Varistors with improved radial resistance distribution - comprises differing ceramic compsn. for centre and mantle for cylinder for high energy dissipation

摘要

Varistors prepn. comprises dividing cylindrical form into 2 coaxial parts, using ceramic mass of one compsn. for the inner core and using a mass with a different compsn., contg. pref. a different amt. of Bi2O3, SiO2 or Sb2O3 for the outer mantle, sintering and coating part with electrodes. Mfr. pref. comprises using cylindrical press-form in which 2 coaxial compartments have been formed. Pref. compsn. of the ceramic mass in the outer mantle, compared with that of the inner core is: Bi2O3 0.5-0.75 times, SiO2 or Sb2O3 2-1.1. The radius of the core is pref. at least 70% of that of the complete part. USE/ADVANTAGE - Using outer mantle of a freely selectable width with a clearly defined compsn. The change in the concn. of Bi, Si or Sb-oxide reduce grain growth in the mantle and so a higher resistance, reducing the occurrence of fused channels due to high energy dissipation. Higher energy dissipation.