Surface-mounted Permanent Magnet Research Articles

DECREASING TORQUE RIPPLE OF A SLOTLESS PERMANENT MAGNET TORQUE MOTOR USING A DOUBLE-LAYER WINDING

The torque of a magnetoelectric torque motor with surface-mounted permanent magnets on the rotor was studied. The sinusoidal current supply mode is considered. The torque was calculated according to the static model of the magnetic field. It was determined that the sixth harmonic makes a significant contribution to the torque ripple. To reduce the sixth harmonic it is proposed to use a winding with a shortened pitch, for which it is necessary to make this winding in two layers. The optimal values of the number of pole pairs, the angular width of the magnets of the magnetic field exci-tation system, and the shortening of the winding pitch were determined. It was found that shortening of the winding pitch decreases the torque ripple by 2 ... 2.5 times. References 7, figures 6, tables 3.

Analytical Modeling of Steel Shielding Cylinder in Surface-Mounted Permanent Magnet Machines

Two-dimensional (2-D) analytical modeling of permanent magnet machines with shielding cylinder is a challenging task due to the saturation effect of the cylinder. This paper presents a 2-D hybrid analytical solution to model surface-mounted permanent magnet machines with a shielding cylinder attached to the exterior of the rotor body. The presented model provides an accurate representation of the motor response by accounting for the saturation effect of the shielding cylinder, as well as the stator slotting effect. For this purpose, the steel shielding cylinder is modeled by a vacuum cylinder (with the exact same size/dimension) and two inner and outer virtual surface currents. The values of the surface currents are determined by using the respective magnetic circuit model. Meanwhile, the slotting effect on the tangential flux component is modeled by injecting a virtual surface current onto a slotless stator surface. Next, the radial and tangential flux density are obtained by solving Poisson's equation via separation of variables theorem and applying relevant boundary conditions. The accuracy of the proposed model is verified by the finite element and experimental tests on the machine prototype.

A Thorough Procedure to Design Surface-Mounted Permanent Magnet Synchronous Generators

This paper sets forth a thorough procedure to design surface-mounted permanent magnet synchronous generators. Since synchronous generators generate the majority of electrical energy, their relevance in society nowadays is substantial. As a consequence, the methodology to design these electrical machines also holds great importance. However, even though a considerable amount of works addresses the matter, it is difficult to find a complete and thoroughly explained design procedure. The proposed method is based on analytical equations to fully consider PM generator fundamentals with a few simplifications, which implies in a considerable number of design equations and parameters. Differently from most papers on the design of PM synchronous generators, a significant level of detail and explanation is presented, all design choices are discussed, and the suggested ranges for the design parameters are shown. This results in a straightforward procedure that allows non-experienced designers to easily replicate the results and effectively enhance the comprehension of permanent magnet synchronous machines, and provides a guideline for researchers from other fields who may need to understand and perform a synchronous generator design. To show the effectiveness of the proposed design procedure, a PM generator is designed, and the results are compared with a finite element simulation, showing good accuracy.

A Reliable and Efficient I-f Startup Method of Sensorless Ultra-High-Speed SPMSM for Fuel Cell Air Compressors

Extended back electromotive force (EEMF)-based position sensorless field-oriented control (FOC) is widely utilized for ultra-high-speed surface-mounted permanent magnet synchronous motors (UHS-SPMSMs) driven fuel cell air compressors in medium-high speed applications. Unfortunately, the estimated position is imprecise due to too small EEMF under low speed operation. Hence, current-to-frequency (I-f) control is more suitable for startup. Conventional I-f methods rarely achieve the tradeoff between startup acceleration and load capacity, and the transition to sensorless FOC is mostly realized in the constant-speed stage, which is unacceptable for UHS-SPMSM considering the critical requirement of startup time. In this article, a new closed-loop I-f control approach is proposed to achieve fast and efficient startup. The frequency of reference current vector is corrected automatically based on the active power and the real-time motor torque, which contributes to damping effect for startup reliability. Moreover, an amplitude compensator of reference current vector is designed based on the reactive power, ensuring the maximum torque per ampere operation and higher efficiency. Furthermore, the speed PI controller is enhanced by variable bandwidth design for smoother sensorless transition. These theoretical advantages are validated through experiments with a 550 V, 35 kW UHS-SPMSM. The experimental results demonstrated the enhanced startup performance compared with conventional I-f control.

