Stator Yoke Research Articles

Vibration Performance Analysis of a Yokeless Stator Axial Flux PM Motor with Distributed Winding for Electric Vehicle Application

This article presents a detailed analysis of the electromagnetic force and vibration behavior of a new axial flux permanent magnet (AFPM) machine with a yokeless stator and interior PM rotor. Firstly, the configuration of an AFPM machine with a dual rotor and a sandwiched stator is introduced, including the structural design, fixation of the yokeless stator and segmented skew rotor structure. Then, the influence of anisotropic material and a fixed structure on stator modes is analyzed, including elastic modulus, shear model, the skew angle of slot and the thickness of stator yoke. Furthermore, a new non-equally segmented skew rotor structure is proposed and calculated for the reduction in vibration based on the multiphysics model. Three different segmented skew rotor schemes are compared to illustrate the influence of reducing vibration and noise. The predicted results show that the effect of the non-equally segmented skew rotor on reducing vibration is better than the other two schemes. Finally, a 120 kW AFPM motor is experimented with and the result matches well with the predicted data. The vibration performance of the AFPM motor with a dual rotor and sandwiched yokeless stator is revealed comprehensively.

Mathematical model for calculating steady-state conditions and static characteristics of salient-pole synchronous machines

Salient-pole synchronous machines occupy a paramount position in both the generation and consumption of electrical energy. Recent achievements in the design, manufacturing, and operation of salient-pole synchronous machines are the result of successful advancements in the fields of electromechanical engineering technology, semiconductor technology, and mathematical modeling. To calculate the nominal steady-state operation of salient-pole synchronous machines and their static characteristics (no-load, angular, V-shaped, regulatory, and external), a mathematical model has been developed. Its computer implementation enhances the technical and economic performance of synchronous pole machines. During the creation of the mathematical model, the following assumptions were made: the magnetic field of the machine is conditionally divided into a working field and scattered fields; the magnetic field of the machine is flat and parallel; the magnetic field in the active layer has only a radial component, while in the stator and rotor yokes, only a tangential one; the winding conductors are located in an infinitely thin layer and distributed along the slot according to a harmonic law; losses in the steel are absent. To create the mathematical model of salient-pole synchronous machine, a system of equations for the electrical and magnetic state is formulated. To obtain equations with coefficients independent of the rotor position, the coordinate transformation method (transformation to the dq0 rectangular coordinate system stationary with respect to the rotor) was employed.

Core loss determination in electric machines using short‐time transient thermal measurements

AbstractThis paper introduces a novel application of the inverse modelling method, which is designed to estimate core losses in both the stator and rotor regions of an electrical machine. The technique focuses on the use of short‐term transient temperature measurements obtained from the stator core of a slotless induction machine, with a focus on validating the measured temperature rise through a forward model. The measurement setup involves two primary approaches: (i) the use of thermal sensors embedded in a printed circuit board inside the stator core and (ii) surface sensors embedded on the stator yoke. Through the use of this innovative approach, the results indicate that the inverse modelling technique is highly effective in predicting core losses based on short‐time transient temperature rise measurements.

Rotor design optimization of a 4000 rpm permanent magnet synchronous generator using moth flame optimization algorithm

The goal of this paper is to optimize the rotor design parameters of 4000 rpm permanent magnet synchronous generator. The factors namely embrace, offset, outer diameter, and magnet thickness are selected as the design parameters those will be optimized in order to hold the magnetic flux density (MFD) distribution and the flux density on stator teeth and stator yoke within a desirable range while maximizing efficiency. The numerical simulations are carried out in the Maxwell environment for this purpose. The mathematical relationships between the responses and the factors are then derived using regression modeling over the simulation data. Following the modeling phase, the moth flame optimization is applied to these regression models to optimize the rotor design parameters. The motivation is determining mathematical relation between the important design parameters of the high speed generator and the measured responses, when standard M530-50A lamination material is used and then to demonstrate the utility of MFO to the readers on this design problem. The optimum factor levels for embrace, offset, outer diameter, and magnet thickness are calculated as 0.68, 30, 161.56, and 8.92 respectively. Additionally, confirmations are done by using Maxwell and the efficiency is calculated as 94.85%, and magnetic distributions are calculated as 1.64, 0.26, and 0.93 Tesla for stator teeth flux density, stator yoke flux density, and MFD; respectively. The results show that the efficiency is maximized and the magnetic distributions are kept within an appropriate range.

