High-speed Permanent Magnet Synchronous Machine Research Articles

Effect of Multi-Size Magnetic Powder Gradation on Magnetic Properties of Novel Composite Magnetic Materials for HSPMSM

The ordinary high-speed permanent magnet synchronous machines (HSPMSMs) have the problems of high rotor temperature rise. In order to solve these problems, a novel composite rotor HSPMSM (NCR-HSPMSM) is proposed in this article. The novel composite rotor includes a shaft, sintered permanent magnet, novel composite magnetic materials (NCMMs), and carbon fiber sleeve. The NCMMs are composed of magnetic powder, epoxy, and carbon fiber. The rotor eddy current loss is caused by high-frequency harmonics. Utilizing the low conductivity characteristics of NCMMs, the rotor eddy current loss can be effectively reduced. In addition, the magnetic properties of NCMMs are improved by multisize magnetic powder gradation. The proposed sandwich packing model of the novel magnetic materials is used to determine the minimum magnetic powder size ratio. Also, the effect of multisize magnetic powder gradation on magnetic properties of NCMMs is analyzed by particle flow code (PFC) simulation software, and the electromagnetic analysis of NCR-HSPMSM is carried out by the finite-element method (FEM). Finally, the accuracy of the packing model is verified by the experimental results.

Research on Interturn Short-Circuit Characteristic of the High-Speed Permanent-Magnet Machine With Gramme-Ring Windings

The conventional lap-winding high-speed permanent-magnet synchronous machine (HSPMSM) usually has a large interturn short-circuit (ITSC) current, seriously threatening the reliability. This article founds that the SC coil of the gramme-ring-winding HSPMSM is wound around the stator yoke, so the inductance of SC coil is considerable large and thus will cause a great reduction of ITSC current. The types of ITSC faults were first analyzed for a multistrand-gramme-ring-winding HSPMSM, and then, the ITSC characteristics and influencing factors were investigated based on finite-element (FE) method. The distribution of flux density is quite different from normal state, the SC current is far lower than that of the lap-winding HSPMSM, and the inductance of SC coil is fluctuant with rotation of rotor. By theoretical analysis of the inductance, the methods of increasing the height of stator yoke and using high-permeability CoFe alloy were proposed to further reduce the SC current. In addition, decreasing the strands number is beneficial to reduce the SC current density.

Model Inaccuracy Analysis and Compensation of Stationary Frame-Based Deadbeat Predictive Current Control for High-Speed PMSM Drives

Due to explicit modeling of delay effects and fast dynamic response, the recently reported stationary frame-based deadbeat predictive current control (DBPCC) is particularly attractive for high-speed permanent magnet synchronous machine (PMSM) drives. However, its actual control performances would be heavily dependent on model accuracy. Therefore, this article presents an analytical and systematical investigation into the influences of model inaccuracy on the stationary frame-based DBPCC. Steady-state and transient performance degradations under machine parameter mismatches and inverter nonlinearity over the whole speed range have been studied. Importantly, the analyses show that the steady-state control errors will increase greatly under parameter mismatch as the speed rises; while the transient current tracking errors, only caused by inductance mismatch, can be quickly suppressed after two time-steps. To further improve the parameter robustness of the stationary frame-based DBPCC for high-speed drives, this article also proposes a simple but effective method, called adaptive reference correcting current injection (ARCCI). The proposed method can effectively eliminate all the steady-state current errors caused by model inaccuracy. It can be easily implemented and applicable at high speeds with low switching-to-fundamental frequency ratios (SFRs) as well. Both the presented analyses and compensation methods have been validated by extensive simulations and experiments.

A Simplified Space Vector Pulse Width Modulation Algorithm of a High-Speed Permanent Magnet Synchronous Machine Drive for a Flywheel Energy Storage System

A space vector pulse width modulation (SVPWM) algorithm is an important part of the permanent magnet synchronous machine (PMSM) drive to achieve direct current (DC) to alternating current (AC) conversion. The execution of the conventional SVPWM algorithm is a complex process which will limit the sampling frequency of the high-speed PMSM drive. Low sampling frequency will cause high current total harmonic distortion (THD) and eddy current loss. To increase the sampling frequency, this paper proposes a novel simplified SVPWM algorithm. The proposed SVPWM algorithm turns the vector composition problem of the conventional SVPWM algorithm into an optimization problem of the dwell time of the basic vector. The proposed SVPWM algorithm has an optimal vector dwell time (OVDT). The dwell time of the basic vector can be directly calculated by solving the optimization problem. The proposed SVPWM algorithm does not need sector identification compared to the conventional algorithm. The experiments of the proposed SVPWM algorithm are performed in a high-speed PMSM drive of a flywheel energy storage system (FESS). Compared to the conventional SVPWM algorithm, the execution time of the proposed SVPWM algorithm is reduced by 38%. By using the proposed SVPWM algorithm, the sampling frequency can be increased from 33 kHz to 40 kHz. With the higher sampling frequency, the current THD is reduced by 25.6%. The effectiveness of the proposed simplified SVPWM algorithm is verified experimentally.