Multiphysics performance of surrogate models on skewed pole surface-mounted permanent magnet motors

Purpose Evaluating the multiphysics performance of an electric motor can be a computationally intensive process, especially where several complex subsystems of the motor are coupled together. For example, evaluating acoustic noise requires the coupling of the electromagnetic, structural and acoustic models of the electric motor. Where skewed poles are considered in the design, the problem becomes a purely three-dimensional (3D) multiphysics problem, which could increase the computational burden astronomically. This study, therefore, aims to introduce surrogate models in the design process to reduce the computational cost associated with solving such 3D-coupled multiphysics problems. Design/methodology/approach The procedure involves using the finite element (FE) method to generate a database of several skewed rotor pole surface-mounted permanent magnet synchronous motors and their corresponding electromagnetic, structural and acoustic performances. Then, a surrogate model is fitted to the data to generate mapping functions that could be used in place of the time-consuming FE simulations. Findings It was established that the surrogate models showed promising results in predicting the multiphysics performance of skewed pole surface-mounted permanent magnet motors. As such, such models could be used to handle the skewing aspects, which has always been a major design challenge due to the scarcity of simulation tools with stepwise skewing capability. Originality/value The main contribution involves the use of surrogate models to replace FE simulations during the design cycle of skewed pole surface-mounted permanent magnet motors without compromising the integrity of the electromagnetic, structural, and acoustic results of the motor.

Design and Analysis of Surface-Mounted Permanent-Magnet Field-Modulation Machine for Achieving High Power Factor

Along with the establishment of general air-gap field modulation theory, a new type of field-modulation machine has attracted increasing attention. However, the low power factor always plagued its popularization. This paper is to focus on the simplest structure surface-mounted permanent-magnet field-modulation (SMPMFM) machine, aiming at exploring the implementation of high power-factor design. The key is that the power factor calculation formula is derived parametrically, hence the originally vague causal relationship between the structural parameters and power factor become clear, guided by which the initial structure design for high power factor achievement is determined, meanwhile the power factor adjustment evaluation and the electromagnetic performance comparison with the help of finite element analysis (FEA) are conducted to verify the validity of the proposed power factor calculation formula. Finally, a feasible high-power-factor SMPMFM prototype is fabricated and the experimental testing is performed, which has a good agreement with the formular calculation and FEA results. Hence, the validity of the proposed analysis for achieving high power-factor design of field-modulation machines is verified.

Design of Fractional-Order Non-Singular Terminal Sliding Mode Observer Sensorless System for Surface-Mounted Permanent Magnet Synchronous Motor

A new sensorless speed control system for a fractional-order terminal non-singular sliding mode surface-mounted permanent magnet synchronous motor is proposed. The fractional terminal non-singular sliding mode surface, which can converge in finite time, is designed by combining the fractional-order control theory with the terminal attractor concept. Then, a new control rate is proposed to reduce system buffeting. Secondly, an adaptive back electromotive force filter is designed to reduce the harmonics in the sliding mode function estimation and improve the observation accuracy. In addition, the theoretical analysis of the designed system proves that the system can converge in a finite time. Then, a fraction-order phase-locked loop with variable factors is designed to make the system more capable of tracking the rotor. Finally, a simulation and experiment platform is built, and a comparison experiment is carried out, which proves that the designed algorithm has a stronger rotor position tracking ability and a better dynamic performance of the system.