Optimization design of brushless DC motor based on improved JAYA algorithm

Brushless direct current motor is widely used in industrial production because of its simple structure, wide speed range and low noise. To improve the operation efficiency of brushless DC motor and reduce the production and application costs, the optimization of brushless DC motor is analyzed by introducing the JAYA algorithm. This method determines the optimal parameters of a brushless DC motor using the theory of electromagnetic structure parameter selection and efficiency calculation. The population diversity of the JAYA algorithm is improved through an empirical learning strategy, and an adaptive strategy is introduced to balance the development ability and search performance of the algorithm. This ensures population diversity and improves convergence speed. The experiment showcases that the improved JAYA algorithm has a lower rank average in unimodal function operations, demonstrating stronger local development ability and better stability. It exhibits strong search ability in many local optima of multimodal functions. Moreover, the motor's average efficiency after optimization is 94.48%. The algorithm reaches the global optimum after approximately 40 iterations and offers faster convergence speed and higher accuracy. The adaptive JAYA algorithm is stable at around 93% when the number of iterations reaches 90, with a maximum efficiency of 95.3%. It is 5–12 percentage points higher than the other three comparison algorithms. The optimal solution of the motor parameters in the adaptive JAYA algorithm is closest to the theoretical parameter optimization value, meeting both the constraints of variables and the constraints of the model. The stator diameter, tooth magnetic induction, winding current density, air gap magnetic induction, and stator yoke magnetic induction values are 201.5 mm, 1.8 T, 2.049 A/mm2, 0.63 T, and 0.91 T, respectively. The research overcomes the problem of parameter optimization in the optimization design of brushless DC motor, improving their economic value of brushless DC motor in industrial production and application.

Influence of the Cast Iron Frame on the Distribution of the Magnetic Field in the Stator Yoke and Additional Power Losses in the Induction Motor

Induction motors are a significant consumer of electricity. Therefore, their energy efficiency level plays a vital role in the world’s energy balance. The world’s markets strive to produce motors of efficiency class IE3 or IE4 while maximizing the use of wire and magnetic materials. However, high induction values in the motor core can also lead to significant losses in construction materials, especially in the magnetic motor housing. This article aimed to show how it is possible to determine the distribution of the magnetic field and additional losses in the yoke and the cast-iron motor frame using field-circuit methods to model the motor and to refine the analytical method for calculating these losses at the motor design stage.

Magnetic Coupling Effect and Performance Analysis of Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Power Generation

To eliminate slip rings, brushes, and terminate gear-box mechanism, ferrite permanent magnet (PM) based counter rotating dual rotor PM flux switching generator (CRDRPMFSG) for direct drive counter rotating wind turbine (D <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CRWT) application is proposed in this paper. Initially, the mechanism of gearless and brushless counter rotating wind power generation is discussed, and a simplified formulation opted for the slot/pole combinations. The proposed CRDRPMFSG encapsulate inner and outer machines with circumferentially magnetized PM enclosed by non-overlapped armature windings; thus, offering reduced overhang with compact design. However, co-axially linking the inner and outer machines through a shared stator yoke results in serious issues of magnetic coupling due to dual air-gap fields. To this end, eight topologies with various slot/pole combinations are comprehensively investigated using finite element analysis (FEA) for magnetic coupling effects and its influence on electromagnetic performance. From the analysis, it is shown that magnetic coupling level influence electromagnetic performance i.e., average torque, ripple rate, power factor, efficiency, losses, and output power. Moreover, it is noted that coupling level can be reduced by adopting same stator teeth in inner and outer machines or same stator teeth with different rotor poles. Finally, the predicted FEA calculations are verified experimentally with four benchmarked CRDRPMFSG prototypes.

