Rotor Structure Research Articles

Design and analysis of a new improved rotor structure in line-start synchronous reluctance motors

Design and analysis of a new improved rotor structure in line-start synchronous reluctance motors

Analysis of the Magneto-Thermal Bidirectional Coupling Strength of Macro and Micro Integration for Self-Starting Permanent Magnet Hysteresis Synchronous Motors

High-speed permanent magnet synchronous motors (PMSMs) are usually started with the hybrid low-speed open-loop and high-speed closed-loop control mode. However, low-speed open-loop control produces large starting current, or even current overload, resulting in demagnetization and motor damage. Therefore, there is an urgent need to develop a high-speed permanent magnet synchronous motor with self-starting ability at low speed, that is, a permanent magnet hysteresis motor (PMHM). This paper takes the permanent magnet ring hysteresis column rotor structure as the research object. Firstly, the performance of this type of rotor is improved using the micro level of effective layer material AlNiCo, and the mechanical properties of AlNiCo are calculated. Secondly, based on the thick-walled cylinder theory, the analytical model for calculating the strength of the composite rotor considering the temperature effect is deduced, and the tangential and radial stress distribution for each part of the rotor under no-load and load conditions are obtained. Then, the electromagnetic losses and temperature field distribution of the rotor are obtained using the magneto-thermal bidirectional coupling finite element method. Finally, strength of the thermal rotor is analyzed by substituting the temperature rise curve function and AlNiCo parameters at the operating temperature. The comparison of the stress calculation results of the semi-analytical solution and the finite element method showed that the error between both of them is less than 5%, which verified that the semi-analytical solution can accurately analyze the thermal stress distribution of the rotor during high-speed rotation.

Study on classifying particle size and spatial internal flow field of T-shaped tooth structure in a disturbing rotary centrifugal air classifier

In the present study, three perturbed rotor structures were designed to investigate the performance of a new perturbed rotary centrifugal airflow classifier through experiments and numerical simulations. A model for the maximum and minimum classification particle size was established on the basis of the mechanical analysis of the blade. Pressure distribution and flow patterns at different positions in the Z-X and Z-Y planes of three structures under different rotational frequencies were analyzed, as well as the classification performance. The results show that in the rotor with different tooth structures operating at a critical rotational frequency, the internal flow field have abnormal pressure distribution, where the smaller density and velocity of the gas–solid phase reduce particle motion velocity, centrifugal force, and collision opportunities, forming particle sidewalls near the screen surface, thereby deteriorating the classification effect. The classification performance of the three structures under different operating parameters shows that when the rotation frequency exceeds 24 Hz, feed rate is 0.3 kg/s, and classifier inclination angle is −4°, the highest macroscopic and microscopic classification efficiency of the single-row tooth structure is 94.21% and 94.23%, respectively. The study can provide a reference to improve the flow field and classification performance of air classifiers in industrial applications.

Design and analysis of PM‐assisted synchronous reluctance machine with shifted magnetic poles

AbstractThe authors present a new design of a PM‐assisted synchronous reluctance motor (PM‐SynRM) with uneven air‐gap length to improve the power factor and enhance the torque production capability. The rotor structure is modified to properly shift rotor magnetic poles and therefore (i) increases the back‐EMF and the electromagnetic torque, (ii) allows electromagnetic torque and reluctance torque components peak near the same current phase angle. The proposed solution is simple, does not require changing the arrangement of magnets and/or flux barriers and is applicable to all types of PM‐SynRMs. Sensitivity analysis is carried out to determine the extent of which the proposed magnetic pole shifting may impact the resultant torque profile. To assess the level of success, the electromagnetic characteristics of the proposed design (e.g. torque, power factor, and back‐EMF) are compared against the baseline structure under the same operating conditions. For verification purposes, Finite Element simulation results are validated via a series of analytical calculations and experimental measurements, and supported with detailed theoretical discussion.

