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The traditional electromagnetic–thermal bidirectional coupling model (EMTBCM) of permanent magnet synchronous motors (PMSMs) requires a long time to solve, and the temperature-induced torque change is not accounted for in the finite element (FE) numerical calculation of the EM field. This paper presents a precise and efficient EMTBC reduced-order solution model. The specific methods are as follows: First, a torque control technology based on the current injection method is proposed for determining the effect of temperature on the properties of EM materials and EM torque in an EM field, and the accuracy of the FE numerical calculation model is improved. Second, we use the improved EM field finite element numerical calculation model (FEMNCM) to analyze the correlation between the EM loss, the temperature, and the load, and we replace the FEMNCM with the EM field reduction model using the least-squares method. Then, we analyze the law of the PMSM's internal temperature distribution. We choose the GA-BP algorithm with as few samples as possible and a high accuracy and stability to build the regression prediction model of the temperature field. We use this regression prediction model to replace the complex temperature field calculation. After analyzing the EMTBCM solution strategy, the original complex EMTBC numerical calculation model is substituted with iterations of the magnetic field reduction model and the temperature field regression prediction model. The FE numerical calculation is then used to validate the reduced-order model. The proposed model is validated through numerical simulations. The numerical results indicate that the proposed reduced-order EMTBC model in this paper is accurate and computationally efficient. [ABSTRACT FROM AUTHOR]

When a permanent magnet synchronous motor (PMSM) is designed according to the traditional motor design theory, the performance of the motor is often challenging to achieve the desired goal, and further optimization of the motor design parameters is usually required. However, the motor is a strongly coupled, non-linear, multivariate complex system, and it is a challenge to optimize the motor by traditional optimization methods. It needs to rely on reliable surrogate models and optimization algorithms to improve the performance of the PMSM, which is one of the problematic aspects of motor optimization. Therefore, this paper proposes a strategy based on a combination of a high-precision combined surrogate model and the optimization method to optimize the stator and rotor structures of interior PMSM (IPMSM). First, the variables were classified into two layers with high and low sensitivity based on the comprehensive parameter sensitivity analysis. Then, Latin hypercube sampling (LHS) is used to obtain sample points for highly sensitive variables, and various methods are employed to construct surrogate models for variables. Each optimization target is based on the acquired sample points, from which the most accurate combined surrogate model is selected and combined with non-dominated ranking genetic algorithm-II (NSGA-II) to find the best. After optimizing the high-sensitivity variables, a new finite element model (FEM) is built, and the Taguchi method is used to optimize the low-sensitivity variables. Finally, finite element analysis (FEA) was adopted to compare the performance of the initial model and the optimized ones of the IPMSM. The results showed that the performance of the optimized motor is improved to prove the effectiveness and reliability of the proposed method. [ABSTRACT FROM AUTHOR]

A novel asymmetric spoke-type interior permanent magnet (AS-IPM) machine is proposed in this paper. It utilizes the magnetic-field-shifting (MFS) effect to improve the torque performance, which achieves a high utilization ratio of both permanent magnet (PM) torque and reluctance torque. In addition, a general pattern of rotor topologies is proposed to represent all possible machine structures. Various rotor structures can be obtained by changing the design parameters of the general pattern. A non-dominated sorting genetic algorithm II (NSGA-II) is adopted to automatically search for optimal rotor configurations. With the aid of the optimization program, an asymmetric spoke-type rotor structure with improved performance is obtained. To showcase the advantages of the proposed machine, the electromagnetic performance is compared between a conventional spoke-type interior permanent magnet (S-IPM) machine and a proposed AS-IPM machine. The finite-element simulation results show that the optimal design of the AS-IPM performs a 7.7% higher output torque ripple due to the MFS effect while the total PM volume remains the same. Meanwhile, the torque ripple of the proposed structure is significantly reduced by 82.1%. [ABSTRACT FROM AUTHOR]