Operating characteristics and design parameter optimization of permanent magnet linear generator applied to free-piston energy converter

A tubular permanent magnet linear generator (PMLG) with axial magnetized is proposed for the free-piston engine generator (FPEG). The structures and test rigs of the PMLG and FPEG prototypes are introduced. The working characteristics of the PMLG in FPEG system are analyzed under ignition conditions. A 2D finite element model of the PMLG is designed and verified based on initial design parameters and test results. The influences of key operating parameters on the output performance of PMLG are studied. On these basis, when considering the actual motion characteristics of the PMLG in FPEG system, the effects of different structural parameters on the power generation performance and efficiency (h) are investigated. Results show that when the working frequency of the FPEG is relatively small, the displacement profile resembles a sinusoidal curve. As the working frequency and stroke length increase, the power generation increases rapidly. As the air gap length and back iron shaft diameter decrease, and the stator slot number increases, the output voltage (U), current (I), power (Pout), and total loss power (Ploss) show an approximately linear increasing trend. As the pole arc coefficient and stator tooth width increase, the U, I, Pout, and Ploss first increase and then decrease. As the stator yoke thickness increases, the U, I, and Pout increase rapidly and then tend to stabilize. Besides, these structural parameters have little impact on power generation efficiency of this PMLG.

Analysis and Experimental Verification of the Tangential Force Effect on Electromagnetic Vibration of PM Motor

In traditional analysis, several studies have discussed the vibration behavior of electric machines from the point of view of radial force. With the increasingly strict vibroacoustic index, the tangential force effects on the vibration are analyzed and investigated, and it shows the contribution of tangential force on electromagnetic vibration cannot be ignored. However, these studies are based mainly on finite element multi-physics models, and experiments are not conducted. Furthermore, the mechanism of tangential force is not clearly explained. In this paper, a special motor stator structure is proposed to explore the effect of tangential force on vibration. First, the analytical calculation of the tangential force and the tangential effect on motor vibration are described. Next, the Theorem of Translation of A Force is introduced to convert the effective tangential tooth force to a radial force couple acting on the stator yoke. Then, a novel motor stator is proposed to investigate the vibration characteristics caused only by tangential force, and the simulation is analyzed. Finally, a vibration test of the prototype is conducted and the result shows the tangential force can induce the radial vibration with corresponding order.

Design, Analysis, and Comparison of Permanent Magnet Claw Pole Motor with Concentrated Winding and Double Stator

Permanent magnet motors have become an important component of industrial production, transportation, and aerospace due to their advantages of high torque density, high power density, high reliability, low losses, and high efficiency. Permanent magnet claw pole motor (PMCPM) is a special type of transverse flux motor which has a higher torque density compared to traditional permanent magnet motors. Due to the absence of winding ends, its axial space utilization is high, and the usage of windings is greatly reduced, reducing the cost and weight of the motor. PMCPM has the advantages of small space, a light weight, a high torque density, a high efficiency, and simple production, which have potential for use in the field of electric vehicles. The double-stator structure design can improve the torque density, efficiency, and radial space utilization of PMCPM, which helps to expand their applications in the field of electric vehicles. This article designs two PMCPM with concentrated winding while different rotor structures (PMCPM1 and PMCPM2) and a three-dimensional finite element method is employed to compare and analyze the performance of PMCPM1 and PMCPM2 and the traditional PMCPM (TPMCPM). Multiphysics analysis is carried out for PMCPM1 and PMCPM2. The stress of the inner and outer stators during interference assembly are analyzed. In this paper, a hybrid material core design is proposed, in which the stator yoke is rolled by silicon steel material and the stator claw pole is pressed by the SMC die method. The multiphysics simulation performance of the PMCPM1 and PMCPM2 with hybrid cores is analyzed.

