共查询到19条相似文献,搜索用时 125 毫秒
1.
2.
3.
为准确评价屏蔽材料在强电磁脉冲环境中的屏蔽效能,提出了一种基于屏蔽暗箱窗口法的材料电磁脉冲屏蔽效能时域测量方法。该方法将带有测试窗口的屏蔽箱体置于GTEM 室内,被测屏蔽材料安装在屏蔽箱的测试窗口上,利用置于腔体中心的单极子天线测量耦合进腔体的电磁脉冲电压波形,对测得的时域电压信号进行快速傅里叶变换( FFT) ,得到了被测材料频域屏蔽效能曲线。与频域测试结果进行了对比,结果基本一致。实验表明该测试系统可以有效减小局部增强效应对测量精度的影响,能够可靠评价强电磁脉冲作用下材料的屏蔽效能。 相似文献
4.
5.
屏蔽电缆转移阻抗和转移导纳的宽频测量 总被引:2,自引:0,他引:2
转移阻抗和转移导纳是表征外界电磁场对屏蔽电缆耦合机理的两个重要参量.基于传输线理论,提出了一种新的测量屏蔽电缆转移阻抗和转移导纳的简便方法.该方法既可以得到转移阻抗和转移导纳的幅频特性,又可以得到其相频特性,且测试系统比较简单.测试频率范围满足电力系统电磁兼容所关心的频段(0.1MHz~10MHz),对于更高频率屏蔽电缆转移阻抗和转移导纳的测量,可以通过选择更短的电缆样品来实现.为了验证测量方法的正确性,与现有方法的测量结果进行了对比.该测量方法可推广用于多芯屏蔽电缆的转移阻抗和转移导纳测量. 相似文献
6.
7.
8.
9.
为更好地评价电磁屏蔽材料对静电放电电磁脉冲的屏蔽效能,对静电放电脉冲激励下的材料的屏蔽效能进行了时域测试研究。以静电放电电磁脉冲为注入源,结合宽带同轴测试夹具和数字存储示波器,对一种平面材料的屏蔽效能进行了时域测试。通过得到的屏蔽前后的信号,计算了不同激励电压下该材料的峰值屏蔽效能,结果表明激励电压的大小对该材料的电磁脉冲屏蔽效能影响不大。通过对屏蔽前后信号的FFT 变换计算了其频域幅频特性曲线,与频域实验测试所得的幅频特性曲线进行了对比,结果比较一致。表明该时域测试系统能够可靠地评价材料对高压静电放电电磁脉冲激励下的衰减能力。 相似文献
10.
11.
Frequency- and time-domain expressions for the transfer impedance of single conductor shielded cables are proposed. The time-domain convolution needed for the evaluation of the distributed longitudinal voltage induced on the internal conductor of the cable is directly evaluated by means of an equivalent SPICE circuit that can be incorporated in already existing shielded coaxial cables circuit models. 相似文献
12.
Morriello A. Benson T.M. Duffy A.P. Cheng C.F. 《Electromagnetic Compatibility, IEEE Transactions on》1998,40(1):69-76
Theoretical models to compute the surface transfer impedance of cables often rely on simplifying assumptions. This, together with the fact that surface transfer impedance can vary considerably between cable samples of the same type, means that measurements become necessary. In this way an average performance may be determined. Many transfer impedance measurement methods have been proposed over the years and each has its own relative strengths. Two frequency-domain measurement methods are compared: the current probe method and the pull-on braid method. Both methods are inexpensive and can be set up very quickly without expensive cable preparation. Moreover, they operate over a broad frequency range with high accuracy. This is shown by the good agreement obtained between measurements carried out with the two methods 相似文献
13.
Measuring the coupling parameters of shielded cables 总被引:1,自引:0,他引:1
Methods for measuring the coupling parameters of shielded cables, transfer impedance, and transfer admittance are presented. In addition to a theoretical analysis, a simple easy-to-use low-cost measuring setup is shown. This setup permits the determination of modulus and phase of the coupling parameters. New measuring methods for the direct determination of the so-called optimizing factors, presented in an earlier paper (see ibid., vol.34, no.2, p.39-46, 1992) are also discussed. These methods are suitable for shielded cables and shielded cable harnesses as well 相似文献
14.