A high-end permanent magnet (PM) synchronous motor's cogging torque is a significant performance measure (PMSM). During the running of the motor, excessive cogging torque will amplify noise and vibration. Therefore, the cogging torque must be taken into account while optimizing the design of motors with precise motion control. In this research, we proposed a local optimization-seeking approach (RSM+NSGA-II-LR) based on Response Surface Methodology (RSM) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II), which reduced the cogging torque of a permanent magnet synchronous motor (SPMSM). To reduce the complexity of optimization and increase its efficiency, the sensitivity analysis method was utilized to identify the structural parameters that had a significant impact on the torque performance. Second, RSM was utilized to fit the functional relationship between the structural parameters and each optimization objective, and NSGA-II was integrated to provide the Pareto solution for each optimization objective. The solution with a greater average torque than the initial motor and the lowest cogging torque was chosen, and a new finite element model (FEM) was created. On the basis of the sensitivity analysis, the structural factors that had the highest influence on the cogging torque were selected, and the RSM is utilized for local optimization to lower the cogging torque as much as feasible. The numerical results demonstrated that the optimization strategy presented in this study effectively reduced the cogging torque of the motor without diminishing the motor's average torque or increasing its torque ripple. [ABSTRACT FROM AUTHOR]

As asymmetric interior permanent magnet synchronous motor (AIPMSM) has excellent performance but complicated topological structure, a novel high-resolution encoding and edge smoothing method is proposed for topology optimization of the asymmetric rotor of interior permanent magnet synchronous motor (IPMSM) in this study. This method aims to solve complex electromagnetic design problems with time-dependent performance through a multi-objective genetic algorithm (MOGA) integrated with a high-resolution encoding and edge smoothing method. The complex structure is represented by a high-resolution image-like matrix and then vectorized by the edge smoothing method. Therefore, the commonly used discrete binary encoded variables related to the finite element (FE) model are replaced with a vectorized topological structure and other control variables. In this sense, high-resolution matrix and edge smoothing methods are used for the first time to represent the rotor topology of AIPMSMs. Compared with the traditional topology optimization method, the proposed method has the advantage of expressing more complex and vectorized topological structures; meanwhile, the obtained performance is accurate and trustworthy using conventional FE simulation. Numerical results show that a stable convergence is achieved with the avoidance of checkerboards and material overlapping. It is shown that the proposed method can find solutions with better performances, in comparison with the reference model. [ABSTRACT FROM AUTHOR]

A line-start permanent magnet (LSPM) machine can be regarded as the integration of an induction motor and a permanent magnet synchronous motor (PMSM), so it has both self-starting capability as the induction motor and high efficiency as PMSM. As the cage winding on the rotor of LSPM only works at the starting process, it competes with permanent magnets for the space of a rotor. To solve this paradox, a steel-bar starting cage-based LSPM machine is proposed and analyzed in this article. Steel has larger resistivity than aluminum and copper, which can increase the starting torque and reduce the impact current of cage winding at the starting stage. Due to high permeability of steel, magnetic flux can also flow through steel-bar cage winding at synchronous speed. A steel-bar starting cage and a traditional aluminum starting cage winding are compared based on a four-pole LSPM machine using finite-element analysis (FEA) in this article. It is verified that although the self-starting capability of steel-bar cage winding is reduced due to the leakage flux, the performance at synchronous speed such as torque density and torque ripple is improved. [ABSTRACT FROM AUTHOR]

To address such challenges as an uncertain number of demagnetization poles of the permanent magnet synchronous motor (PMSM) and cases in which the fault cannot be located, this paper proposes a fault identification and location methodology based on the analysis of the motor stator current. First, the influence of the irreversible demagnetization of permanent magnets on the analytical model of the back electromotive force (Back-EMF) of the rotor in a single motor stator slot is analyzed. Moreover, considering the topology of the motor, the influence of the demagnetization fault on the stator phase current and branch current is analyzed. Since the stator phase currents cannot diagnose the partial demagnetization faults of PMSM with some topological structures, the stator branch current is selected as the signal for the identification and localization of the demagnetization fault. Secondly, the demagnetization fault diagnosis and mode recognition of the motor are carried out through the amplitude of the real-time branch current and the harmonic components of the PMSM. A sample database of demagnetization faults is established through calculation and normalization of the residual value of the stator branch current and the branch current of the healthy motor after demagnetization in one pole order. The fault threshold is obtained by analyzing the residual of the branch current of uniform demagnetization and the Pearson correlation coefficient of the fault sample database. Then, the correlation coefficient between the real-time branch current residual value of PMSM and the fault sample database is analyzed, and the number of demagnetization poles and the fault location are determined by the number and location of the calculated correlation coefficient exceeding the threshold. Finally, the feasibility and effectiveness of the proposed method are verified by the finite element analysis (FEA) results. [ABSTRACT FROM AUTHOR]