Electromagnetic-Thermal Analysis of a Hybrid-Excited Flux Switching Permanent Magnet Generator for Wind Turbine Application

An accurate thermal analysis needs to be performed on the machines with new structures to ensure that their electromagnetic performance is not negatively affected. In this regard, this paper details an investigation into the electromagnetic-thermal analysis of an outer rotor hybrid-excited flux switching permanent magnet generator that gains from ferrite PMs in stator yoke and neodymium PMs in rotor segments. Incorporating ferrite PMs and barriers in the stator core enhances the power density of the proposed generator compared to the basic topology. Also, the temperature of the stator and windings of the HEFSG decreases due to the presence of barriers. As a result, the HEFSG can be a potential candidate for DDWT applications. In this study, the thermal modeling started with a 3-D FEM electromagnetic analysis to calculate the losses as heat sources. Afterward, an accurate thermal network was plotted to elucidate the thermal behaviors between various parts of the generator, where the heat sources, heat transfer coefficients, thermal resistances, and heat capacitances form the thermal characteristics of the network, which was then followed by the 3-D FEM thermal analysis. Finally, the experimental test results from the prototyped generator confirmed the accuracy of the simulation results.

Lumped parameter thermal model for segmental translator linear switched reluctance motor

AbstractThe segmental translator linear switched reluctance motor (STLSRM) is a special type of linear switched reluctance motor (LSRM) that has more output power than its conventional type. Therefore, it can be a good choice for certain applications. Heat is one of the factors limiting the output in machines. Therefore, predicting the thermal distribution of machine is as important as the magnetic design. A comprehensive thermal model is presented based on the lumped parameter approach for STLSRM, which predicts temperature distribution in different parts of this motor, including slot winding, end‐winding, stator pole, stator yoke, and the moving part. Considering that the proposed thermal model depends on dimensions and materials used in machine, it can be used for other designs of the STLSRM. The presented thermal model is applied to a typical STLSRM and temperature is determined in its different parts. The simulation results are then compared with the results of 3‐D thermal modelling based on the finite element method (FEM) for validation.

Identification and Analysis of Noise Sources of Permanent Magnet Synchronous Traction Motor with Interior Permanent Magnet

The rapid development of electromobility is placing ever higher demands on new electric motor designs. This results in a gradual reduction in weight with a simultaneous increase in maximum torque. As a result, unfavorable phenomena, such as vibration and noise, can become apparent in the drivetrain. Modeling and evaluation of the acoustic noise sources of a traction motor are particularly important when it is used, for example, as the traction drive of an electric bus, where too high noise levels can have a negative impact on passengers. This article describes methods for analyzing and evaluating the root causes of noise that occurs in permanent magnet traction motors with a rotor in which the magnets have been placed inside the rotor (PMSM IPM). This paper presents an analysis of acoustic noise and forces acting in the air gap of a 240 kW motor with 60 stator slots and 2p = 10 (s60p20) as the number of pole pairs designed for bus and truck drives. To determine the dominant noise sources and evaluate their value, the forces acting in the air gap and their effect on the deflection of the outer surface of the stator yoke were calculated. The natural frequencies of the machine, their frequencies for the entire rotor speed range, and the frequency of vibration of the motor stator were calculated. Based on these data, the sound power level (A-SWL) was calculated at varying motor speeds. MANATEE software (EOMYS, 9, avenue de la Créativité, 59650 Villeneuve d’Ascq—FRANCE) from EOMYS was used to perform vibroacoustic calculations. The analysis results were also subjected to verification on a laboratory bench.

