Lightweight materials, such as polymers and composites, are increasingly used in the automotive and aerospace industries. Recently, there has been an increase in the use of these materials, especially in electric vehicles. However, these materials cannot shield sensitive electronics from electromagnetic interference (EMI). The current work investigates the EMI performance of these lightweight materials using an experimental setup based on the ASTM D4935-99 standard and EMI simulation using the ANSYS HFSS. This work studies how metal coating from zinc and aluminum bronze can improve the shielding performance of polymer-based materials, such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), and polyphthalamide (PPA). Based on the findings of this study, a thin coating (50 μm) of Zn on the surface of PPS and a thin coating of 5 μm and 10 μm of Al-Bronze, respectively, on the surface of PEEK and PPA have indicated an increase in the shielding effectiveness (SE) when subjected to EMI. The shielding effectiveness significantly increased from 7 dB for the uncoated polymer to approximately 40 dB at low frequencies and up to approximately 60 dB at high frequencies for coated polymers. Finally, various approaches are recommended for improving the SE of polymeric materials under the influence of EMI.

Polypropylene has been used in radio-frequency capacitors and has also started to be employed in cables as insulation. The objective of this study was to evaluate the electrical properties of polypropylene filled with natural clay as a nano-material. Polypropylene samples having 0%, 2% and 6% natural clay by weight were exposed to 60-Hz sinusoidal voltages at two different rates of rise. The breakdown voltage of each sample was recorded at these different ramp rates. Also, the Root-mean-squared (rms) current was measured as the voltage was increased across the test samples. The important findings of this study were (a) the breakdown strength of the natural nanoclay-filled polypropylene was higher than the unfilled polypropylene, and the optimum concentration of nanoclay appeared to be 2% by weight; (b) the current density as a function of the electric-field intensity indicated a non-linear behavior with saturation, and the saturation onset took place at a higher electric-field intensity in nanoclay-filled polypropylene, wherein 2% nanoclay seemed to be the optimum concentration as well for the onset electric field of saturation.

The corona-generated audible noise (AN) has become one of decisive factors in the design of high voltage direct current (HVDC) transmission lines. The AN from transmission lines can be attributed to sound pressure pulses which are generated by the multiple corona sources formed on the conductor, i.e., transmission lines. In this paper, a detailed time-domain characteristics of the sound pressure pulses, which are generated by the DC corona discharges formed over the surfaces of a stranded conductors, are investigated systematically in a laboratory settings using a corona cage structure. The amplitude of sound pressure pulse and its time intervals are extracted by observing a direct correlation between corona current pulses and corona-generated sound pressure pulses. Based on the statistical characteristics, a stochastic model is presented for simulating the sound pressure pulses due to DC corona discharges occurring on conductors. The proposed stochastic model is validated by comparing the calculated and measured A-weighted sound pressure level (SPL). The proposed model is then used to analyze the influence of the pulse amplitudes and pulse rate on the SPL. Furthermore, a mathematical relationship is found between the SPL and conductor diameter, electric field, and radial distance.

The limiting equivalent electric fields in N/sub 2/+SF/sub 6/ binary gas mixtures due to Townsend discharges are evaluated directly from a Monte-Carlo simulation when the mixture is subjected to orthogonal electric and magnetic fields. Along with the limiting equivalent electric fields, transverse and perpendicular drift velocities, electron mean energies and collision frequencies are also determined within the scope of the Monte-Carlo simulation. The equivalent reduced electric field (EREF) concept for the corresponding limiting electric fields is also investigated for the calculated mean energy levels and collision frequencies. The EREF values are found to be in good agreement with the previously published limiting electric field data.

Nano-size particles affect in a great way dielectric and mechanical properties of polyurethanes. In order to find out characterization its effects on solid insulators, many of different nanoparticles have been investigated by experts and scientist. The objective of this study was to investigate the dielectric properties of mica-filled thermoplastic polyurethane (TPU). Nanometer and micrometer-size mica fillers with various mixing ratios were doped into TPU. The particle size of mica fillers used in this study was 1 nm, 10 nm and 5 μm. To investigate the change in dielectric properties, relative permittivity, loss factor, dc conductivity and breakdown strength of thermoplastic polyurethane composites filled with mica fillers is evaluated. The loss factor of the composite, on the other hand, was the lowest with 3% mica content for 1 nm particle size, 2 % mica content for 10 nm particle size and 1 % mica content for 5 μm particle size. The micron size mica added samples measured breakdown voltages were at least 2,5 time higher than the pure TPU. Physical changes due to addition of nano size mica particles are observed by using Scanning Electron Microscopy (SEM) analysis. Based on the results of the dielectric evaluation, it was determined that the optimum concentration for the composite is 1% by weight with a particle size of 5 μm.

In this paper, spectral characteristics of the corona-generated audible noise (AN) on a dc conductor are studied through a quadrate corona cage structure. To reduce the influence of background noise, all experiments are conducted in a semi-anechoic chamber. Different from previous investigations, time-domain waveforms of corona-generated AN are recorded and the frequency spectra are calculated based on the time-domain waveforms through the calculation method of A-weighted sound pressure level (SPL). The results confirm that the frequency spectra describe different characteristics at different applied voltages and have a close relationship with pulse amplitude and pulse repetition frequency. In addition, the AN from a negative corona discharge contains more high-frequency components than those from a positive corona discharge. The components with the frequency above 400 Hz contribute most to the resultant total A-weighted SPL. The differences of AN from positive and negative corona discharges are interpreted on the basis of the corona discharge physics. Furthermore, some correlation frequency components in the frequency spectrum are found and can be used to calculate the total A-weighted SPL by adding correction values. Finally, the influences of pulse amplitudes and repetition frequency on the frequency spectrum of AN are discussed on the basis of the time-domain stochastic model.