Papers by Keyword: Dielectric Loss Tangent

Abstract: As the pumped storage stations played an important role in peak and frequency modulation, the reversible pump turbines were often subjected to rapid temperature transitions. In this research, considering the complexity operation condition of these kinds of motors, a novel thermal cycle aging platform was designed and the thermal cycling aging test was conducted on epoxy/mica insulation stator bars. Dielectric loss angle tangent (tanδ), capacitor (C), leakage current (I) and other electrical properties of stator bars were investigated at different aging time. The results showed that, tanδ and C of the stator bars increased with increasing aging time, while I (current) did not change significantly.

Abstract: The paper presents a comparative study of Ca_0.25Cu_0.75TiO₃ (CCTO) electrical properties produced by two methods - mechanochemical synthesis and high temperature treatment. Products differ significantly in terms of grain morphology and the degree of defects in structure. This is the reason why electrical properties are different.

Abstract: W-type hexagonal ferrite with composition BaCa₂Fe₁₆O₂₇ was prepared using a stearic acid gel method. The precipitate of barium calcium hexaferrite was calcinated at 650°C, 750°C, 850°C and 950°C in a furnace for 4 hours and then slowly cooled to room temperature. The dielectric constants (real Є and imaginary Є), conductivity (σ) and dielectric loss (tan δ) have been measured at room temperature as a function of frequency (10²-10⁶ Hz). The dielectric behavior of prepared hexaferrite samples can be explained by the mechanism of polarization and the electrical conduction mechanism is explained by using the electronic hopping model of Heike Johnson.

Abstract: The mechanical and thermal properties of hollow glass powder reinforced epoxy resin composites have been measured and evaluated in earlier studies. This basic but critical and important data have caused interests in the relevant industry in Australia. This study is therefore carried out to measure and evaluate the dielectric properties of the composites with a view to benefit the relevant industry. The relationship between the dielectric and thermal properties will also be studied and correlated. The original contributions of this paper are that samples post-cured in conventional ovens have higher electrical as well as mechanical loss tangent values than their counterparts cured in microwaves only. The storage modulus of all samples post-cured conventionally is higher than its counterpart. This is in line with the fact that they are softer material with lower glass transition temperatures. For all percentages by weight of glass powder, the glass transition temperature for the microwave cured sample was higher and the composite was stiffer; the opposite was true for the conventionally cured samples.