High-speed PMSM thermal analysis of totally enclosed fan cooled axial ventilation for centrifugal blower application

A temperature rise occurs when an electrical machine is fully loaded. The winding insulations of high-speed permanent magnet synchronous machines (PMSMs) are the most temperature-sensitive components, which can impact the machine’s longevity. Thus, recently, prediction for high-speed PMSM winding temperature has been given more and more attention. Thermal analysis by numerical (computational fluid dynamics (CFD) and finite element method (FEM)) and analytical lumped parameter thermal network (LPTN) methods have been widely used to estimate the temperature of totally enclosed fan cooled axial ventilation system (TEFCAVS) machines. Although numerical methods have more accuracy, their computation wastes time. Therefore, LPTN is being utilized in this paper due to the fastness of its computation. Firstly, estimated losses of high-speed PMSM with TEFCAVS via electromagnetic analysis, including copper, iron, permanent magnet (PM) eddy current, sleeve eddy current, and mechanical, are coupled to the LPTN model, which acts as heat sources for temperature prediction. Moreover, analysis shows that slot windings’ maximum temperature exceeds the winding insulation class with initial cooling configuration. Secondly, in order to mitigate slot winding temperature, the sensitivity study for liner conductivity, air gap’s heat transfer and lamination to housing’s contact is conducted by LPTN to identify which thermal parameter has more influence on mitigating the maximum temperature of the slot winding. Investigation shows that improving an air gap’s heat transfer has more influence than other parameters for mitigating slot winding maximum temperature below its insulation class. Lastly, the machine is designed and tested with the best thermal-sensitive parameters. Then test results for the maximum temperature of the winding are compared with estimated results to ensure the proposed LPTN correctness, and the calibration process confirms LPTN accuracy.

Electromagnetic and Thermal Analysis of 225 kW High-Speed PMSM for Centrifugal Blower Applications

In order to make centrifugal blowers environmentally friendly, machines with a lighter weight and a more compact size are required. Thus, the axial length of the machine needs to be minimized within the diameter limit. However, in the design methodology, losses and thermal study become very significant; thus, losses increase significantly to achieve the desired output power when the volume is excessively reduced. Moreover, due to the machine’s compact size, heat is concentrated rapidly without adequate cooling. It might lead to a temperature rise of the critical part of the machine above the safe limit, such as winding, thereby affecting its lifespan. This study considers the 225 kW high-speed permanent magnet synchronous machine (HSPMSM) with the forced air cooling axial ventilation system (FACAVS) used in centrifugal blower applications. Firstly, four different analytical models (A2–A5) in the electromagnetic analysis are derived by minimizing the initial machine’s (A1) axial length to achieve a lighter weight and more compact size with better electromagnetic performance. The best among analytical models is chosen as the A4 model with a lighter weight and a more compact structure in addition to higher torque density than A1, A2, and A3 models, and higher efficiency than A1, A2, A3, and A5 models by HSPMSM’s, optimal geometric design, and optimal material choice, respectively. Secondly, LPTN is designed to predict the entire analytical model’s thermal behavior in the thermal analysis. Investigation shows that winding temperature rises from the A4 model is maintained below winding insulation by the determined optimal axial ventilation parameters from the sensitivity analysis. Finally, different analytical models are prototyped and tested. The comparisons between predicted electromagnetic performance, winding temperature rise, and test results were carried out, and the results were found to agree with each other consistently.