Here, a novel DC‐excited doubly salient machine with a claw‐shaped modular stator and three‐dimensional (3D) complementary magnetic circuit is proposed for wind power generation application. The key is to artificially construct a 3D complementary structure to suppress torque ripple and employ auxiliary slot‐opening PMs to relieve DC‐saturation in the stator core and improve overload capability. The novel 3D complementary structure provides an alternative magnetic path for the main flux, so the flux leakages in the air gap at open‐circuit position are effectively cancelled, and the flux in the yoke remains relatively constant. Hence, the output torque ripple is suppressed. Furthermore, the saturation issue in the stator is solved with auxiliary permanent magnets which have opposite magnetization direction to that of DC field excitation. Therefore, the torque capacity of the machine is improved. Here, the machine structure and operation principle are introduced, and a 2D equivalent model is also developed to replace the 3D model to improve the calculation efficiency. Multi‐objective optimization algorithm is developed to improve the performance of this new machine. The validity of machine design is finally verified with 2D and 3D finite element analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a novel direct-drive dual-PM motor for electric automatic guided vehicles (AGV). The proposed motor has split teeth on stator and dual PMs in stator and rotor sides, which contributes to reduced torque ripple, and enhanced torque. The airgap field of the proposed motor is analyzed theoretically, and the slot/pole selection guide line is concluded. The simulation results of the airgap flux density are shown and Fourier Transformation (FFT) analysis results agree well with the theoretically analyses results. Besides, the effects of design parameters of the proposed motor to the performances of the proposed motor are investigated. And it is found that reduced slot open could produce improved efficiency and decreased torque ripple. The efficiency of the proposed motor is relatively high within the operation range. A corresponding prototype is fabricated and the experiment validates the design. [ABSTRACT FROM AUTHOR]

In this paper, a new permanent magnet (PM) linear motor is proposed. This motor has a special structure with complementary stator flux, which helps to reduce the flux leakage and improve the utilization of the PM. The PMs are installed in a leaning manner, which increases the effective area of the PMs and enhances the field excitation. Hence, the force density of the motor can be improved and it will be, especially suitable for applications within a limited space. The motor structure and working principle are first explained. The design of the motor is then comprehensively investigated. An electromagnetic optimization method based on tabu search algorithm and finite-element method is proposed for the motor to improve its force density. [ABSTRACT FROM AUTHOR]

A novel bidirectional flux-modulation permanent magnet (BFMPM) machine for stand-alone dc wind power generation is proposed in this paper. The key is to control the inner rotor position with a small servo motor, and with the bidirectional flux-modulation effect, the resultant induced voltages in two sets of stator windings can be adjusted accordingly. Consequently, in a wide wind speed range, the various-speed constant-amplitude-voltage operation is realized. The novel structure has two major merits. First, it has high reliability without the maintenance problems caused by mechanical gearboxes, slip ring assembly, and brushes. Second, the proposed system requires a low-cost uncontrolled diode rectifier, which enhances the reliability and reduces the cost of the system. The analytical model and operation principle of the BFMPM machine are illustrated and the simulation results using a finite-element method is presented. A prototype is optimized and fabricated. The experimental results agree well with the simulation results and verify the correctness of the analytical model and the effectiveness of the proposed structure. Therefore, the novel structure offers a potential solution to provide a stable dc power for the standalone condition, such as remote area and offshore island. [ABSTRACT FROM AUTHOR]

In this paper, a novel modular linear double-stator biased flux (LDSBF) machine is proposed for wave power generation. The operation principle based on flux path analysis is presented. And stator/rotor pole number combinations are discussed by using coil flux analysis. The modular LDSBF machine has better flux path distribution than its counterpart, namely, linear biased flux permanent magnetic machine. More than that, the topology of the modular LDSBF machine makes it feasible to modular design and easy assembly. The electromagnetic characteristics of four types of linear machines are analyzed and compared by using time-stepping finite-element method. The comparative study shows that modular LDSBF machine with improved performance is a good potential design for wave power generation. [ABSTRACT FROM AUTHOR]

