vibration in PMSMs. These low-order REF components are influenced by sub-harmonics in the airgap magnetic flux density (MFD), which occur at frequencies lower than the fundamental component generated by the armature magnetomotive force (MMF) in FSCW PMSMs. To mitigate these sub-harmonics in the MFD, the four-layer winding is applied to the FSCW PMSM. As a result, the overall vibration of the motor is reduced. To verify the effectiveness of the four-layer winding, both electrical and mechanical characteristics are compared among motors with conventional one-, two-, and, proposed, four-layer windings. Finally, the three motors are fabricated and tested, and their vibration levels are experimentally evaluated. Full article

This paper proposes an E-core outer-rotor hybrid-excitation flux switching (OR-HEFS) machine for in-wheel direct driving application. According to the general air gap field modulation theory, the magneto-motive force (MMF) permeance model was established to investigate the air gap flux density, and then the torque generation, the flux regulation principle, and the excitation-winding-induced voltage of the E-core OR-HEFS machine were analyzed. To characterize the output performances, the influence of the design parameters was investigated for the E-core OR-HEFS machine, including the split ratio, stator tooth arc, PM arc, fault-tolerant tooth arc, rotor tooth arc, stator yoke width and rotor yoke width. The performances contained the output torque, torque ripple, flux regulation ratio, and the excitation-winding-induced voltage. On this basis, the aforementioned four performances were optimized by means of the non-dominated sorting genetic algorithm II (NSGA-II). Based on the optimization result, a prototype was manufactured and tested to verify the whole investigation of this paper. 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

The drive system of an electric car must meet road requirements related to overcoming obstacles and driving dynamics depending on the class and purpose of the vehicle. The driving dynamics of modern cars as well as size and weight limitations mean that wheel hub motors operate with relatively high current density and high power supply frequency, which may generate significant power losses in the windings and permanent magnets and increase their operating temperature. Designers of this type of motor often face the need to minimize the motor’s weight, as it constitutes the unsprung mass of the vehicle. Another limitation for motor designers is the motor dimensions, which are limited by the dimensions of the rim, the arrangement of suspension elements and the braking system. The article presents two directions in the design of wheel hub motors. The first one involves minimizing the length of the stator magnetic core, which allows for shortening of the axial dimension and mass of the motor but involves increasing the thermal load and the need for deeper de-excitation. The second one involves increasing the number of pairs of magnetic poles, which reduces the mass, increases the internal diameter of the motor and shortens the construction of the fronts, but is associated with an increase in the motor operating frequency and increased power losses. Additionally, increasing the number of pairs of magnetic poles is often associated with reducing the number of slots per pole and the phase for technological reasons, which in turn leads to a greater share of spatial harmonics of the magnetomotive force in the air gap and may lead to the generation of higher power losses and higher operating temperatures of permanent magnets. The analysis is based on a simulation of the motor operation, modeled on the basis of laboratory tests of the prototype, while the car is driving in various driving cycles. Full article

Driven by frequency conversion, the windings of a three-phase permanent magnet synchronous motor (PMSM) contain both odd and even harmonic currents. Due to the motor’s pole–slot conductance modulation, the interaction between the magnetic fields generated by these harmonic currents and the permanent magnet field results in harmonic radial vibrations of the motor. This paper analyzes the three-phase currents of the prototype and derives the radial magnetomotive force (MMF) spatiotemporal models for symmetric harmonic currents. By integrating Maxwell’s magnetic force formula and vibration response formula, the radial vibration models for symmetric harmonic currents are developed. The characteristics of vibrations caused by odd and even harmonic currents, as well as positive sequence and negative sequence harmonic currents, are analyzed separately. A cyclic sequence, low-frequency vibration suppression control method incorporating multiple harmonic current injections was designed. Experimental results of this method are compared with those obtained using an ideal sinusoidal current. Except for the second harmonic vibration, all other vibrations are significantly suppressed, with a maximum suppression rate of 92.28%. The total vibration level is reduced by 12.7619 dB, and the average torque is reduced by 0.67% with the total harmonic distortion of the current at 2.89%. The experimental results show that the vibration method in this paper has little influence on the average torque of the motor, the current distortion rate is small, and the vibration suppression effect is good. Full article

