Ferrite Assisted Synchronous Reluctance Machines: a General Approach

A general approach to the design of high performance ferrite-assisted synchronous reluctance motors is presented. Reference is made to a rectified rotor structure, with multiple flux barriers, designed to optimize the performance and the exploitation of the PM material. The key design issue of de-magnetization is analytically investigated, pointing out the maximum allowed current loading, depending on temperature and machine dimensions. Such current limit is then compared with the one imposed by the thermal constraint. The analysis shows that low and medium size machines tend to be robust against demagnetization, while larger machines are more at risk. The theoretical analysis is confirmed by finite-elements via an example machine desig

Design of a multi-layer interior ferrite permanent magnet synchronous machine for traction applications

A novel design of interior ferrite permanent magnet synchronous machine with multi-layer configuration is proposed for traction applications. Although the ferrite magnet can be disadvantaged by its low residual flux density and energy product, it is proposed that flux-focusing and multi-layer configurations can be utilized to harness both permanent magnet (PM) torque and reluctance torque to recoup the loss of the PM torque due to its intrinsic property. The machines with up to three-layer magnets are presented and evaluated comprehensively. The results suggest that the two-layer machine provides the best performance among the three configurations. Furthermore, compared against a commercial rare-earth equivalent, the proposed ferrite machine is shown to have nearly the same torque with 32% less electromagnetic losses. The findings underpin interior ferrite permanent magnet synchronous machine as an attractive alternative for traction application

Design of synchronous reluctance motor with permanent magnets

V dnešní době je kladen vysoký nárok na účinnost elektrických zařízení a to jak ze strany provozovatele, tak i legislativy. Nejlepší účinnosti dosahují synchronní motory s permanentními magnety umístěnými na povrchu rotoru (SMPM), se kterými lze i u malých motorů dosáhnout účinnosti nad 90%. Nicméně tyto motory jsou z důvodů použití magnetů ze vzácných zemin, např. NdFeB, drahé a jsou schopny provozu pouze s frekvenčním měničem. Z cenových důvodů jsou hledány levnější alternativy k SMPM motorům. Jedním z typů motorů, kterým lze SMPM nahradit je synchronní reluktanční motor s permanentními magnety (PMASR). Tento motor je cenově výhodnější, protože používá menší množství magnetů, při zachování podobných, mnohdy i lepších vlastností, nicméně neodpadá potřeba použití frekvenčního měniče. Navíc je zde možnost použití levnějších feritových magnetů a tím ještě výrazněji snížit cenu motoru. V této práci bude PMASR topologie popsána důkladněji včetně elektromagnetického návrhu metodou konečných prvků. Bude provedena i mechanická analýza zvoleného optimálního modelu. Výsledky dosažené metodou konečných prvků budou následně porovnány s analytickým modelem. Z navrženého modelu bude vyroben prototyp a naměřené výsledky budou porovnány s výpočty.In these days a huge emphasis is put on efficiency of electric devices, both from the side of the owner as well as from the legislation. In the case of electric motors the best efficiency can be achieved with a surface mounted permanent magnet (SMPM) motor, which may be, even in the case of small machines, higher than 90%. Unfortunately, these motors are expensive, because rare earth magnets, such as neodymium magnets, are used, and use of the AC drive system is required. Because of its high price, engineers are trying to find a cheaper machine with parameters similar to SMPM solution. Permanent magnet assisted synchronous reluctance (PMASR) motor is one possible replacement for SMPM. This machine is cheaper, because smaller amount of magnets and still similar or even better characteristics could be achieved, but still the AC drive needs to be used. With PMASR topology it is possible to use low-cost ferrite magnets to replace expensive neodymium magnets, thus the machine will be cheaper. In this work, there will be PMASR topology explained more thoroughly, including the electromagnetic design process. Analytical analysis will be performed on a chosen optimal model. Results of the FE analysis will be evaluated with the analytical model. The prototype will be manufactured from the optimal designed model. The measured data from the prototype will be compared with the calculated data.

Multipolar Ferrite Assisted Synchronous Reluctance machines: a general design approach

A closed-form per-unit formulation for the design of surface-mounted permanent-magnet motors having high numbers of poles is hereby proposed. The analytical expression of machine inductances is presented, covering distributed and concentrated winding configurations. This paper addresses how the slot/pole combination, the geometric variables, and the number of poles are related to the average torque, the Joule loss, and the power factor. The performance of distributed and concentrated winding machines is analytically compared, in normalized quantities. Last, the design approach is tested on four design examples, including all winding types, and is validated by finite-element analysis

Reduced--cost Permanent Magnet mottor drives: a comprehensive design procedure and a universall approach to the magnettiic modell identification and conttol