In this paper, both the steady-state and dynamic performances of the double-stator permanent magnet brushless (DS-PMB) machines, including the surface-mounted topology (DS-SPMB) and the interior topology (DS-IPMB), are quantitatively compared with that of the traditional single-stator SPMB (SS-SPMB) machine. Based on the same electric loading and magnetic loading, the DS-SPMB and DS-IPMB machines are designed to have the same output power, while the DS-SPMB and SS-SPMB machines are of the same peripheral dimensions. The steady-state and transient characteristics of these machines are simulated by using the circuit-field-torque time-stepping finite element method. Finally, the preferred machine, namely, the DS-SPMB one, is prototyped and tested for experimental verification. [ABSTRACT FROM AUTHOR]

This paper systematically studies a new kind of PM machines with both stator and rotor PM excitations, namely, dual-PM excited machines. The key is to rely on the PM-iron structure in the machine to provide both PM excitation and flux modulation. Besides the fundamental field component in the air-gap, some other predominant harmonics introduced by the flux modulating effect can also contribute to the electromagnetic torque production. Therefore, this kind of machines can be designed with high torque density. Four dual-PM excited machine concepts with the same rotor configuration but different stator structures are comparatively studied, which include double-stator PM machine, stator multitooth-PM machine, stator slot-PM machine, and stator tooth-PM machine (STPM). Based on the flux modulating effect, the general design principle of the dual-PM machines is proposed in this paper. Through analytically investigating the air-gap field harmonics, the physical insight of the dual-PM machines is brought forward. All the four machines are optimized using an improved Tabu search coupled with finite element method, and their electromagnetic performances are comprehensively studied and compared. A prototype of STPM is manufactured. Experimental tests are conducted and the results well verify the electromagnetic design. [ABSTRACT FROM AUTHOR]

This paper proposes a new brushless contra-rotating power split transmission (CR-PST) system for the direct-drive wind power generation. The core element of this system is a doubly fed dual-rotor flux-modulation permanent magnet machine, which has two contra-rotating rotors connected with two wind blades to absorb the wind energy, and two sets of stator windings to realize torque split between the two shafts. This proposed CR-PST system has compact structure and bidirectional flux-modulation design, as well as increased wind power conversion efficiency. Compared with the conventional wind turbine system, which can only work with single maximum power point tracking (MPPT) control strategy, the proposed CR-PST system can collect increased wind energy with dual MPPT method for the given wind speed. Time-stepping finite-element method is used to analyze the steady and dynamic performance of the proposed system and the control strategy is verified by experiments and simulation results. [ABSTRACT FROM PUBLISHER]

In this paper, an efficient and effective magnetic circuit model is developed for the analysis of a magnetless double-rotor flux switching motor. First, a magnetic circuit network for the proposed machine is built, and formulas for the calculation of the magnetic components in the circuit, including the permeances of teeth, yokes, slots, leakage permeances, and air-gap permeances, are derived. Then, by applying Kirchhoff’s current law to each node in the network, nodal analysis is used to solve the matrix equation. All the circuit variables, and hence the complete motor magnetic characteristics are being considered. When the rotor rotates, the air-gap permeances are adjusted accordingly, and the above calculations are repeated, so as to find the complete static performance of the motor. Last, the validity and the effectiveness of the proposed method are verified using both the experimental results and the simulation results obtained from the time-stepping finite-element method. [ABSTRACT FROM AUTHOR]

Electric motors fabricated with aluminum–nickel–cobalt (AlNiCo) permanent magnets (PMs) can be operated over a wide speed range, as the strong nonlinear demagnetization characteristics of AlNiCo allow effective and efficient airgap flux control. This paper presents a linear hysteresis model which is derived from the Preisach model for AlNiCo PMs, to be incorporated into the time-stepping finite element method to study the motor performance, especially transient performance, accurately and effectively. The proposed method can significantly reduce the computing time without scarifying the accuracy of the Preisach model. The validity and accuracy of the proposed method are verified by both simulation and experimentation. [ABSTRACT FROM PUBLISHER]

In a permanent magnet brushless (PMBL) motor, any special structural design in the stator lamination may induce asymmetry in the magnetic circuit to result in intrinsic imbalanced force. Likewise, an asymmetrical phase winding arrangement may also induce imbalanced force in the motor when the armature currents are flowing. This paper presents the analysis of the imbalanced forces of two PMBL motors in an electric coolant pump system with magnetic and/or electric asymmetries using both numerical simulation and prototyping test. The results confirm the validity of force calculation method and illustrate the contributions of magnetic and electric asymmetries to the imbalanced forces in PMBL motors. [ABSTRACT FROM AUTHOR]