Judging the shielding effectiveness of shielded cables often means in practice that only the transfer impedance is considered. The transfer impedance essentially characterizes the coupling via the magnetic field; the coupling via the electric field, the transfer admittance, is mostly neglected. This may be correct for shields with high optical coverage but for optimized single braided shields (coverage ≈0.8 . . . 0.9), the transfer admittance has to be taken into account. In practice, the cable shields are mostly grounded or open-ended at the line ends. With regard to the shield connections, the electromagnetic coupling to a cable by a plane wave and coupling from a cable are investigated. From the results, optimizing factors for the coupling parameters of shielded cables are deduced. By means of these optimizing factors the coupling to and from a cable can be minimized in certain applications 相似文献
15.
16.
Primiani V.M. Moglie F. Pastore A.P. 《Electromagnetic Compatibility, IEEE Transactions on》2008,50(2):246-251
The paper considers the reverberation chamber (RC) method for the measurement of the shielding effectiveness (SE) of coaxial cables with braided shields. In particular, the voltage at the cable termination is numerically computed and compared to that measured in an RC. The RC field is represented by a finite summation of random plane waves, and a finite-difference time-domain (FDTD) code is used to calculate the outer shield current induced by the RC field. The knowledge of the shield current distribution allows the determination of the voltage at the cable termination's internal circuit after a proper numerical averaging. It is then compared to the measured voltage averaged over stirrer rotations. The method is applied to a commercially available cable model RG58, and using the nominal value for the transfer impedance of this cable type gives results in a satisfactory agreement with the measurements. Finally, the possibility of recovering the transfer impedance from the measured SE of the RC is discussed. 相似文献
17.
Jung L. Luiken ter Haseborg J. 《Electromagnetic Compatibility, IEEE Transactions on》1999,41(4):460-468
Besides the knowledge of the primary line parameters per unit length, the determination of the complex transfer impedances and transfer admittances of shielded multiconductor cables is the prerequisite for the calculation of the propagation of disturbing currents on the inner wires of the cable. With a measurement procedure based on triaxial measurement setups using multiconductor transmission line theory for evaluation, it is possible to determine individual transfer impedances and admittances for each inner conductor of a shielded multiconductor cable over a broad frequency range. This paper shows the measurement procedure, the method of evaluation: and from measurement results, the determination of the location and the calculation of the area of single-shield inhomogeneities by the evaluation of measured transfer impedances and transfer admittances 相似文献
18.
Buccella C. Feliziani M. Manzi G. 《Electromagnetic Compatibility, IEEE Transactions on》2004,46(4):597-605
An experimental procedure to detect and localize defects in shielded cables is presented. First, time-domain measurements are carried out by injecting a short rise time pulse in the input section of the shielded cable. Then, the clean algorithm is applied to the measurement results to identify possible damages in the cable line. The localization of the cable section with defects is finally obtained in a very simple way due to the adopted method of measurement in time domain using a ultrawide-band pulser with a very fast rise time. The proposed method is validated by detecting and localizing known defects purposely introduced in test cables. 相似文献
19.
An impulse current of several kiloamperes was injected to the shield of a shielded cable, which was terminated by a varistor. The induced voltage on the inner conductor caused by this impulse current reaches an amplitude in excess of the varistor's threshold level. The clamped voltage across the varistor and the injected current have been studied for different termination conditions of the shielding cable. Furthermore, this paper also presents the use of a lumped circuit to simulate the transfer impedance of an “electrically short” shielded cable in the time domain. In combination with the varistor circuit model, the shielded cable with the nonlinear load, a varistor, was also simulated straightforwardly in the time domain. Good agreement was found between the measured voltage and current oscillograms and the calculated waveforms. It is thereby demonstrated the validity of the developed lumped circuit model for the transfer impedance of a shielded cable 相似文献