Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once ignited, substantially reduce its working life.This paper attempts to investigate tracking/erosion performance of room temperature vulcanized (RTV) silicone rubber along with flame retardant parameters using aluminum trihydrate (ATH), graphene nanosheets (GN) and milled glass fiber (GF) additives.The inclined plane test (IPT) was performed in line with criteria defined in IEC 60587 using step-up tracking voltage method while flame retardancy is evaluated according to ASTM E 1354.0 using a cone calorimeter.Results suggest 30% of ATH assists in improving physical tracking/erosion resistance of pristine silicone elastomer rubber by impeding development of leakage current and a great reduction in maximum average temperatures on the surface of RTV2.Further improvement in performance of RTV2 is achieved through introduction of 1% of GN and 5% of GF as seen in RTV4.Moreover, 30% of ATH reduces heat release rate and smoke production rate, and this trend is improved with the introduction of GN/GF.RTV4 has pop up as the most promising silicone rubber composite with excellent electrical tracking, erosion, and flame resistance performance relative to its counterparts in this study.
Abstract Variation in air pressure severely affects the insulation of electric vehicle (EV) motors, hence weakening the reliability of EVs for safe operation. Nomex‐polyimide‐Nomex, a typical insulation material for EV motors, was used to investigate the motor insulation performance under different air pressures. The results show that the partial discharge inception voltage is significantly reduced for EV motors operated at lower air pressures, and the probability of partial discharge (PD) occurrence is increased. The macroscopic results reveal that the active area of the PD expands at low pressure, while the non‐corroded ring appears in the centre. Additionally, although the number and amplitude of the PD increase significantly with decrease in air pressure, the active area of the PD expands and electrical stress on the insulation per unit area increases slowly. Therefore, when the pressure decreased from 60 to 40 kPa, the endurance life does not show a significant downward trend. Furthermore, the dielectric constant and loss of the low‐pressure samples significantly change during the ageing process, which further indicates critical degradation of the insulation. The aforementioned investigations reveal that the air pressure at different altitudes has a significant impact on the performance of insulation materials.
Measurements of space charge density and trap levels are informative ways to predict failure conditions of insulation materials. The charges are injected from electrodes and penetrate from surface towards deep inside of the insulation material. In order to resist the charge injection, trapping, migration and increase charge recombination, de-trapping and extraction rate, layer (nanocomposite-PI-nanocomposite) sandwich structure samples are used. Two techniques Pulse Electro Acoustic (PEA) and Thermal Stimulated Current (TSC) are combined to characterize space charge behavior and trap levels. Lab-view based program is used to detect the charges density distribution and total charge decay, different peaks of current using TSC technique are used to get activation energy and trap level density. The effects of structural interface (single, double, three layers) and types of nano (Al 2 O 3 , SiO 2 ) fillers are analyzed to influence charge accumulation polarity and trap levels. Trap levels are calculated using TSC data as well as total charge decay data. The trap values calculated from both data match each other. Al 2 O 3 -PI-Al 2 O 3 sandwich structure showed remarkable improvements to resist accumulation of space charge for longer time. Mostly charges are shallow traps with 1.126eV trap level and recombination rate is higher. In double layer structure in which interface is made up of SiO 2 and Al 2 O 3 , deep trap level of 1.26 eV and higher trap density is observed. The charges decay is faster in three layer structure than double and single layer structure. It is concluded that the interface formed with different type of nano and structure of insulation, both are an important parameters for manufacturing industry to suppress space charges accumulation and traps.
Cost-effective, clean, highly transparent, and flexible as well as a coatable packaging material is envisioned to solve or at least mitigate quality preservation issues of organic materials, originating from moisture interaction under ambient conditions. Liquid phase processing of packaging coatings using nano-clay and polyvinyl alcohol (PVOH) has been developed and reported. Detailed analysis of the developed coating revealed moisture permeability of 2.8 × 10−2 g·cm/m2·day at 40 °C and 85% relative humidity (RH), which is in close accordance with Bharadwaj’s theoretical permeability model. Moreover, the developed coatings are not only more than 90% transparent, when exposed to white light, but also exhibit excellent flexibility and even after going through 10,000 bending cycles maintained the same blocking effect against moisture.
Global warming, depletion of fossil fuels and energy crisis has been the most debated and researched global challenges of the past few decades and more so from the beginning of the 21st century. One solution that apparently seems to answer our world's biggest challenges is the adoption and penetration of electric vehicles in both private and public transport. Though there has been a steady rise in the use of electric vehicles, yet the estimated targets of electric vehicles in the market share have failed to be met. At the current rate of adoption of EVs, it is not far-fetched to say that it might be too late to make an impact if rigorous efforts are not adopted to promote and incorporate EVs into the system. In this paper, we take a look at some of the issues that are largely preventing consumers from switching toward zero-emission cars.
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