Spoke-type Permanent Magnet Synchronous Machine Research Articles

Investigation of Torque and Reduction of Torque Ripples through Assisted-Poles in Low-Speed, High-Torque Density Spoke-Type PMSMs

In this article, rotor designs utilizing assisted-poles are investigated for a high-torque density spoke-type permanent magnet synchronous machine (PMSM) with fractional slot concentrated winding (FSCW) to explore the rich air-gap magnetic field harmonics and torque generation mechanism. Due to their higher average torque output, spoke-type PMSMs with FSCW are increasingly used in high-torque density applications. However, slot harmonics generate torque ripples that are difficult to eliminate in FSCW spoke-type PMSMs. Removing slot harmonics from the stator or winding results in a large drop in torque since their winding factors are identical to those of the main harmonic. Therefore, rotor designs having assisted-poles (symmetrical and asymmetrical) are investigated in this work to mitigate slot harmonics and minimize torque ripples. Firstly, the air-gap flux density is analyzed for the machines having assisted-poles, and a model of interaction between the stator and rotor-MMF harmonics is created and validated through Finite element analysis (FEA) to analyze the torque production mechanism. In addition, an analytical relationship between the assisted-poles’ dimensions and the generated torque harmonics is proposed. Furthermore, a generalized torque ripple reduction concept for the FSCW spoke-type PMSM having asymmetrically designed assisted-poles is presented. The proposed design and optimization method are validated through analytical calculations and FEA simulations, and a brief comparative analysis is presented for the analyzed machine prototypes. It has been established that the machine designed by applying the proposed asymmetrical assisted-poles can achieve a reduction in torque ripples while also significantly lowering cogging torque in comparison to the conventional spoke-type PMSMs and other spoke-type PMSMs with rotor having symmetrical assisted-poles.

Vibration Analysis of Delta-Connected PMSMs Using Lookup Table-Based Models—Influence of the 0-Sequence Component

In this article, a multiphysics simulation workflow based on the use of reduced-order models to decrease the computation time is presented. Using finite-element (FE) precomputed flux-linkage and lumped force lookup-tables in function of dq0 currents and rotor position, an electromagnetic model of a permanent-magnet synchronous machine (PMSM) is developed. Coupled to a mechanical state-space representation, the complete workflow allows to predict the vibrations of the motor. Using our model, the influence of the 0-sequence current on the vibration spectrum is investigated. A detailed description on the parameter identification for homogenized stator core of the considered 12-slot 10-pole delta-connected fractional-slot concentrated-winding spoke-type PMSM is also given. The numerical results are validated with experimental data for the machine at hand. Because of the large amount of FE data required, the workflow is best suited for the optimization of motor control schemes (instead of the initial design optimization) with the purpose of reducing the noise, vibration, and harshness.

The mathematical model of the thermal process in Spoke-Type Permanent Magnet Synchronous Machines

This paper presents an mathematical model for the prediction of temperature field distribution in spoke-type permanent magnet synchronous machines. The mathematical model takes into account radial heat transfer streams; it is presented as a boundary problem in a multilayer non-canonical region with conjugation conditions at the boundaries of the layers, with different thermal physical properties. The entire study area is divided into five types of simple subdomains, including a shaft, an inner fan-shaped magnet, an outer fan-shaped magnet, a slot opening and a slot. Moreover, on the border of the inner and outer fan-shaped magnets in slot opening and a slot, we have an perfect thermal contact. The problem is solved by the finite element method. Using the results of numerical experiments, the model allows you to control the temperature field of the machine, allows you to calculate the temperature distribution in its individual parts.

Development of Differing Extent Mesh Adaptive Direct Search Applied for Optimal Design of Spoke-Type PMSM

Optimal design of electric machines using finite-element analysis (FEA) necessitates too much computation time to maintain high accuracy. To reduce the computation time and obtain a global optimum in multi-modal problems, this paper presents differing extent mesh adaptive direct search (DEMADS). The proposed algorithm is classified into three groups according to the poll searching frame and mesh size for assigning a global and local searching. In particular, DEMADS shares information among solutions based on a parallel multi-start strategy for earlier stopping by deviation and checking revisits. The effectiveness of DEMADS has been validated and evaluated as the function call number and the convergence number at a global optimum using benchmarking function. Finally, it is applied to an optimization problem that minimize torque ripple of a spoke-type permanent magnet synchronous machine via FEA.

Semi-Analytical Magnetic Field Predicting in Many Structures of Permanent-Magnet Synchronous Machines Considering the Iron Permeability

This paper deals with an adaptable semi-analytical model to calculate the open-circuit and armature reaction field distributions as well as the electromagnetic performances in many structures of permanent-magnet synchronous machines (PMSMs). It is based on the multi-layer models considering the iron permeability with the convolution theorem (i.e., Cauchy’s product theorem) using the harmonic modeling technique (or the Maxwell–Fourier method). The 2-D semi-analytical model can be used for surface-mounted–inset-mounted or spoke-type PMSMs with different permanent-magnet (PM) magnetization patterns, winding structures, internal/external rotors, and slotless or slotted stators without the need to adopt the model equations to a specific PM machine type. For example, this scientific contribution has been applied to three types of PMSM with different topologies, viz.: i) slotted surface-mounted external rotor PMSM; ii) slotted surface–inset internal rotor PMSM; and iii) slotless external rotor spoke-type tangential PMSM. Finally, the results of semi-analytical method are compared with those found by the finite-element method.

Analytical Prediction of No-Load Stator Iron Losses in Spoke-Type Permanent-Magnet Synchronous Machines

This paper presents an analytical approach for the prediction of no-load stator iron losses in spoke-type permanent-magnet synchronous machines. The influence of bridge saturation is considered. According to the permeability distribution, the bridge is equivalent to fan-shaped saturation region with constant permeability. The magnetic equivalent circuit and iterative method are used to calculate the permeability. The motor is divided into six regions, i.e., shaft, inner saturation region, magnet, outer saturation region, air-gap, and slot. The air-gap magnetic field distribution is first calculated on the basis of Poisson's and Laplace's equations. Then, according to the flux paths, the stator core is divided into tooth and yoke. The magnetic densities of the tooth and yoke are obtained on the basis of the continuity of magnetic flux. Finally, the Bertotti model is employed to calculate the stator iron losses. The validity of the proposed method is verified by the finite element method.