Performance Optimization of Ultralow-Frequency Electromagnetic Energy Harvester Driven by Eccentric mass

Driven by an eccentric mass through a two-layered cantilevered plectrum, the electromagnetic energy harvester (EEH) can convert low-frequency mechanical vibrations into continuous uni-directional rotation. To optimize the performance of the EEH, electromagnetic analysis of the EEH was conducted. Three-phase winding permanent magnet (PM) topology was employed, and combinations of different coils and magnet pole numbers were designed. Then, the finite element method (FEM) was applied to analyze the influence of the combinations of the coils and pole numbers as well as the PM dimensions on the three-phase induced voltage. Prototypes with different configurations were fabricated and the analysis effectiveness was confirmed. Furthermore, different types of stator yokes were designed to enhance the magnetic field. Compared to the original prototype, the output voltage of the optimal prototype increased by 0.5 V with the same rotation speed, and the harmonic components were sufficiently low. Then, experiments with excitation by linear reciprocating motions and swing motions were conducted. Under different exciting conditions, the optimal prototype can also induce the highest voltage amplitude. With an increase in the weight of the eccentric mass, a long duration can be reached that lasts up to 12 s. In summary, the proposed optimization can achieve a high-efficiency and high-power density EEH.

Analytical Calculation Method of Motor Natural Frequencies Based on Equivalent Model of Three-Layer Cylindrical Shell

Accurate calculation of natural frequencies is significant for accurate prediction and suppression of motor vibration and noise. In order to reduce the errors caused by simplified structure in the analytical method, a new analytical calculation method (ACM) of the natural frequencies of the motor is proposed in this paper. The motor enclosure, stator yoke, stator teeth and windings are equivalent to a three-layer cylindrical shell model. The motor feet are equivalent to the axial ribs on the cylindrical shell. The artificial springs are used to simulate arbitrarily complex boundary conditions between the end covers and the enclosure. The combination of zig-zag theory and first-order shear deformation theory (FSDT) is used to calculate the natural frequencies of the equivalent model of the motor proposed in this paper. According to the zig-zag theory model, the respective displacement function and energy equation are established for each cylindrical shell. The different structural dimensions and material properties between the motor enclosure, stator core and windings are considered. The first-order shear deformation theory is adopted in the displacement model of each layer of cylindrical shell, which considers transverse shear deformation, rotational inertia and orthotropy of materials. Finally, the accuracy of the analytical calculation method proposed in this paper is verified by finite element simulation (FES) and hammering method modal test (HMMT).

Contribution to Improve Magnetic Performance and Torque Ripple Reduction of the Low-Speed DSPM Machine

This article deals with the performance improvement of a toothed pole variable reluctance machine excited by permanent magnets housed in the stator yoke. The objective was to reduce the electromagnetic torque ripples caused by the structure geometry and by the supply technique. The machine was designed to meet the specifications of a small wind energy conversion system. The proposed solution improved the electromagnetic design of the new structure in order to minimize the variation of the reluctance. This improvement was obtained by action on the geometry of the structure (the location of the permanent magnets), by action on the stator and rotor tooth pitch, and by the application of an indirect control strategy called torque sharing function. The PSO optimization algorithm was applied in the first part for the optimization of the machine’s global parameters to maximize torque density and then, in the second part, for the research of the optimum tooth pitch parameters to minimize torque ripple. Static and dynamic performances were obtained using 2D-FEM and MATLAB/Simulink software. The results reveal that by action on the stator/rotor tooth pitch, the ripple torque was reduced by about 53%, and by approximately 76% with the used command technique.

A Novel Parallel-Excited Dual-PM Reluctance Machine With Enhanced Torque and Efficiency Performance

This paper presents a novel parallel-excited dual-PM reluctance machine (DPM-RM) with enhanced torque and efficiency performance. The key is to build an integrated magnetic field with two sets of PM excitation sources in both stator yoke and slot openings. Two excitation sources produce a parallel magnetic field, which contributes to a superimposed magnetic flux in the airgap, thus leading to strengthened flux variation, improved back-EMF and torque. Additionally, with a special slot&#x002F;pole combination, biased component and even order harmonics in the phase magnetic flux are eliminated to make the phase flux linkage more sinusoidal. In the meantime, self-inductance variation is greatly suppressed with odd order harmonics of self-inductance removed, resulting in suppressed torque ripple. The prototype is manufactured, and experiments are carried out to verify the effectiveness of the machine design.