Winding inductance always plays a key role in the electromagnetic performances of stator surface-mounted permanent magnet (SSPM) machines, including their flux-weakening capability, prospective fault current, power factor, current ripple, etc. Generally speaking, winding inductance mainly comprises three components: an air-gap component, a slot-leakage component, and an end-leakage component. In this paper, firstly, the winding pole pairs of SSPM machines are investigated based on the magneto-motive force-permeance model, through which the winding configurations can also be determined. Then, according to the winding configurations, three analytical expressions for each inductance component are derived to evaluate the winding inductance per phase. In addition, finite element analysis (FEA) is employed to verify the effectiveness of the derived analytical expressions. Meanwhile, three prototyped SSPM machines are manufactured, and their winding inductances are measured to further verify the analytical expressions. The measured results agree with both the analytical and FEA results very well. Full article

Utilizing non-overlap windings has emerged as a favourable choice for minimizing electrical machine manufacturing costs, among other benefits. Nevertheless, it is widely acknowledged that these windings exhibit a notable level of harmonic contents in the resultant magnetomotive force, which can detrimentally impact machine performance, particularly in terms of torque ripple. In the context of wind energy conversion, maintaining low torque ripple is an essential and demanding prerequisite. Medium-speed wind generators present a good trade-off between high energy yield and low gearbox ratios. So far, medium-speed non-overlap winding wound-rotor synchronous generator (WRSG) technologies have been limited to 10/12 and the less common 16/18 pole/slot combinations. In this study, the analysis of a high-pole number combination (24/27 pole/slots) non-overlap WRSG is carried out to theoretically and comparatively predict the electromagnetic and radial force mechanical stress performance analysis with the 16/18 machine with a phase-shifted non-overlap winding (PSW), at 5 MW power level. The study, which is founded on the finite element analysis (FEA) technique, shows that the 24/27 machine exhibits comparable average torque and torque ripple, lower core losses and significantly reduced radial forces compared to the 16/18 PSW-WRSG. However, the 16/18 PSW-WRSG has a 50% reduction in the radial forces compared to the conventional 16/18 non-overlap winding. Experimental vibration analysis of a 3 kW 16/18 WRSG test machine confirms the radial force and vibration reduction in the phase-shifted winding. Full article

The present work aims to optimize the magnetomotive force and the end-winding leakage inductance from a discrete distribution of conductors in electrical machines through multi-objective particle swarm heuristics. From the development of an application capable of generating the conductor distribution for different machine configurations (single or poly-phase, single or double layer, integral or fractional slots, full or shortened pitch, with the presence of empty slots, etc.) the curves of magnetomotive force and the end-winding leakage inductance associated with the winding are computed. Taking as an optimal winding the one that presents, simultaneously, less harmonic distortion of the magnetomotive force and less leakage inductance, optimization by multi-objective particle swarm was used to obtain the optimal electrical machine configuration and the results are presented. Full article

This article proposes a new connection method of tapped inductors that works in the current source, which enables the current-mode power converter circuit to have a new topological relationship. Usually, in a switched-inductor circuit, a stable output multiple is obtained through the connection of the inductor and the switching devices. This is because the tapped point on the inductor varies, and the magnetomotive force (mmf) of inductance is adjusted. Thereby, the output current is controlled by the states of switching devices within a certain range. This optimized circuit structure can adjust the output current according to load changes in practical applications without changing the input power supply. The proposed method has been verified for its feasibility through detailed analysis and hardware work. The principal analysis based on the flux linkage and the PSIM simulation confirms that the theoretical circuit can be implemented. Finally, a hardware circuit is built to obtain real and feasible conclusions, and it is verified that the circuit can achieve a stable output and variable current within a specific range. The proposed work presents an alternative power conversion methodology using the active switching of mmf, and it is a stable and simple power conversion technique. 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