Sphericity measurement based on telecentric imaging mechanism with image distortion correction and eccentricity error compensation

Sphericity is an essential geometric parameter for determining the processing manufacturing quality of spherical components. This study presents a sphericity measurement method based on telecentric imaging mechanism with image distortion correction and eccentricity error compensation. A sphericity measurement system is designed, and the projection images of the cross-section on the equatorial plane of the measured sphere are acquired using a line scan camera with bilateral telecentric lenses. An analytical camera model for this sphericity measurement system is established by considering major sources of image distortion. The subpixel edge points of the projection images are extracted and converted to cross-sectional profiles on the equatorial plane according to the camera model. An eccentricity error compensation strategy for contour matching of the obtained cross-sectional profile on the equatorial plane is also developed to obtain the three-dimensional contour point coordinates of the sphere. Sphericity is then calculated according to the least square criterion. The effectiveness of the proposed method is verified by measuring two steel balls with diameter in 20 mm and 30 mm. The sphericity measurement error is reduced by 0.3383 mm and 0.4653 mm respectively after image distortion correction and is reduced by 0.2268 mm and 0.0795 mm respectively after eccentricity error compensation. The proposed method can be extended to form error measurements for opaque components with rotary structure on the outer contour.

Comparative Analysis of Consequent-Pole Flux-Switching Machines with Different Permanent Magnet Arrangements for Outer-Rotor In-Wheel Direct-Drive Applications

Recently, the interest in consequent-pole flux-switching permanent magnet (CP-FSPM) machines has been increasing because of the flux-focusing PM arrangements and the removal of the flux-barrier effect. A simple and rigid outer-rotor salient pole rotor structure can be adopted in CP-FSPM machines, making them applicable for in-wheel direct-drive applications. In this study, three CP-FSPM machines with II-shaped (II-PM), V-shaped (V-PM), and straight U-shaped PM (SU-PM) arrays are analyzed and compared. Moreover, a CP-FSPM machine with inclined U-shaped PM (IU-PM) arrays is proposed to improve the flux-focusing effect and stator slot utilization. The working principles of CP-FSPM machines are analyzed by adopting a semi-analytical model. Combining the finite element analysis (FEA) results of air gap flux density and the analytical model of phase back electromotive force (EMF), the contributions of multiple working harmonics to the back EMF are quantitatively analyzed. Additionally, 6/16 and 6/17 CP-FSPM machines with different PM arrangements are globally optimized. Both the no-load and on-load performance of the optimized machines are included in the performance comparison. The results illustrate that the 6/16 and 6/17 machines exhibit their respective merits, and the IU-PM machine shows the best torque production ability in these CP-FSPM machines with the same design criteria.

Optimal design of rotor structure for vibration and noise reduction in electric vehicle generator

In order to reduce the vibration noise of an extended-range electric vehicle (EREV) generator, an optimization method based on changing the rotor structure is proposed in this paper. Firstly, the specific optimization scheme is determined by theoretical and simulation analysis to perform skew pole segmentation of the rotor, while using an eccentric pole arc design to determine the optimal parameters with the target of cogging torque. Then, in order to verify the feasibility of the scheme, the main performance of the generator before and after the optimization is analyzed, including radial electromagnetic force wave, counter-electromotive force (counter EMF), electromagnetic torque, and rotor strength. Finally, a high-precision finite element model of the generator was established, the vibration acceleration, as well as the sound pressure level before and after optimization, were calculated, and a noise test was completed. The results show that the optimized scheme significantly weakened the cogging torque of the generator, while reducing the radial electromagnetic force wave and counter EMF distortion rate to a certain extent, and finally significantly improved the vibration and noise performance of the generator.

Influence of the number of front and rear rotor blades on the hydrodynamic performance of counter-rotating horizontal-axis tidal turbines

The coaxial rotor structure presents significant potential for the development of tidal turbines. In order to study the effect of the number of front and rear rotor blades on the hydrodynamic performance of counter-rotating horizontal-axis tidal turbines (CRHATTs), three models (CRHATT 3-2, CRHATT 3-3 and CRHATT 3–4) are established at the same tip speed ratio (TSR), and the accuracy of the numerical method is verified by experiments. The effect of blade number on the performance coefficients, velocity and pressure pulsations and vortex structure of CRHATTs are calculated based on CFD method and spectral analysis. The results show that the relationship of the power coefficient for the three models is: CRHATT 3–4 > CRHATT 3-3 > CRHATT 3-2. The turbulent kinetic energy in the flow field can be transferred more quickly from the large-scale vortex structure to the small-scale as the number of rear rotor blades increases. By weighing aspects such as load fluctuation and power coefficient, the CRHATT 3–4 can produce the largest power coefficients, the best stability during operation and the least vibration on the blades among the three models. This paper provides significant guidance for the engineering design and optimization research of CRHATTs.