This paper presents a novel magnetless double-rotor flux switching motor for low cost cooling fan application. By creatively incorporating concentrated toroidal windings into a double-rotor middle-stator structure, the proposed motor not only realizes the flux switching feature, but also shortens the end-windings to improve its operational efficiency. To achieve a better performance, the motor dimensions, especially the stator and rotor pole arcs, are optimized. Meanwhile, with the introduction of a stepped air-gap, the torque at any rotor position is boosted and problems with zero output torque at starting is successfully avoided. The final optimized motor is analyzed using finite element method, and its validity is confirmed by the simulation results. [ABSTRACT FROM AUTHOR]

In this paper, an electric machine with dual permanent magnet (PM) structures in both stator and rotor is proposed. Multi-pole PMs are buried both in stator and rotor slots of the proposed machine and the magnetic field is modulated through the stator and rotor teeth. This machine with dual magnetic flux modulation can be categorized as one special case of flux-modulating machines. A time-stepping finite-element method combined with space vector pulse width modulation-based vector control method is used to analyze the steady-state and transient performance of the machine and its control system. [ABSTRACT FROM AUTHOR]

A novel solution for sensorless starting of conventional surface mounted PM motors is proposed. The strategy of the proposed scheme is to creatively formulate a combination of electromagnetic field with transient finite element method (FEM). The proposed solution is an improvement over and above conventional methods in that it is based on rotor position detection at zero speed with high frequency signal injection and back EMF detection. Previous researches tend to consider the induced signal from different winding terminals independently. The proposed methodology however exploits the induced voltage signals from two of the motor winding terminals, using the third terminal as the signal injection point. The strategy also eliminates the process of polarity tests. The relationship between the dependency of induced signals and the rotor position angle is summarized, and a simple motor starting scheme is proposed. Effects arising from the transient characteristics of the injected/induced signals are fully addressed using FEM. [ABSTRACT FROM PUBLISHER]

Hysteresis effects of laminated steel materials on the detent torque in permanent magnet (PM) motors are described physically. There are many methods to simulate hysteresis effects. However most studies only focus on loss calculation but not on other important issues. Based on field orientation interpolation method, four-quadrant hysteresis effects are taken into consideration in the proposed cogging torque computation. Simulation results using finite element analysis (FEA) show that laminated materials with high hysteresis effects give higher detent torque when compared to those with narrow hysteresis loops. Two brushed type PMDC motors, with a 4-pole, 22-slot configuration and with different laminated steel materials, are built, and their test data are used to validate the analysis. [ABSTRACT FROM AUTHOR]

Vernier permanent magnet (VPM) machines can be utilized for direct drive applications by virtue of their high torque density and high efficiency. The purpose of this paper is to develop a general design guideline for split-slot low-speed VPM machines, generalize the operation principle, and illustrate the relationship among the numbers of the stator slots, coil poles, permanent magnet (PM) pole pairs, thereby laying a solid foundation for the design of various kinds of VPM machines. Depending on the PM locations, three newly designed VPM machines are reported in this paper and they are referred to as 1) rotor-PM Vernier machine, 2) stator-tooth-PM Vernier machine, and 3) stator-yoke-PM Vernier machine. The back-electromotive force (back-EMF) waveforms, static torque, and air-gap field distribution are predicted using time-stepping finite element method (TS-FEM). The performances of the proposed VPM machines are compared and reported. [ABSTRACT FROM AUTHOR]

The current constraint and robustness improvement of the speed-current single-loop controlled permanent magnet synchronous motor (PMSM) are investigated. To begin with, a speed-current single-loop control for PMSM is proposed based on a novel proportional integral derivative (PID) controller. Additionally, a barrier penalty factor is introduced in the differential term of the PID to constrain the q-axis current. Moreover, an adaptive extended state observer (AESO) is proposed to attenuate the peak problem and compensate for the mismatched disturbances of the non-cascade-controlled PMSM. A rigorous stability analysis is conducted for the proposed system. Finally, extensive comparative simulations and experiments are performed among the proportional-integral (PI), PI-based ESO (PI-ESO), sliding mode control (SMC), and the proposed strategy to demonstrate better transient performance and higher robustness. Parametric perturbation experiments further demonstrate the strong robustness of the proposed method. • Speed-current single-loop control with overcurrent protection and an adaptive ESO is investigated for PMSM. [ABSTRACT FROM AUTHOR]