脉冲磁场发生器中用Braunbeck线圈的分析

研制一台用于肿瘤治疗的脉冲磁场发生器的关键单元是磁场线圈的设计和研制。为设计一种均匀区域更大、均匀度更高、工作更稳定的磁场线圈,在总结课题组前期工作的基础上,提出用一种4线圈系统的Braunbeck线圈替代传统的Helmholtz线圈。并对Braunbeck线圈的几何参数和中心磁场进行了理论计算、用COMSOL Multiphysics有限元软件进行内部磁场分布仿真以及研制出实物并对其性能进行了实测,结果显示该Braunbeck线圈工作性能稳定,磁场均匀度>95%的区域达到了在线圈径向-0.18～0.18m、轴向-0.17～0.17m之间,较课题组前期设计的Helmholtz线圈有了较大改进,为后续医学实验奠定了基础。     

2.5 MW 直驱风力发电机定子线圈绝缘性能研究

通过对2.5 MW直驱风力发电机定子线圈全套绝缘性能研究分析的介绍,系统评估了该机型定子线圈绝缘材料及绝缘结构。结果表明,定子线圈常规绝缘性能及在高频和工频电源下的耐电老化寿命均能满足行业标准及机组长期安全运行的需要。     

6kV级交流定子线圈主绝缘引入有机薄膜的研究

根据国内外高压电机定子线圈主绝缘中引入有机薄膜的情况,进行了大量的工艺探索,并作了2次电热老化试验,从试验结果中证明,高压定子线圈中引入薄膜是完全可能的.     

Quiet MRI with novel acoustic noise reduction.

Fast scan techniques, which are used to reduce scanning times, have raised scanning noise levels in magnetic resonance imaging (MRI) systems, resulting in greater patient discomfort and stress. It is well known that this noise is caused by vibration of the gradient coil due to the Lorentz forces generated by the current in the gradient coil, which is placed in a static magnetic field. We have confirmed that MRI noise can be substantially reduced by sealing the gradient coil in a vacuum chamber to block airborne vibration propagation, by supporting the gradient coil independently to block solid vibration propagation and by decreasing the eddy currents induced in RF coils, the RF shield and the static-field-magnet cryostat. Based on these findings, we have developed a silent MRI system in which scanning noise is markedly reduced under a wide range of scanning conditions.     

高压电机线圈绝缘结构及工艺的发展方向浅析

重点对大中型高压电动机的绝缘结构及工艺进行论述,提出应该重点探讨的若干方向,建议各厂应根据各自不同的情况,发展各自独特的绝缘结构和工艺。     

胶囊内窥镜新型外磁场驱动系统模型与仿真

为了克服传统推进式和被动式内窥镜在医用检查时存在的不足,提出了一种由三个同轴圆线圈和两对平行鞍线圈组成的胶囊内窥镜新型外磁场驱动模型。胶囊内窥镜内部嵌入NdFeB永磁体,通过控制外部线圈的电流来驱动永磁体,带动内窥镜在体内运动。在实验过程中,运用ANSOFT电磁场仿真软件分别对三个同轴圆线圈和鞍线圈的磁场分布进行了分析,结果表明,该模块能够产生三维匀强磁场,符合驱动无线胶囊内窥镜在体内运动的要求,并且结构简单紧凑,可控性高,有利于提高检测效率。     

Acoustic noise reduction in a 4 T MRI scanner.

High-field, high-speed magnetic resonance imaging (MRI) can generate high levels of noise. There is ongoing concern in the medical and imaging research communities regarding the detrimental effects of high acoustic levels on auditory function, patient anxiety, verbal communication between patients and health care workers and ultimately MR image quality. In order to effectively suppress the noise levels inside MRI scanners, the sound field needs to be accurately measured and characterized. This paper presents the results of measurements of the sound radiation from a gradient coil cylinder within a 4 T MRI scanner under a variety of conditions. These measurement results show: (1) that noise levels can be significantly reduced through the use of an appropriately designed passive acoustic liner; and (2) the true noise levels that are experienced by patients during echo planar imaging.     

