Comparative Study of Linear Variable Flux Reluctance Machine with Linear Wound Field Flux Reversal Machine

As members of doubly salient magnetless linear machines,linear variable flux reluctance(LVFR)and wound field flux reversal(LWFFR)machines inherit the merits of conventional magnetless linear machines such as low cost,high flux adjustment capability and high reliability.Furthermore,like linear switched reluctance machine,they have a very simple and compact long secondary,which are very attractive for long stroke applications.However,low force capability is their major defect.To solve this issue,new LVFR and LWFFR machine topologies were proposed in recent work,while lacking studies on their force improvement mechanism and further force evaluation.In this paper,LVFR and LWFFR machines with improved force performance are comparatively studied with the emphasis on their force capabilities.The operation principle of the two machines is analyzed based on magnetic field harmonics produced by flux modulation.Contributions of air-gap flux density harmonic components to no-load back electromagnetic forces of the two machines are analyzed and the average force equation is derived.Moreover,force capabilities of the both machines are investigated by means of the time-stepping finite-element analysis to verify the theoretical analysis.

Fast Design Method of Variable Flux Reluctance Machines

In this paper,a fast design method is developed based on a combination of analytical and finite element(FE)methods for variable flux reluctance machines(VFRMs).Firstly,the feasibility of using analytical method in optimization under unsaturated condition is confirmed.Then,by applying the FE method,the influence of magnetic saturation is considered.Compared with the unsaturated case,the optimal split ratio for magnetically saturated case is increased by 1~1.2 times,the optimal rotor pole arc ratio varies within 0.33~0.44,and the stator pole arc ratio remains the same.Based on this,the optimal structural parameters can be initially set by analytical method and then refined by the FE method.Due to the fast speed of analytical method,less variable counts and narrowed variation ranges,the proposed method is significantly faster than the conventional pure FE based global optimization.Finally,the proposed method is used for optimizing the 6-stator-slots VFRMs having different numbers of rotor poles.The 6-stator-slot/7-rotor-pole(6s/7r)VFRM is found to have the highest torque density.It is prototyped and tested to verify the analyses.

一种基于自适应滤波的VFRM无位置传感器控制

可变磁通磁阻电机(variable flux reluctance machine,VFRM)的空间磁链谐波和逆变器非线性等因素会在扩展反电动势中产生谐波,进而降低无位置传感器的控制精度。为解决此问题,首先通过构建双曲正切函数滑模观测器,减小传统滑模观测器造成的高频抖振和相位延迟;然后分析了扩展反电动势谐波对转子位置估计的影响,并在此基础上提出了一种变步长最小二乘(least mean square,LMS)自适应滤波算法,准确地提取了扩展反电动势的基波分量,提高了转子位置和转速的估计精度。实验结果表明,所提算法与传统定步长LMS自适应滤波算法相比具有更好的控制性能。

混合励磁可变磁通磁阻电机齿槽转矩抑制研究

针对混合励磁可变磁通磁阻电机(hybrid excited variable flux reluctance machine,HEVFRM)齿槽转矩较高的问题,对6槽7极HEVFRM转子削极的方法进行了研究。建立空载气隙磁动势与磁导模型,计算空载气隙磁场中的谐波分布,通过比较原始转子、反余弦削极、反余弦加三次谐波削极与反余弦加三次、五次谐波削极转子空载气隙磁密谐波的幅值,削极转子结构可以降低高阶气隙磁密谐波幅值,来抑制齿槽转矩。结果表明,反余弦削极转子可以有效抑制齿槽转矩,将反余弦削极与谐波注入相结合可以进一步抑制齿槽转矩。其中,反余弦加三次、五次谐波削极转子结构可以抑制99.1%的齿槽转矩,而平均输出转矩仅降低4.5%。通过实验验证了反余弦削极转子可有效抑制6槽7极HEVFRM的齿槽转矩。

Quantitative Comparison of Electromagnetic Performance of Electrical Machines for HEVs/EVs

In this paper,various types of sinusoidal-fed electrical machines,i.e.induction machines(IMs),permanent magnet(PM)machines,synchronous reluctance machines,variable flux machines,wound field machines,are comprehensively reviewed in terms of basic features,merits and demerits,and compared for HEV/EV traction applications.Their latest developments are highlighted while their electromagnetic performance are quantitatively compared based on the same specification as the Prius 2010 interior PM(IPM)machine,including the torque/power-speed characteristics,power factor,efficiency map,and drive cycle based overall efficiency.It is found that PM-assisted synchronous reluctance machines are the most promising alternatives to IPM machines with lower cost and potentially higher overall efficiency.Although IMs are cheaper and have better overload capability,they exhibit lower efficiency and power factor.Other electrical machines,such as synchronous reluctance machines,wound field machines,as well as many other newly developed machines,are currently less attractive due to lower torque density and efficiency.

