• Ashok Kumar Shukla

Mica is essential for high voltage (>3 kV) insulation that demands corona resistance. The mineral mica, Muscovite and Phlogopite types, abundantly available in flake form has very limited application due to its rigid and brittle nature. However, owing to its split ability into micro thin flakes, mica is processed into reconstituted mica in paper form and converted into a flexible composite material (folium and tapes) by reinforcement with glass (E grade) fabric or polyimide film bonded with a synthetic thermosetting resin (namely, Epoxy or Silicone) in B-stage to enable its application in conductor and main coil insulation in high voltage rotating machines such as motors and generators. The article overviews the characterisation of the reconstituted mica papers and their composites that include dielectric strength, dissipation factor (Tan δ), permittivity (ε), and partial discharge (p. d./corona) behaviour under thermal and high voltage endurance. Important features of application of advanced mica-composites using the conventional resin-rich technology vis-a-vis state-of-the-art VPI (vacuum pressure impregnation) technology currently employed in the manufacture of HV rotating machines have been discussed. VPI technology leads to a void-free insulation with incorporation of maximum mica content (up to 65-70%) resulting in the better performance in terms of lower dielectric losses and partial discharges under prolonged thermal and electrical stresses.

Mica, insulation, electrical, high voltage, polymer

"Advanced Mica-Polymer Composites for High Voltage Insulation - An unique & essential material", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.6, Issue 5, page no.386-390, May-2019, Available :http://www.jetir.org/papers/JETIRCD06067.pdf

"Advanced Mica-Polymer Composites for High Voltage Insulation - An unique & essential material", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.6, Issue 5, page no. pp386-390, May-2019, Available at : http://www.jetir.org/papers/JETIRCD06067.pdf