软磁材料磁滞回线在线检测系统

介绍了基于PIC16F877A单片机的软磁材料磁滞回线的基本原理和软硬件设计。为了能方便地放置和更换试件,设计了线圈结构。该线圈结构由一个激励线圈和检测线圈组成,激励线圈套在检测线圈的外面,检测线圈采用完全对称的双线圈反向连接,可降低外部干扰。同时利用计算机进行数据处理,操作简单。测试表明,该系统可靠、简单、易于实现且工作性能稳定、测量精度高,有利地解决了软磁材料磁性参数的在线测试。     

金属探测器的平衡式线圈最佳空间位置研究

针对金属探测器的平衡式线圈设计时空间位置安排缺少理论的现状,介绍了一种平衡式线圈空间位置安排的计算方法。由平衡式线圈的结构,详细推导了金属异物通过线圈时的感应电动势大小,并采用MATLAB进行结果仿真,得出了激励线圈与接收线圈的最佳空间摆放位置及金属通过平衡式线圈的最佳探测点。最后通过实验验证了该计算方法的合理性,为平衡式线圈的制作提供了理论依据。     

110 kV铝绕组变压器增容改造方案和经济技术比较

通过对铝绕组变压器的分析，阐述了对其进行改造的必要性和可行性，对改造的具体方案进行了技术论证和经济技术比较，首次提出了一种铝绕组变压器改造新方案，并提出了改造的技术条件和技术措施。     

低压断路器合闸线圈保护的研究

提出一种解决低压合闸线圈烧毁的方案,结合具体要求设计出一种针对低压合闸线圈保护电路。在合闸线圈回路中增加了一个保护装置,当断路器未能及时跳闸时,采用4060芯片延时启动保护,切断合闸线圈回路,从而保护合闸线圈。低压合闸线圈回路在正常工作时能够监视低压主电路的运行状态,在发生短路故障时,能够切断合闸线圈保护回路,避免合闸线圈长时间工作在大电流环境下而烧毁,避免断路器操作机构卡死或者断路器辅助触点切换不正常,导致合闸线圈回路不能及时断开而烧毁的现象发生。     

雷电流传感器罗氏线圈的研制及测试

基于罗氏线圈的理论分析,结合线圈安装位置的限制,设计了雷电流传感器罗氏线圈,进行了仿真验证和性能测试。结果为：仿真显示所设计罗氏线圈能够达到自积分线圈的要求;性能测试显示所研发的罗氏线圈测量雷电流的准确度和线性度均比较好,可满足雷电参数测量的要求。     

基于ANSOFT的含气隙铁心线圈电感分析

针对铁心线圈电感非线性问题,利用ansoft有限元分析软件,分析了铁心对线圈电感的影响.研究结果表明:铁心会大大增加线圈的电感,但随着励磁电流的增加线圈的电感会先增加后减小;当铁心内部含气隙时,气隙的位置和大小都会影响电感的变化率.     

高压电机操作过电压及其匝间绝缘

以单导体架空线传播方式或单支路与地组成Ｌ／Ｋ－Ｃ链路方式，以及多导体多支路网络传输方式分析研究了高压电机多匝线圈定子绕组的操作过电压，匝间过电压，并推荐了合理选择匝间绝缘的方法。     

双面对称布线印制电路板型Rogowski线圈

印制电路板(PCB)型Rogowski线圈广泛用作复杂电磁环境下的电流测量传感头,其性能决定着电流测量的灵敏性和精确度。针对传统直连结构PCB型Rogowski线圈的不足,设计了一种双面对称布线PCB型Ro-gowski线圈,在PCB板双面均匀密布沿半径方向且两端带导孔的直连铜箔,通过外径导孔处小段圆弧连接布线铜箔呈对称结构,使得线圈结构对称且单匝线圈垂直于PCB板面并指向轴心;在输出端设置与绕线方向相反的回线以抵消垂直PCB平面的杂散磁场干扰。计算了线圈的电磁参数,研究了被测载流导线偏离线圈轴线及线圈外存在干扰电流时线圈与被测载流导体间的互感特性并测试了其互感值。实验测试结果与理论计算值相符,表明该PCB型Rogowski线圈一致性好,抗干扰性能强,适合于用作外界杂散磁场复杂情况下的电流测量传感头。     

Magnetic resonance imaging of the female pelvic floor and urethra: body coil versus endovaginal coil