Deadbeat Predictive Current Control for High-Speed Permanent Magnet Synchronous Machine Drives With Low Switching-To-Fundamental Frequency Ratios

This article analyzes the conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -frame model-based deadbeat predictive current control (DBPCC) methods for high-speed permanent magnet synchronous machine (PMSM) drives with low switching-to-fundamental frequency ratios (SFRs). It shows that the state-of-the-art compensation schemes of control delay and rotor movement effect can improve the control performance but the problem still arises at very high speeds with very low SFRs. Therefore, this article presents a novel DBPCC method for high-speed PMSM drives. The proposed method tracks the machine stator flux vector in the stationary frame to achieve deadbeat control of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis currents. The control delay and rotor movement effect are both precisely considered. Consequently, the control performance and stability of the proposed DBPCC can be guaranteed at high speeds. Extensive simulations and experiments have been performed on a prototype high-speed PMSM drive. The effectiveness of the proposed method and its superiorities against the field-oriented control and the conventional DBPCCs have all been demonstrated.

Comparative Study of Permanent-Magnet Synchronous Machines with Different Rotor Topologies for High-Speed Applications

High-speed permanent-magnet synchronous machines (HSPMSMs) are an attractive option for proton-exchange membrane fuel-cell systems. Various HSPMSMs have been developed in the past few years. However, it is difficult to judge which the best candidate is. In this paper, aimed at driving a fuel cell vehicle air compressor, four permanent-magnet machines with different rotor topologies were designed and are compared in terms of electromagnetic, mechanical, rotor-dynamics, and thermal performance. The main topologies of these HSPMSMs are introduced and explained. Then, the electromagnetic and mechanical performance of these HSPMSMs was obtained by using a finite-element method (FEM). To reduce PM demagnetization risk, the temperature increase distributed on the HSPMSMs was also obtained. Lastly, some important conclusions were obtained.

Magnetic Properties Analysis of Novel Composite Magnetic Materials for HSPMSMs

High-speed permanent magnet synchronous machines (HSPMSMs) are widely utilized in a variety of industrial applications, such as aerospace and flywheels. The key technical problems, that is, the development of HSPMSMs to high power and high speed, are temperature rise and stress concentration of the rotor. In order to solve the key technical problems, novel composite magnetic materials are proposed in this article. Novel composite magnetic materials are composed of magnetic powder, epoxy, and carbon fiber. In this article, the preparation and molding process of novel composite magnetic materials are proposed. Considering the thermal expansion of epoxy, the analytical model on magnetic properties of novel composite magnetic materials is established. The simulation model of novel composite magnetic materials is determined, and the magnetic properties of magnetic materials with the variation of parameters are analyzed. And the rotor stress and eddy current loss of HSPMSMs are analyzed by the finite-element method (FEM). Finally, the accuracy of the analytical model is verified by the experimental results. The theoretical foundation for the popularization and application of novel composite magnetic materials in HSPMSMs is laid.

Establishment the equivalent model and parameter calculation of a new concept of high-speed permanent magnet synchronous machine with hybrid excitation on the stator

In order to solve the problem that the permanent magnet on the rotor of high-speed permanent magnet synchronous machine (PMSM) is easy to be damaged by centrifugal force and easy to be affected by high temperature, which leads to non-reverse demagnetization, a new concept of high-speed permanent magnet synchronous machine with hybrid excitation on the stator (PMSMHES) is introduced in this paper. And its structure and electromagnetic parts are designed. PMSMHES uses a hybrid excitation method, so that the air gap magnetic field of the permanent magnet motor can be adjusted, thereby solving the problem of a narrow constant power range when the motor is running. Secondly, the equivalent magnetoelectric model of PMSMHES is proposed and the calculation method of related parameters is proposed. Finally, the rationality of the equivalent model and the calculation method of each parameter is verified by finite element simulation.

Dynamic-Decoupled Active Damping Control Method for Improving Current Transient Behavior of LCL-Equipped High-Speed PMSMs

In this article, a novel dynamic-decoupled active damping current controller is proposed for an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -equipped high-speed permanent magnet synchronous machine. Compared with the conventional stationary current-control method for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -type system, the proposed method is established in the synchronous rotating frame for improving the current transient performance. When taking the controller into the synchronous coordinate, there are two following challenges: first, the synchronous resonance frequency varying in a wide range because of the synchronous coordinate transformation, and second, eliminating the coupling between the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${dq}$</tex-math></inline-formula> coordinate. To address these issues, an improved synchronous capacitor-current-feedback active damping method is designed based on arbitrary pole assignment and is significantly effective for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> resonance within the Nyquist frequency. Moreover, a novel dynamic-decoupled motor-current controller is proposed to eliminate the coupling between the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${dq}$</tex-math></inline-formula> -axis motor current. The gain selection method is discussed to acquire sufficient phase margin and gain margin. Finally, the effectiveness of the proposed method is verified by driving the tested motor to 72 kr/min.