The study presents an efficient computational investigation on the behaviour of the direct-drive system integrated into the offshore 5 MW NREL wind turbine model under demanding aerodynamic loading conditions with the aim of optimising and developing more sustainable key structural components. The research was based on computational simulation packages in order to verify the use of real-world wind data and the loading conditions on the blade structures through aero-elastic simulation studies as well as analyse the behaviour of the drive system. Through the application of validated aerodynamic loading conditions, resulting normal forces on the blades structure were obtained and applied to a dedicated simplified model that was also previously validated to estimate the transferred loads into the powertrain. The adopted methodology allowed for the identification of shaft misalignment induced air gap eccentricity. The impact of shaft deflections on resulting magnetomotive force was considered by making use of the Maxwell stress distribution expression. By taking into account the resulting loading cases on the generator structure, as well as the inherent typical loads generated by the electrical machine, a procedure including structural parametric and topology optimisation was developed and performed, achieving a rotor mass reduction between 8.5 and 9.6% compared to the original model. Full article

The article presents the solution of a power rectifier system dedicated to cooperating with an electric generator based on a special synchronous generator, which can be used in wind or water energy systems. In this generator, a pair of three-phase windings in a stator is utilized. One of the windings is connected in a star, and the second one is connected in a delta configuration. Two six-pulse uncontrolled (diode) rectifiers are included at the outputs of the windings. The rectifiers are coupled by a pulse transformer. The primary windings of this transformer are supplied by a power-electronics current source called a current modulator. With the help of this current modulator, the quasi-sinusoidal magnetomotive force (mmf) in the stator of the machine can be obtained. Additionally, to improve the efficiency of the described system, the low-power transistor rectifier, which is connected to the DC bus of the current modulator, has been used. With the help of this converter, it is possible to control and stabilize the voltage level in a DC circuit. It works, in this case, in inverter mode. The principle of working and elaborated control methods of the current modulator and the additional rectifier are presented. Selected results of simulation and experimental tests are also presented. Full article

This paper offers a novel dual-mode double stator wound rotor synchronous machine for variable speed applications. The proposed motor integrates the benefits of both the traditional wound rotor synchronous machine (WRSM) and brushless wound rotor synchronous machine (BL-WRSM). A constant torque can be attained in the maximum torque per ampere region by operating the proposed machine as a traditional WRSM in Mode I, and a constant power can be attained in the field-weakening region by operating it as a BL-WRSM in Mode II. Moreover, due to the dual-stator structure, the proposed machine exhibits improved performance in terms of high torque density as compared to the existing single stator BL-WRSM. By using a special stator winding arrangement to achieve the sub-harmonic component of the stator magnetomotive force, the brushless operation of the proposed machine is achieved. The additional sub-harmonic component induces a voltage in the harmonic winding placed on the rotor, which is then rectified and provided a DC current to field winding for brushless excitation. In order to validate the effectiveness of the proposed machine, a two-dimensional finite element analysis (FEA) is carried out. Full article

The aim of this paper is to present our research into the reduction of vibrations in induction motors. The use of power inverters results in the generation of electrical harmonics, which increase the level of the mechanical vibrations of electrical machines. To reduce these harmonics, we present a discontinuous pulse-width modulation (PWM) control strategy based on carrier-wave modulation applied to multilevel inverters. Using the proposed modulation technique, the amplitude of the electrical harmonics is reduced, as compared to other conventional techniques. These current harmonics produce the MMF (magnetomotive force) harmonics in the air gap, which are one of the main sources of vibrations. The control strategy makes it possible to vary the electrical spectrum at the output of a multilevel inverter by modifying a control parameter of the carrier wave in the PWM, thus avoiding the natural frequencies of mechanical resonance. The proposed technique also has the feature of attenuating the total harmonics distortion of the voltage of the multilevel inverters, as well as the achievement of a higher RMS value of the output voltage for the same DC level. Laboratory results for an induction motor with different modulation strategies, applied in a multilevel inverter and compared to the strategy presented, are attached. Full article