FCS-MPC for Three-Level NPC Inverter-Fed SPMSM Drives Without Information of Motor Parameters and DC Capacitor

The conventional finite control set-model predictive control (FCS-MPC) suffers from poor robustness against model mismatches. This paper presents an improved FCS-MPC with a reconstructed mathematical model to predict current variations without using a lookup table (LUT) or motor parameters. The model coefficients and current variations related to different voltage vectors can be updated during each control period. As a result, the prediction error is significantly reduced at low switching frequency when compared with the prior LUT-based model-free predictive current control (MFPCC). Additionally, the tracking accuracy of the proposed method at high speeds is improved due to the elimination of approximation error. Furthermore, a simple scheme is developed to suppress neutral-point-potential drift without knowledge of the dc-bus capacitor. Simulation and experimental tests, along with comparisons with prior arts carried out on a three-level inverter-fed surface-mounted permanent magnet synchronous motor drive, confirm the superiority of the proposed method.

Improved Model Predictive Speed Control of a PMSM via Laguerre Functions

This paper proposes a model predictive speed control strategy for a surface-mounted permanent magnet synchronous motor by applying Laguerre functions. The model predictive controller (MPC) incorporates an integrator. A quadratic programming procedure is applied to solve the constrained optimization problem online. The paper also provides a solution for stability. The performance efficiency of the proposed scheme is validated by comparing the results with the performance of an optimal linear quadratic regulator, conventional state-space model predictive control, and a simple MPC algorithm with integral action. Extensive simulation results confirm the efficacy of the proposed scheme, showing that it achieves good steady-state performance while maintaining a fast dynamic response.

Design and Optimisation of a 5 MW Permanent Magnet Vernier Motor for Podded Ship Propulsion

The evolution of electric propulsion systems in the maritime sector has been influenced significantly by technological advancements in power electronics and machine design. Traditionally, these systems have employed surface-mounted permanent magnet synchronous motors (PMSMs) in podded configurations. However, the advent of permanent magnet Vernier motors (PMVMs), which leverage magnetic gearing effects, presents a novel approach with promising potential. This study conducts a comparative analysis between PMVMs and conventional PMSMs at a power level of 5 MW for podded ship propulsion, with a particular focus on the impact of gear ratios (Gr). An objective function was developed that integrates motor dimension constraints and the power factor (PF), a critical yet frequently neglected parameter in existing research. The findings indicate that PMVMs with lower Gr have lower mass and cost compared to those with higher Gr and traditional PMSMs, at a PF level of 0.7, which is high for Vernier machines. Moreover, PMVMs with lower Gr achieve efficiencies exceeding 99%, outperforming both their higher Gr counterparts and conventional PMSMs. The superior performance of PMVMs is attributed to lower current density and reduced copper loss, which contribute to their enhanced thermal performance. These details are elaborated on further in the paper. Consequently, these findings suggest that PMVMs with lower Gr are particularly well suited for high-power maritime propulsion applications, offering advantages in terms of compactness, efficiency (EF), cost-effectiveness, and thermal performance.

Sensorless Control of Surfaced-Mounted Permanent Magnet Synchronous Motor in a Wide-Speed Range

This paper delves into a comprehensive study of a wide-speed-range sensorless control approach for surface-mounted permanent magnet synchronous motors (SPMSMs). In the low-speed range, a novel high-frequency pulse voltage injection (HFPVI) method is introduced for rotor position estimation, which does not depend on motor saliency and is well-suited for SPMSMs. This method incorporates a second-order generalized integrator (SOGI) and a new modulation signal to enhance the accuracy of rotor position estimation. For medium-to-high speeds, an improved super-twisting sliding mode observer (STSMO) utilizing a continuous hyperbolic tangent function is proposed to mitigate chattering. Additionally, a new phase-locked loop (NPLL) is introduced to accurately obtain the rotor position. Furthermore, this paper designs an exponential weighted switching function to facilitate a smooth transition of the motor from the low-speed domain to the medium- and high-speed domains. The effectiveness and superiority of the proposed methods are validated through simulations and experiments conducted on an RTU-BOX platform. The rotor position estimation errors of the proposed new HFPVI method and the improved STSMO method under various operating conditions are both approximately 0.05 rad (2.8 elc·deg), and the SPMSM can switch smoothly from the low-speed range to the medium- and high-speed ranges.