The anatomy of the female pelvic floor and urethra is complex. With the introduction of MRI, the discussion about the normal anatomy of this area has not diminished. The use of a body coil may be contributary to this. In the present study images obtained with an endovaginal coil are compared with those of a quadrature body coil series to study the possible advantages of endovaginal imaging. Axial and radial T₂-w TSE images at a 1.0-T machine were obtained in seven healthy volunteers. The pelvic floor structures as well as the levator ani muscle and the urogenital diaphragm are excellently demonstrated with the endovaginal coil. Also, the urethrovaginal sphincter could be recognized in six volunteers, but only in three with the body coil. In six volunteers a new ligamentous structure, the urethropelvic sling, connecting the urethra to the levator ani muscle and contributing to the supporting mechanism of the urethra is shown with the endovaginal coil. The zonal anatomy of the urethra is excellently shown with the endovaginal coil. The urethral length could only be accurately measured with this coil and ranged from 3.1 to 3.6 cm. Compared with the body coil, endovaginal MRI is excellent in demonstrating the anatomy of the pelvic floor and urethra.     

放电线圈和电压互感器的对比

对照电压互感器的原理和特点,分析了单相电磁式高压并联电容器专用放电线圈与电压互感器的相同点和差异,并对放电线圈主要特点进行了阐述。结合放电线圈的特点,对放电线圈的选用和试验研究提出一些建议。     

电磁发射拦截系统发射线圈三维温度场数值计算

为了更好地对电磁发射拦截系统的发射装置进行设计和实验研究,分析了发射装置的工作原理,建立了发射瞬间发射线圈温度场的数学模型。用有限元软件编制仿真程序建立了发射装置的仿真模型,并对其进行了三维温度场的有限元仿真,得到了发射线圈的温度随时间变化的规律;分析了线圈电流峰值载荷变化对线圈温度的影响规律。结果表明:由于发射线圈中脉冲电流产生焦耳热的作用,线圈的温度瞬时升高,但加载过程的前段时期内线圈的温度分布很不均匀,最高温度位于最里圈的内侧,随着放电时间的延长,由于受到热传导的作用,线圈的温度逐渐下降并趋于均匀;发射线圈的温度随着电流载荷峰值的增大而迅速升高,若温度过高,会影响发射装置的发射效率和使用寿命。故当发射线圈的电流载荷较大时,应采用必要的冷却措施,以减少发射线圈的温升。     

Stripline resonator and preamplifier for preclinical magnetic resonance imaging at 4.7 T

Object

To design and evaluate a fully shielded, ??/4 stripline resonator as a receive-only surface coil for preclinical MRI at 4.7 T.

Materials and methods

A 20 mm diameter stripline surface coil was fabricated from double-sided Duroid 5880 PCB material and was directly coupled to the input of a MOSFET preamplifier, without requiring a matching network. The new coil was compared with a conventional 20 mm, wire loop, receive-only surface coil in imaging experiments with a separate transmit-only saddle coil.

Results

The stripline surface coil exhibits a loaded Q-factor of 132 at 200 MHz, compared to 138 for a conventional wire loop coil and its resonant frequency drops by 0.2 MHz under loading, rather than 0.5 MHz for the wire loop. The stripline coil displays a more symmetrical B ₁ map compared to the wire loop, but the SNR falls off more rapidly with depth so it is 30% poorer 8 mm from the coil plane. It should be possible, however, to reduce this difference by using a thicker dielectric in future versions of the stripline coil.

Conclusion

Compared to a conventional surface coil, the stripline coil is easy to manufacture, requires shorter set-up times and shows reduced dielectric interaction with conductive samples.     

高速永磁同步电机线圈与绕组电枢磁场计算方法及其内在联系

为简化和统一复杂绕组磁场的分析问题,提出一种简易的单匝线圈磁场预测绕组磁场计算方法。基于高速永磁同步电机等效同心圆多层模型和涡流场泊松方程,结合各种介质交界面条件和边界条件,建立了稀疏矩阵形式的单匝线圈电枢磁场的解析方程组。从绕组排布组合形式多样性的特点出发,根据线圈位置和同相线圈连接方式,通过线圈代数化和绕组集合化处理,将线圈和绕组之间的递推关系简化和统一,揭示其关联性。线圈和绕组电枢磁场的解析计算方法和内部关系得到有限元仿真和相关文献计算方法的证实,结果表明了使用单匝线圈磁场研究绕组磁场问题的准确性和可行性。最后基于相关计算方法和内部关系的研究,分析了绕组合成磁场时空谐波的规律。