Magnetic Performance Improvement Caused by Tensile Stress in Equivalent Iron Core Fabricated by High-Strength Non-Oriented Electrical Steel

This article presents the application of high-strength non-grain-oriented (NGO) silicon steel in the design of the rotor topology of a high-speed interior permanent magnet synchronous machine (IPMSM). By narrowing the magnetic bridges and center posts in the rotor, the purpose of reducing leakage flux and increasing output torque is achieved. Narrower magnetic bridge will cause electromagnetic loss concentration and tensile stress concentration, and tensile stress can effectively weaken the core loss at the part where the iron loss is concentrated. The high-strength NGO silicon steel used in this article is SW35YS600. This high-strength NGO adopts the method of increasing dislocations density to achieve the goal of increasing the structural strength while taking into account the electromagnetic properties at the same time. The electromagnetic properties of this high-strength NGO are less sensitive to tensile stress. As the frequency increases, the improvement of tensile stress on iron loss increases. However, after this material undergoes stress relief annealing, its electromagnetic and mechanical properties deteriorate significantly. Observing the grain structure, it was found that the grains of the high-strength NGO increased significantly after annealing.

Mechanical Parametric Sensitivity Analysis of High-Speed Permanent Magnet Synchronous Machine

The mechanical optimization is critical for the high-speed permanent magnet synchronous machine (HSPMSM) due to its high-speed operating condition. The sensitivity analysis is necessary to improve mechanical strength and stiffness since various influencing factors. This paper presents a mechanical multiobjective optimal design of HSPMSM based on parametric sensitivity analysis. The parameters with marked influence on the rotor stress and critical speed are selected as the design variables: including the material properties, length-diameter ratio, interference size, and bearing stiffness. The parametric sensitivity analysis is performed to provide the influencing magnitude and trend of each parameter. And the best combination of variable levels could be determined. The result shows the performance of the optimized design is improved greatly, which verifies the validity of the proposed optimization method. The sensitivity analysis of each influencing parameter provides guidance for HSPMSM efficient optimization.

A full‐domain fluidic‐thermal approach for a high‐speed PMSM considering the bearing components

This paper presents a refined full-domain model for the fluidic-thermal coupled analyses of a 15-kW 30,000-rpm high-speed permanent magnet synchronous machine (HS-PMSM) considering the heat generation and dissipation of the bearing components. In order to analyse the heat dissipation capacities of the bearing components, firstly, the fluid flow conditions inside the bearings with different revolution and rotation ratios are researched, and the most serious case is taken in the full-domain calculations. Secondly, the three-dimensional (3D) full-domain model is established, and the fluidic-thermal analyses are conducted based on the basic principles of numerical heat transfer and CFD. During calculations, in order to obtain the temperature rise precisely, the angular contact ball bearings are well modelled with all the internal components including the oil films, and the frictional loss in the bearings are computed by the Palmgren model. A 15-kW 30,000-rpm HS-PMSM prototype is established and tested to verify the full domain thermal modelling methodologies and indirectly validate the bearing performance calculations. Finally, a self-ventilated structure is employed to prevent the bearing temperature rise, and the cooling effectiveness is validated by numerical calculations.

Mechanical Analysis With Thermal Effects for High-Speed Permanent-Magnet Synchronous Machines

The high-speed permanent-magnet synchronous machine (HSPMSM) has stricter mechanical restrictions and more intense interactions between multiphysical fields due to high-speed and high-power density characteristics. This article focuses on the thermal effect on mechanical strength and stiffness. As the change of material properties with temperature and the thermal stress caused by thermal expansion properties, this article presents the relationship of the stress and critical speed with two thermal effects obtained by analytical equations and verified by finite-element analysis. The results show that thermal effects could reduce the safety factors of the stress and critical speed, thus increasing the possibility of rotor damage and resonance. To achieve more accurate mechanical, a reasonable machine design is proposed, focusing on the influence of actual uneven thermal distribution. Comparing with a traditional design approach, the new one is more applicable for the HSPMSM design, which considers the assembly method and the operation condition, especially the thermal effects. The fluid-thermal-stress-mode coupling calculation is realized. The experiment has been implemented to verify the validity of this design process. The studies of the thermal effects on mechanical characteristics offer a new idea for designing and debugging practical machines.

