The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This work describes an investigation about the influence of two service parameter on the PD inception voltage threshold of type I random wire wound stator insulation; the temperature and the voltage gradient (i.e. the rise time). An experimental campaign of PD inception tests was carried out on twisted pair specimens applying unipolar voltage pulses having different rise time. The results have been...
Considering the great importance of the degradation phenomena acting on the insulating materials of the inductor motor windings supplied by inverter drives based on IGBT the behaviour of different kinds of insulating organic enamels have been investigated. During the research activity, twisted pair specimens have been realized and subjected to severe voltage waveforms having peak to peak amplitudes...
Partial discharge (PD) endurance test was performed on twisted pair specimens of enameled wires consisting of polyamide-imide resin with nanometer-size fillers. Specimens were prepared with containing nanometer-scale silica or titania fillers, as well as specimens without fillers. In the PD endurance test, so-called V-t characteristics of the twisted pair specimen were measured by applying a constant...
Low voltage stator windings of electrical machines are often realized by means of wires insulated by organic enamel. This kind of enamel can be subjected to partial discharges (PD) activity that could lead to breakdown condition the electrical insulating system so that the life time could be shorter than the expected one. In this research work, twisted pair specimens insulated by non corona resistant...
Summary form only given. Dental restoration interfaces can present failures, known as marginal microleakage. These failures are extremely difficult to diagnose and can develop into recurrent caries if left untreated. The most common tool used for diagnostic imaging in dentistry, X-ray, is not able to visualize micrometric structures. Evaluation of dental restoration in a non-invasive way is a very...
In this work the partial discharge (PD) patterns acquired during electrical aging tests performed on twisted pair specimens prepared by winding wires having conventional or nanostructured enamel insulation are compared. The conventional enamel is polyamide imide, while the nanostructured enamel is a polyamide-silica nanocomposite. The tests have been performed applying sinusoidal voltage at different...
This paper concerns the outcome of a life test campaign performed on twisted pairs specimens insulated by non corona resistant polyamide-imide enamel. Twisted pairs have been subjected to AC voltage having 50 Hz frequency: different voltage amplitude levels higher than the partial discharge inception voltage (PDIV) have been considered. The tests have been performed into an environmental chamber in...
This work concerns the comparison between the behaviour of winding wires insulated by a conventional organic enamel or by a nanocomposite enamel, when subjected to the action of surface partial discharges. Some aging tests were carried out applying a 1500 Hz sinusoidal voltage with different amplitudes. The outcome was summarized through lifetime plots. During the tests, partial discharges (PD) patterns...
Polymeric nanocomposite materials have shown a big potential for an impact in wire wound rotating machine stator insulation. Small wire wound machines, in fact, have a mainly organic stator winding insulation which is easily degraded by partial discharge (PD) activity. In this kind of equipment, then, the presence of PD activity leads to failure in a very short time. Nanofilled polymeric materials,...
This paper discusses the partial discharge (PD) resistant mechanism of nanocomposite enamel wires under repetitive surge voltage condition for inverter-fed motors. We focused on the reduction of deterioration depth and the surface condition of nanocomposite enamel wires after repetitive surge voltage application with successive PD. Experimental results revealed that the longer lifetime of breakdown...
Nanocomposite enameled wires have been developed for inverter-fed random wound motor windings, however, partial discharge (PD) characteristics is still underlying physics. In this study, effects of environmental conditions on PD characteristics in twisted pairs with conventional and nanocomposite enameled magnet wires were investigated. Measurements of the PD inception voltage (PDIV) and an amount...
It is well known that organic enamels commonly used for the insulation of the wires used in the windings of low voltage electrical machines can suffer premature failures due to the degradation induced by partial discharges (PD) activity. Nanocomposite polymers can represent an innovative and powerful solution to this problem as they can provide an enhanced resistance to the action of PDs at a competitive...
The aim of our investigation was definition of the high technology directions of processing and recycling of ash waste and slags of thermal power stations. As a result of research compoundings of preparation are developed and experimental samples of ceramics (including porous ceramics), protectively-decorative coverings, glazes, enamels and engobes, porous ceramics, refractories, facing tiles are...
In this research work, the performance of enamelled wires with and without nanofiller in the coating is investigated. The wire specimens are exposed to PWM-VSC waveforms. After partial discharge erosion (PD) on enamel wire coatings, the surface roughness is measured by using image-tod software. In all investigations, the images used, are captured by using scanning electron microscope (SEM). The experimental...
Due to a power density increase, the thermal stresses endured by the electrical insulation of rotating machines are also increasing. However, up to now, most of the characterization (breakdown voltage, permittivity, loss tangent) are carried out in a temperature range which rarely exceeds the thermal class. Consequently, there is a lack of knowledge on the behavior of these materials when they are...
Recently, partial discharge (PD)-resistant enameled wires mixed with inorganic particles of nanometer order, referred to as the nanocomposite enameled wires, have been developed and verified to have longer life compared with conventional enameled wires. We investigated the fundamental characteristics on PD inception, propagation and breakdown (BD) of nanocomposite enameled wire under surge voltage...
Spectrophotometric analysis of human enamel sections shows two near-IR wavelengths that are strongly absorbed and are potentially suitable for efficient generation of surface acoustic waves for dental non-destructive testing application.
The present work concerns the partial discharge (PD) activity in simple insulating system (twisted pairs) when switching voltage waveforms are applied. A special low frequency PD coupling system allowed to determine two quantities indicating the stress actually connected with the PD activity. Such parameters have been considered to determine life prediction models
The accelerated degradation under high frequency AC voltages of enameled wires that are nano-filled is compared to enameled wires without nano-fillers. The surface roughness and erosion depth of wire specimens, aged in the presence of partial discharge (PD), are studied using a scanning electron microscope (SEM). Changes in the chemical bonding behavior of wire insulation due to PD erosion, are also...
The ability to modify the resin backbones of wire enamels and impregnating resins is a powerful tool in studying the possible synergistic effects of these two insulations. The possibility to develop a unified system of the primary and secondary insulation resins yields the potential to develop the next generation of insulation families. Adhesive versus cohesive forces at work during the coating of...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.