Quantitative Analysis of Hybrid-Excited Doubly Salient Machine With Subslot Bottom PMs and Its Comparative Study

This paper proposes a doubly salient machine (DSM) with sub-slot bottom PMs to enhance the torque production. The key is that with auxiliary slot-PM excitation, the stator yoke DC saturation can be mitigated to enhance the torque production capability of DC field excitation, meanwhile additional slot-PM flux can be pushed into the airgap, which can build a parallel excitation and generate additional effective torque. Comparing DC-excited DSM and sub-slot bottom PM DSM (SBPM-DSM), the steady torque can be enhanced by 12.8&#x0025; with the use of sub-slot bottom PMs. In this paper, torque separation effects due to DC field excitation and slot-bottom PMs are quantitatively analyzed with frozen permeability method. By using time-stepping finite-element analysis, the electromagnetic performances of two machines are evaluated. Experimental results verify validity of the proposed design.

A novel magnetic circuit and structure for magnetic levitation ruler

The single axis linear displacement measurement system of CMM is composed of grating ruler, servo motor and linear motion mechanism. Although the measuring accuracy of grating ruler is high, the accuracy of servo motor and linear motion mechanism is low. Therefore, the complex structure limits the measurement accuracy of the linear displacement measurement system. This paper introduces a novel linear displacement measurement system named magnetic levitation ruler. According to the working principle of grating ruler and the characteristics of magnetic levitation technology, the magnetic circuit design and structural design of magnetic levitation ruler are completed in this paper. The mover core of the magnetic levitation ruler is in the stable working magnetic field provided by the stator yoke. The horizontal control coil wound on the mover core can obtain more stable ampere force to improve the control accuracy of the mover core displacement. Therefore, the mover core can be moved in step mode, and the length of each step is fixed. Each step is the minimum scale of the magnetic levitation ruler. Therefore, the mover core can implement displacement measurement while moving in a linear motion. This paper analyzes the working principle of levitation, horizontal motion, and displacement measurement of magnetic levitation ruler, and determines the structural materials and parameters of magnetic levitation ruler with the help of finite element analysis software. The simulation results show that the levitation force of the magnetic levitation ruler is proportional to the current passing through the levitation coils, and the thrust of the horizontal control coil is less disturbed by the magnetic field. Compared with the linear displacement measurement system with rotational servo motor or permanent magnet synchronous linear motor as the core, the magnetic levitation ruler has stable magnetic field, strong controllability, high integration, and is easier to achieve high-precision control.

Control of an Outer Rotor Doubly Salient Permanent Magnet Generator for Fixed Pitch kW Range Wind Turbine Using Overspeed Flux Weakening Operations

This paper deals with the analysis of the dynamic performance of a generator with a doubly salient exterior rotor excited by permanent magnets inserted in the stator yoke. The electrical generator works at low speed and is devoted to a wind energy conversion system. Indeed, the studied generator is a robust high-torque machine and can be directly coupled to the turbine blades. It must therefore assure the energy conversion for wind speeds lower or higher than its base speed. In fact, the control technique used in this work covers the two main operating zones: below the base speed and above it. In the first case, the maximum torque per ampere control law is developed; however, when the base speed is reached, the flux decay control law is implemented and, consequently, the system works above the nominal conditions. Fuzzy logic controllers are employed to regulate direct and quadrature machine currents and DC voltage in order to obtain satisfactory regulation performances. The ensemble of the wind turbine and electrical machine with technical control is performed in Matlab/Simulink software. The simulation results obtained show the capability of the machine to operate at variable speeds, ensuring efficient energy conversion under and over the nominal speed.