This research deals with the design, identification and control of Permanent Magnet Synchronous motor drives. Throughout the project, motor and control designs have been straightly integrated in order to meet the challenging requirements, typically coming from the industrial world. Namely, the purposes leading this research activity are: cost-reduction and standardization of both design and control tasks into straightforward and universal procedures. As a deeper insight, this work proposes a comprehensive procedure for the design of reduced-cost Permanent Magnet based electrical machines and a universal control technique, requiring minimum calibration and a simplified preliminary commissioning stage. The recent price volatility of rare earth raw materials has been compelling designers and manufacturers of electric motors to find out or re-evaluate alternative machine topologies, using either a reduced amount of such rare-earth magnets or lower energy density magnetic materials, such as hard ferrites, still providing for high-performance technologies. This thesis is about facing this issue, while enhancing general approaches to the optimal design of Permanent Magnet Synchronous machines via fully-analytical models showing a twofold purpos

Design of Ferrite Assisted Synchronous Reluctance machines robust towards demagnetization

The design of ferrite-assisted synchronous reluctance machines is investigated, with particular attention to the pivotal aspect of avoiding irreversible de-magnetization. Geometric rules for obtaining a robust design are proposed and described analytically. The safe operating area is quantified in terms of the corresponding maximum electrical loading. Such demagnetization limit shows to be depending on the operating temperature and the machine size. Furthermore, the comparison between the continuous load and de-magnetization conditions shows that low and medium size machines can be stiffer against demagnetization, with respect to larger machines, and have room for transient overload. The analysis is validated by finite-elements and a design example is given, namely a twelve poles direct-drive machine, rated 910 Nm, 200 rpm

Optimised Design of Permanent Magnet Assisted Synchronous Reluctance Machines for Household Appliances

This paper is focused on the design, optimisation and control of a permanent magnet assisted synchronous reluctance machine (PMaSynRel) for low cost high efficiency household appliances, in particular a motor for washing machine. The design and optimisation of the motor aims at maximising the torque produced and power factor, while minimise torque oscillations and the losses, thus improving the efficiency. A campaign of tests has been carried out on the prototype of the optimised machine, comparing finite element results and experimental measurements as a validation of the proposed design. In addition, torque ripple measurements are confirming that the solution proposed is meeting the optimisation design targets. The outcomes of this project are demonstrating that PMaSynRel drives are a suitable candidate for white goods sector, and that the proposed design is able to boost the performance and efficiency class with respect to the state-of-the-art solutions

Investigation of novel multi-layer spoke-type ferrite interior permanent magnet machines

The permanent magnet synchronous machines have been attracting more and more attention due to the advantages of high torque density, outstanding efficiency and maturing technologies. Under the urges of mandatory energy efficiency requirements, they are considered as the most potential candidates to replace the comparatively low-efficient induction machines which dominate the industrial market. However, most of the high performance permanent magnet machines are based on high cost rare-earth materials. Thus, there will be huge demands for low-cost high-performance permanent magnet machines. Ferrite magnet is inexpensive and abundant in supply, and is considered as the most promising alternative to achieve the goal of low cost and high performance. In consideration of the low magnetic energy, this thesis explored the recent developments and possible ideas of ferrite machines, and proposed a novel multi-layer spoke-type interior permanent magnet configuration combining the advantages of flux focusing technique and multi-layer structure. With comparable material cost to induction machines, the proposed ferrite magnet design could deliver 27% higher power with 2-4% higher efficiency with exactly the same frame size. Based on the data base of International Energy Agency (IEA), electricity consumed by electric machines reached 7.1PWh in 2006 [1]. Considering that induction machines take up 90% of the overall industrial installation, the potential energy savings is enormous. This thesis contributes in five key aspects towards the investigation and design of low-cost high-performance ferrite permanent magnet machines. Firstly, accurate analytical models for the multi-layer configurations were developed with the consideration of spatial harmonics, and provided effective yet simple way for preliminary design. Secondly, the influence of key design parameters on performance of the multi-layer ferrite machines were comprehensively investigated, and optimal design could be carried out based on the insightful knowledge revealed. Thirdly, systematic investigation of the demagnetization mechanism was carried out, focusing on the three key factors: armature MMF, intrinsic coercivity and working temperature. Anti-demagnetization designs were presented accordingly to reduce the risk of performance degradation and guarantee the safe operation under various loading conditions. Then, comparative study was carried out with a commercial induction machine for verification of the superior performance of the proposed ferrite machine. Without loss of generality, the two machines had identical stator cores, same rotor diameter and stacking length. Under the operating condition of same stator copper loss, the results confirmed the superior performance of the ferrite machine in terms of torque density, power factor and efficiency. Lastly, mechanical design was discussed to reduce the cost of mass production, and the experimental effort on the prototype machine validates the advantageous performance as well as the analytical and FEA predictions