不等齿宽可变磁通磁阻电机齿槽转矩抑制

为了降低可变磁通磁阻电机(variable flux reluctance machines,VFRM)额定励磁电流下的齿槽转矩,对其产生原因进行分析,在通过磁场的傅里叶分析推导出VFRM齿槽转矩与电机结构参数关系的基础上,提出使用转子不等齿宽结合转子斜极的方法降低齿槽转矩。研究了转子不等齿宽降低齿槽转矩的原理,提供了不等齿宽选取的原则。通过对12槽10极VFRM有限元的研究表明,转子使用不等齿宽结合分段斜极后,齿槽转矩幅值由17.53 mN·m降低至0.78 mN·m,转矩脉动由10.79%降低至2.59%。最后,通过实验对不等齿宽方法进行了验证。

新型可变磁通磁阻电机振动和噪声研究与开关磁阻电机的比较(英文)

通过电磁和机械有限元方法计算并通过实验研究一种新型可变磁通磁阻电机的振动和噪声。这种新型电机使用与开关磁阻电机类似的定、转子冲片,但在定子侧放置一套直流励磁绕组;同时,用三相双极性桥式电路产生的正弦电流驱动定子电枢绕组。由于在二阶振动模态频率点附近的振动得到极大的降低,这种新型可变磁通磁阻电机所产生的振动和噪声得到了极大地削弱。实验证实相比开关磁阻电机,这种新型可变磁通磁阻电机在空载和负载下可以使声压级分别降低4dBA和8dBA。

计及电枢和零序回路电阻压降的可变磁通磁阻电机弱磁控制

在可变磁通磁阻电机的弱磁控制中,忽略电枢和零序回路上的电阻压降会影响弱磁区内参考电流的计算,这会导致电流环饱和,电机电流不能跟随给定值。在这种情况下,电机在弱磁区的输出功率会受到限制。为了解决此问题,提出一种计及电枢和零序回路电阻压降的弱磁控制方法。首先,该方法基于电压方程以及电压和电流的约束,利用拉格朗日极值法求取弱磁区内考虑电阻压降后的最优电流参考值的公式。其次,利用牛顿拉夫逊迭代法根据当前电机的状态计算出电流参考值。然后,考虑电阻压降后,弱磁区内参考电流的计算准确度得到提高,有利于可变磁通磁阻电机在弱磁区内的稳定运行。最后,通过实验结果验证了该方法的有效性。

变磁阻可控磁通永磁游标电机电磁性能分析

为了兼顾永磁电机低速、大转矩特性和恒功率区的运行范围,提出一种变磁阻可控磁通永磁游标(RVFCPMV)电机。以1台三相22/2对极RVFCPMV电机为例,介绍了RVFCPMV电机的拓扑结构。基于气隙磁通密度的调制,揭示了该电机具有低速、大转矩特性的实质,突破在电枢绕组中通入直轴去磁电流分量的传统弱磁方式,提出一种利用铁磁材料非线性导磁特性,通过调节励磁电流进而改变磁路磁阻方式实现永磁电机弱磁升速的方法。通过有限元方法对RVFCPMV电机进行了计算和分析,验证了该电机基速以下的低速、大转矩输出特性和基速以上的弱磁调速能力。

基于单桥臂励磁控制的可变磁通磁阻电机控制系统

提出一种基于单桥臂励磁控制的可变磁通磁阻电机(variable flux reluctance machine,VFRM)控制系统,与基于H桥控制励磁电流的VFRM控制系统相比,使用的开关器件少,在降低成本的同时也降低逆变器的损耗。基于单桥臂励磁控制的VFRM控制系统中的励磁电流通过电枢绕组中性点与第四桥臂,通过拉格朗日乘数法求得励磁电流和交轴电流最优分配。最后,对比了单桥臂励磁控制和H桥励磁控制的VFRM控制系统的损耗、效率等。结果表明,在相同的转矩和转速条件下,与H桥励磁控制的VFRM控制系统相比,逆变器损耗降低了50%,效率升高3.3%。

永磁辅助型可变磁通磁阻电机运行机理与特性分析

可变磁通磁阻电机具有调磁范围宽和可靠性高的优点,但无永磁体致使其转矩密度较低.为此,本文提出了一种永磁辅助型可变磁通磁阻电机,通过设计辅助永磁体,兼具可变磁通磁阻电机优点的前提下,提高电机转矩性能.重点围绕永磁辅助型可变磁阻电机的运行机理开展研究,分别推导励磁绕组、永磁体和电枢绕组单独工作时的气隙磁密,揭示磁场调制作用下各磁场谐波的匹配规律,探明励磁绕组励磁和永磁体励磁对转矩的作用机制,并确定有效工作波的阶次及相应的转速.然后,基于麦克斯韦应力张量法,求得每次工作波对转矩的贡献度.最后,加工制造样机,试验验证了电机运行原理和理论分析的正确性.