Analysis and reduction of electromagnetic vibration in integral-slot PM machine by functional magnet structure

It is significant to balances torque and vibration performance for the surface-mounted permanent magnet (PM) machines. This paper proposes a functional magnet structure to suppress the vibration response of integral-slot surface-mounted PM machines. At the same time, the torque ripple is also greatly reduced without sacrificing the average torque. Firstly, taking the 48-slot/8-pole PM machine as an example, the main sources of the air-gap radial force are analyzed based on the Maxwell stress equation. Thereby, the main PM flux density harmonic components that contribute to the radial force are pointed out. Secondly, the design method of different functional magnet structure is investigated. Then, the effects of different magnet shapes on the torque and vibration performances are compared. The result shows that the proposed sinusoidal+3rd-order harmonic injection functional magnet structure can effectively improve the vibration performance without sacrificing the average torque. Finally, the prototype of the 48-slot/8-pole PM with functional magnet structure is manufactured, and the experiments are carried out for validation.

Prediction of Electromagnetic Performance for IPMSM Based on Improved Analytical Model Considering Saturation Effects

Unlike surface-mounted permanent magnet synchronous motors (SPMSM), the rotor structure of interior permanent magnet synchronous motors (IPMSM) is irregular and relatively complex. This makes the analytical calculation for IPMSM quite complicated. Except for the use of some equivalent methods to make irregular permanent magnets (PMs) regular, existing subdomain models often cannot effectively and directly account for the complex rotor structure and cannot be easily applied to IPMSM. For this reason, an improved analytical model applicable to IPMSM is presented, studied, and developed in this article. First, a novel subdomain model division method is innovatively introduced. Complex rotor structure can be well accounted for. This not only facilitates the expression of vector potential and satisfies the establishment of subdomain model, but also recovers the original rotor topology to the maximum extent and effectively avoids many uncertainties and unreliability caused by over-equivalence. Afterwards, the magnetic equivalent circuit and equivalent surface current method are combined to fully consider the saturation effects of magnetic isolation bridges, rotor ribs, and cores. Model analysis accuracy is well guaranteed. Further, the precise subdomain method is investigated to achieve fast prediction of key electromagnetic performance. Both finite element analysis (FEA) and prototype experiment strongly highlight the validity of the improved analytical model. In addition, compared to FEA, the improved analytical model does not require tens of thousands of computation cells, which saves a lot of time and storage while ensuring the same prediction accuracy. This opens up unlimited possibilities for the design and optimization of IPMSM.

Analytical Prediction of D- and Q-Axes Inductance for Dual Three-Phase Surface-Mounted Permanent Magnet Motor Accounting for Eccentric Pole and Tooth Saturation

This paper presents an analytical model to calculate the d- and q-axis Inductance of dual three-phase surface-mounted permanent magnet motor accounting for eccentric pole and tooth saturation. The novel method combines the advantages of the subdomain model and lumped parameter magnetic circuit model. This motor is divided into several subdomains. And the eccentric pole is further subdivided into multiple symmetrical regions. Based on the Poisson’s and Laplace’s equations, the subdomain model is established. The reluctance of the tooth and the tip is calculated by the subdomain model and lumped parameter magnetic circuit model. According to the relationship between the tooth reluctance, tip reluctance and the corresponding air-gap reluctance, the equivalent air-gap magnetic density coefficient is obtained. Based on the coefficient, the new air-gap magnetic density and tooth magnetic density are solved. For the solution of saturation, this paper compares the density of two adjacent solutions until the error between the two is very small. Based on the iterative calculation, the d- and q-axis inductance is obtained. The finite element method and experiment are employed to validate the analytical model.