Analysis of performance and flow structures of cycloidal rotors under different pitch-pivot-point and blade camber conditions

The performance and unsteady vortical flows of a 2-bladed cycloidal propeller are investigated using the SST γ−Re‾θt transition model, under different pitch-pivot-point and blade camber conditions. Firstly, it shows that the results of the present computations match well with the previous numerical data and experiments, in terms of the instantaneous performance and internal flow structures. Then, due to the moderate propulsive force and low power, the cycloidal rotor with a pitch-pivot-point of x/c = 0.25 maximize the efficiency. Moving the pitching location to the leading edge increases the lift and leads to the earlier flow separation on the blade surface. However, as the pitch-pivot-point shifts to the middle chord, the power of the cycloidal rotor increases dramatically because of the massive flow separation, leading to the degradation of the performance. Simultaneously, the symmetrical profiles, involving NACA0012 and 0015, are recommended due to the wide operation condition with high efficiency. The thick symmetrical and asymmetrical airfoils produce the worst performance due to the large power that is consumed. Furthermore, owing to the change of the rotating speed only, the advance coefficient effect is more obvious than the Reynolds number. When analyzing the performance of the rotating system at any position, one should consider the performance, pressure difference, near-wall flows and forces (lift and drag) of each blade.

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.

Capturing Energy From Power Transmission Lines Galloping and Self-Powered Sensing of Galloping State Through a Rotary Structural Electromagnetic Energy Harvester

This paper was characterized of capturing vibration energy from transmission lines galloping based on electromagnetic generator (EMG) and the joint utilization thereof to assessment of galloping state. An EMG based on the rotary structure of stator and rotor was proposed oriented to the structural features of transmission lines, and the design parameters were optimized to enhance the output through finite element simulation. The output performance of EMG was conducted on the linear motor testing platform, the output of EMG under the conductor galloping conditions reached 0.16 to 3.01 V and 0.96 to 14.46 mA, respectively, the maximum power of EMG through power management circuit reached 0.12 to 12.81 mW from the vibration frequency of 0.5 to 2.5 Hz. The feasibility of EMG was well validated on the conductor galloping testing platform, the maximum power through power management circuit reached 1.47 to 13.51 mW from the vibration frequency of 0.7 to 2.8 Hz, and the conductor galloping state can be preliminarily judged according to the proposed peak value analysis, validating that the proposed EMG has great potential application for energy harvesting of conductor galloping for low-power electronic appliances and the evaluation of conductor galloping state.

Fast Magnetic Field Prediction Based on Hybrid Subdomain Method and Multiobjective Optimization Design for Interior Permanent Magnet Synchronous Machines

Benefiting from the prosperity of new energy industry, interior permanent magnet synchronous machines (IPMSM) have ushered in unprecedented development opportunities. To further suppress defects and enhance engineering practicality, fast magnetic field prediction based on hybrid subdomain method and multiobjective optimization design for IPMSM are studied. First, fast no-load magnetic field prediction model based on hybrid subdomain method for IPMSM is innovatively proposed. By combining master/slave subdomain division method and lumped parameter magnetic equivalent circuit, complex rotor structure and saturation effects of magnetic bridges and cores can be comprehensively considered. Prediction model has extremely high calculation accuracy and speed. After that, based on the proposed prediction model, a multiobjective optimization model combining Taguchi method and nondominated sorting genetic algorithm II (NSGA-II) is implemented. Model optimization efficiency has been greatly improved scientifically and effectively. Finally, the efficiency, advancement, innovation, and engineering practicability of studied prediction and optimization models are well verified through a series of finite element analysis (FEA) and prototype experiments. In addition, the generality and universality of this study are verified for other types of IPMSM.