Evaluation and loss estimation of a high-speed permanent magnet synchronous machine with hairpin windings for high-volume fuel cell applications

High-speed machines offer several advantages, such as small sizes, avoidance of mechanical gears, and low maintenance, which has led to considerable research dedicated to them in the past decade. In recent times, rectangular wire windings with a hairpin structure have gained prominence in traction motors in the electromobility sector due to their high slot fill factor, simple production, and good thermal properties. Taking these advantages into consideration, this paper analyzes the possibility of using a high-speed permanent magnet synchronous machine (PMSM) with hairpin windings as an electric turbo compressor in fuel cell applications and outlines the critical design aspects.

Design and Optimization of a High-Speed Permanent Magnet Synchronous Machine for Gas Compressors

In this article, a high-speed permanent magnet synchronous machine (PMSM), which is rated at 15 kW and 120 krpm for a gas compressor, is designed and optimized. According to the design specifications, two design schemes of different rotor topologies are presented and compared by the finite element method (FEM) to determine the preliminary scheme of the original machine. The performance of the original machine is obtained by FEM. Meanwhile, the losses of the original machine are analyzed and calculated for optimization. Especially, the conductor diameter of the winding is selected to reduce the copper loss of the machine. Finally, in order to reduce wind friction loss and increase power density, the dimensions of the stator core and the thickness of the permanent magnet (PM) are optimized. Compared with the original model, the wind friction loss is reduced by 17.2%, and the power density is increased by 6.64% in the optimized machine.

Loss and Thermal Analysis for High-Speed Amorphous Metal PMSMs Using 3-D Electromagnetic-thermal Bi-Directional Coupling

To research the impact of temperature-dependent characteristics of windings and magnets on the electromagnetic power loss and thermal properties of high-speed (HS) interior permanent magnet synchronous machines (PMSMs), an electromagnetic-thermal bi-directional coupling method (BDCM) is proposed for water-cooled HS PMSMs considering the assembling gaps between the motor components in this paper. The electromagnetic power loss is calculated by 3-D transient finite-element method and loaded into the 3-D temperature field according to the actual loss distribution, and the materials’ properties are in turn updated according to the temperature distributions. The loss and temperature calculation results of a 15kW HS amorphous metal PMSM are calculated by two different coupling methods in the conditions of the rated-load sinusoidal supply and converter supply, and compared with the measured results in the case of converter supply. The results obtained by the BDCM are more consistent with the experiment results, verifying the superiority of the proposed analyzing method in improving the calculation accuracy of motor loss and temperature rise. In addition, the applicable conditions of the proposed method are also summarized in the paper.

Design of high-speed permanent magnet synchronous machines considering thermal demagnetization and mechanical characteristic of permanent magnet

This paper presents the design for a high-speed permanent magnet synchronous machine (PMSMs) considering the demagnetization and mechanical characteristics of rare-earth magnets based on the operating temperature. The TRV equation and plane stress analytical method are considered for the temperature, the rotor size is derived from the analysis results of the sleeve thickness, and the stator is designed on the basis of the results of the electromagnetic analysis method. The B–H curve of the permanent magnet (PM) changes with its operating temperature; thus, a thermal demagnetization analysis is conducted to verify the irreversible demagnetization caused by the operating temperature and armature reaction field using electromagnetic finite element method (FEM). It is necessary to consider the irreversible demagnetization with the operating temperature because it can decrease the electromagnetic performance. Therefore, the electromagnetic characteristics of high-speed machines using rare-earth PMs are analyzed to confirm irreversible demagnetization. The validity of the proposed design is confirmed via comparative verifications with the measured results from prototype models.

Compensation Method of Position Estimation Error for High-Speed Surface-Mounted PMSM Drives Based on Robust Inductance Estimation

This article proposes a compensation method of position estimation error for high-speed surface-mounted permanent magnet synchronous motors based on robust inductance estimation. The proposed method relies on the variation of the estimated $\delta$ -axis back back-electromotive force when a small current is injected into the $\gamma$ axis. The inductance estimation error is limited within ${\bf \pm \!5\%}$ when the nominal resistance and inductance vary $\bf \pm 30\%$ of their real values. With the estimated inductance, the position estimation error can be well compensated. Compared with the conventional current-injection method, the proposed method has enhanced robustness against the system noises. Benefiting from this, it is effective to estimate the inductance with a small injected current ( $ \bf 0.5\%$ of the rated current), where the conventional methods fail. Finally, the effectiveness of the proposed method is validated by simulation and experiment results on a 100 kr/min (1.67 kHz) high-speed permanent magnet synchronous machines accurately with 10-kHz sampling frequency.