Hybrid Analytical Model for Predicting the Electromagnetic Losses in Surface-Mounted Permanent-Magnet Motors

Hybrid Analytical Model for Predicting the Electromagnetic Losses in Surface-Mounted Permanent-Magnet Motors

Permanent magnet synchronous motor demagnetization fault diagnosis based on leakage radial magnetic density

A method of demagnetization fault diagnosis of permanent magnet synchronous motors is proposed by measuring the radial magnetic density of the leakage field at the external space point of the motor. The method enables non-invasive diagnosis of motor permanent magnet demagnetization faults compared to other methods. In this paper, an analytical model of the radial magnetic density of the leakage field of a surface-mounted permanent magnet synchronous motor under no-load conditions is proposed, and its accuracy is verified by simulation. The influence mode of demagnetization fault on the radial magnetic density of the leakage field is analyzed, which provides a new idea for the diagnosis of motor demagnetization fault.

Active-Damping-Based Field-Weakening Control Strategy With Voltage Angle Regulation for High-Speed SPMSM Drive

The field weakening (FW) control strategy with voltage angle regulation has the advantages of fast speed and current response by directly decoupling the voltages. For suppressing the current harmonics, this article proposes a novel active-damping based FW control strategy for high-speed surface-mounted permanent magnet synchronous motor (SPMSM) drives. The resonant issue in the voltage-angle regulated system is analyzed, and the d-axis current is adopted to compensate the voltage angle, which introduces the additional impendence at the resonant frequency to reduce the d-q axis current harmonics. An offline coefficient design method based on the frequency characteristic and step response is proposed to construct the contour map seeking for optimal coefficients, which achieves significant reductions on current harmonics and improves the robustness of the proposed method on mismatches of motor parameters. The damping ratio of the current loop is determined by the integral coefficient with a wider range. Hence, the adaptability of the FW voltage angle regulation can be guaranteed under different speed and load conditions. The effectiveness of the proposed strategy is verified on the 6-kW high-speed SPMSM platform.

Volume optimization of high-speed surface-mounted permanent magnet synchronous motor based on sequential quadratic programming technique and analytical solution

This study proposes an innovative approach that integrates the subdomain method with sequential quadratic programming (SQP) to optimize the volume of a high-speed surface-mounted permanent magnet synchronous motor in an air compressor operating at 110 000 rpm. Unlike conventional optimization tools that often rely on finite element analysis (FEA) software, by leveraging the subdomain method for electromagnetic modeling, we obtain an analytical solution that rapidly represents the behaviors of the motor. Subsequently, the SQP technique is applied to optimize the volume of the model while satisfying design constraints. The proposed model is verified by FEA simulation.

Synthesis of Relative Permeance for Analysis and Design of Multislotted Surface-Mounted Permanent Magnet Motor

Synthesis of Relative Permeance for Analysis and Design of Multislotted Surface-Mounted Permanent Magnet Motor

Optimization Design of Surface-mounted Permanent Magnet Synchronous Motors Using Genetic Algorithms

The permanent magnet synchronous motor (PMSM) has gained widespread popularity in various industrial applications due to its simple structure, reliable performance, compact size, high efficiency, and adaptability to different shapes and sizes. Its exceptional characteristics have made it a focal point in industrial settings. The PMSM can be categorized into two primary types based on the arrangement of the permanent magnets (PM): interior permanent magnet (IPM) and surface-mounted permanent magnet (SPM). In the IPM, the magnets are embedded into the rotor, while in SPM, they are mounted on the rotor's surface. The utilization of PMs eliminates the need for excitation currents due to their high flux density and significant coercive force. This absence of excitation losses contributes to a notable increase in efficiency. In this study, a multi-objective optimal design approach is introduced for a surface mounted PMSM, aiming to achieve maximum efficiency while minimizing material costs. The optimization task is accomplished using a genetic algorithm. Furthermore, the motor designs are simulated using the finite element method (FEM) to assess and compare designs before and after the optimization process.