Improvement Undesirable Characteristics of the Switched Reluctance Motor With Triangular Rotor Structure

The conventional switched reluctance motors (CSRMs) confront two key challenges, including torque ripple (TR) and radial force (RF), which are the foundations of creating noise, vibration, and tension that limits the applications of the motor. In order to reduce inappropriate inherent effects of the CSRMs, optimizing via motor structure will be more comfortable and less costly than control methods. Due to its simplicity and being without coils in the rotor, this part will be a suitable candidate for improvement destinations. In this paper, a novel structure of the rotor is presented in order to reduce the TR and RF of this motor. The proposed structure is derived from the conventional one with a triangular shape in the middle of rotor, known as a Triangular Rotor Switched Reluctance Motor (TRSRM). Finding the best geometric of the proposed model fulfilled by sensitivity analysis (SA) alongside 3-D finite element analysis (3D-FEA) and the best configuration for comparison to the CSRM selected. Experimental and simulation results demonstrate that TRSRM diminishes RF and TR compared to the CRSRM while keeping the weight and volume fixed and also has a low cost and simple manufacturing. These features make the proposed structure suitable for continuous-operation applications such as air blowers in industrial devices.

Influence of Rotor Damping Bars on Rotor Temperature Rise of Synchronous Condenser After Single-Phase Short-Circuit Fault

A synchronous condenser (SC) can provide the transient reactive power support for the Ultra High Voltage Direct Current (UHVDC) converter station. However, the rotor temperature rise is generally the main factor which limits the transient operation ability of the SC. In this paper, a rotor structure of the SC with the rotor damping bars made of different materials in the rotor large teeth is proposed to reduce the rotor temperature rise. In order to obtain the influence of the rotor damping bars on the temperature rise, the rotor loss and temperature distribution of a 300-MVar SC under the single-phase short-circuit fault are calculated by coupling the electromagnetic field, loss and temperature field models of the SC with the model of the power grid. For the damping bars made of the copper, aluminum and stainless steel, the rotor maximum temperature rises are calculated and compared. According to the maximum permissible temperature of the rotor core, the transient operating ability of the SC with the rotor damping bars made of different materials is obtained under the single-phase short-circuit fault. This study can provide the theoretic basis for the improvement of the transient reactive power support capacity of the SC under the single-phase short-circuit fault.

Towards an Integrated Design of Direct-Drive Wind Turbine Electrical Generator Supporting Structures

Rotor and stator support structures of significant size and mass are required to withstand the considerable loads that direct-drive wind turbine electrical generators face to maintain an air-gap clearance that is open and stable. With the increase of scale, reducing the weight and environmental impact of these support structures is believed to be one of the key components to unlocking the true potential of direct-drive generators. An investigation on the electrical generator rotor structure of the IEA 15 MW offshore reference wind turbine was conducted. An integrated approach that considered the environmental impact, including the manufacturing energy usage and CO2 footprint, as well as the financial repercussions of structural parameter modifications as they are optimised was followed, making use of distinct commercial pieces of software. The rotor structure was parametrically optimised, and its operating loading conditions were evaluated at various size scales. The study determined that the effect of thermal loading is significant, which forces the designer to augment the mass to comply with the imposed structural requirements. The ensuing life-cycle assessment showed an increase in the environmental impact due to the consideration of this particular load, whose effect in structural deflection and stress has been typically underestimated.

Rotor dynamics informed deep learning for detection, identification, and localization of shaft crack and unbalance defects

This paper proposes a new model, called rotor finite element mimetic neural network (RFEMNN), for diagnosing rotor unbalance and shaft crack faults. RFEMNN uses a convolution long short-term memory networks (CNN-LSTM) architecture to achieve fault recognition and localization in the rotor structure. The term “Mimetic” refers to the topology of the rotor finite element model and solution process by custom designing NN structure and data flow, which is based on the physics informed structure paradigm. The proposed “Mimetic” theory enhances the physics consistency of the RFEMNN model without requiring complete analytic physical knowledge or all parameter values. The proposed model’s effectiveness is validated through experimental tests, compared to 9 benchmark models from the literature and one deep learning model with the same depth but no physics embedding. Results showed that RFEMNN outperformed the benchmark models with a comprehensive diagnostics accuracy of 94.7%, indicating its potential for practical industrial applications.

