Isovolta (Austria)

The ability of electrical insulating materials within a module to act as insulators is a key safety requirement for PV technology. Direct current breakdown voltage is therefore now specified for relied-upon insulator materials in the IEC 61730–1 safety standard. To fulfill that requirement, a new test method has been developed within the IEC TS 62788–2 backsheet standard for the measurement of breakdown voltage. The development of the test will be described, including the verification of the most critical parameters relative to factors such as defect population(s), dielectric medium, electrode size, electrode surface roughness, maximum current limit, moisture conditioning, number of replicate specimens, rate of voltage rise, specimen thickness, test polarity, and test temperature. Many of these parameters were specifically explored in discovery experiments as the test method was developed. An interlaboratory round-robin (R-R) experiment was conducted to further validate the test method by quantifying its repeatability and reproducibility. The materials examined in the R-R include the backsheet materials: polyethylene terephthalate (PET, two thicknesses), polyvinyl fluoride (PVF), and laminated PVF/PET/PVF (“TPT”) as well as the encapsulants poly(ethylene-co-vinyl acetate) (EVA), and polyvinyl butyral (PVB). The precision of the test method as well as key factors contributing to the measurement will be described.

Anhydride-curing of epoxy systems and application for electrical insulation has a history of 70 years [1]. For large generators and motors the most widely applied insulation system are mica-based insulation tapes that are impregnated with a mixture of Bisphenol-A-diglycidylether-type epoxy resins and methyl hexahydrophthalic anhydride (MHHPA).

Abstract New experimental results were collected for the free radical polymerization of styrene by pulsed laser polymerization in solution or in microemulsion. The location of the point of inflection (on the low molecular weight side) and the maximum of the first peak in the chromatograms (measured by size‐exclusion chromatography) was used to extract kp data. The extent of band broadening was determined with narrow polystyrene standards with an assumed Poisson chain length distribution. For a given experiment both kp values (obtained via the point of inflection and the maximum) were corrected and thus became identical in most cases. Even after the correction, the effect of chain length dependence persists to a higher chain length.

The possibility to increase operating performance and efficiency of an electric machine can be achieved through the improvement or modification of the components of the primary insulating material. Relevant variables in the construction of a machine can be found in the components of the insulating materials and their overall thickness. These components can influence the electric strength and overall service life. In addition, the electrical insulation system dictates the thermal classification and therefore the construction of a machine. It is understood that a thinner insulation exhibits a higher thermal conductivity than a comparable thicker one. By improving the thermal conductivity of the insulation through thickness reduction, it is possible to increase the current density in the conductors. However, with such a design change, the electrical strength and service life of the insulation remains an important consideration. An improvement in the thermal conductivity of a mica tape can be achieved through the addition of highly thermally conductive materials or by reducing the thickness of the carrier components. However, these alterations to a standard insulation often result in a decrease in the electrical and or the mechanical properties of the insulating material. In this paper, a new mica tape construction will be discussed. It will propose that it is possible to not only improve the mechanical and electrical properties of an insulating material, but to also reduce its overall thickness, while improving service life. The new development reduces the thickness of a standard insulating tape by 15%. With this achievement, both efficiency and power output of a machine design can be increased. Power calculations indicate that this increase is considered to be significant