Coupled free vibration analysis of rotating non-uniform cantilever beams by an element-wise Ritz method using local hierarchical functions

The coupled free vibration behaviour of rotating non-uniform cantilever beams is investigated by an efficient and accurate element-wise Ritz method using Bardell’s polynomials as local hierarchical functions. Both bending-twisting and bending-extension coupling is included in the beam model. The same hierarchical set can be suitably modified to satisfy the essential boundary conditions and represent the stretching, bending and rotation of the beam. The global matrices are obtained by minimizing the Lagrangian functional. The inter-element compatibility conditions are satisfied, and a condensation procedure is used to obtain the condensed matrices for the eigenvalue problem. The procedure is validated with examples from published studies and various case studies are presented to demonstrate the accuracy and convergence of the proposed method. A parametric study is presented to show the effect of various parameters on the free vibration response of rotating non-uniform beams. The frequency veering phenomenon is observed during the study. The proposed approach provides a simple and efficient approach for analyzing the free vibrations of rotating structures such as wind turbine rotor blades, helicopter blades, propellers, and structures with strong discontinuities, especially in the preliminary design stage.

Application of an Improved Ridgelet Process Neural Network for Predicting the Temperature Rise of Rotor Structure Optimization

To solve the negative-sequence temperature-rise problem of large equipment under asymmetric operating conditions, this paper optimizes the structure of the main components and adopts an improved process neural network to conduct online analysis and calculate the operating data, achieving the accurate prediction of the equipment heating status. Firstly, taking a 300 MW generator that urgently needs equipment improvement as the research object, the typical asymmetric accident characteristics that have occurred in recent years and the main influencing factors of negative-sequence heating of the rotor are analyzed. The influence of the rotor damping structure and shaft length on the temperature-rise change is explored. Secondly, a tent map is introduced to enhance the distribution uniformity of the population in the search space to enhance the global convergence of niche genetic algorithms. Numerical experiments and field experiments show that the improved algorithm, which is applied to optimize the parameters of the ridgelet process neural network, has good temperature-rise prediction performance. Finally, the influence of the rotor length and number of pole damping bars on the negative-sequence heating problem under different negative-sequence component ratios is examined, which provides useful references for the structural optimization and asymmetric operation state prediction of large equipment.

Influence of rotor slot profile on the windage loss in a Switched Reluctance Motor for an electric autorickshaw

A Switched Reluctance Motor is designed for an electric auto rickshaw operating at 25 kmph. Different stator-rotor teeth combinations are worked out and the suitable combination for the application is chosen. As the application demands higher operating speeds (up to 9500 rpm), windage loss tends to hamper the machine's efficiency at these speeds. One parameter that affects the windage loss is the drag force. The drag force contributed by the rotor can be varied by changing the profile of the rotor slot. Hence, certain structural variations in the rotor slot are carried out and Computational Fluid Dynamics (CFD) is used to estimate the windage loss of each rotor slot profile. The rotor structure providing minimal windage loss is chosen for fabrication. Testing is performed on the fabricated motor and the results are compared.

Topology optimization and parameter optimization hybridized by mesh smoothing for IPMSM design

PurposeTopology optimization (TO) methods have shown their unique advantage in the innovative design of electric machines. However, when introducing the TO method to the rotor design of interior permanent magnet (PM) synchronous machines (IPMSMs), the layout parameters of the magnet cannot be synchronously optimized with the topology of the air barrier; the full design potential, thus, cannot be unlocked. The purpose of this paper is to develop a novel method in which the layout parameters PMs and the topology of air barriers can be optimized simultaneously for aiding the innovative design of IPMSMs.Design/methodology/approachThis paper presents a simultaneous TO and parameter optimization (PO) method that is applicable to the innovative design of IPMSMs. In this method, the mesh deformation technique is introduced to make it possible to make a connection between the TO and PO, and the multimodal optimization problem can thereby be solved more efficiently because good topological features are inherited during iterative optimization.FindingsThe numerical results of two case studies show that the proposed method can find better Pareto fronts than the traditional TO method within comparable time-consuming. As the optimal design result, novel rotor structures with better torque profiles and higher reluctance torque are respectively found.Originality/valueA method that can simultaneously optimize the topology and parameter variables for the design of IPMSMs is proposed. The numerical results show that the proposed method is useful and practical for the conceptual and innovative design of IPMSMs because it can automatically explore optimal rotor structures from the full design space without relying on the experience and knowledge of the engineer.