A few aspects concerning a new varistor material for low and medium voltage surge arresters

ZnO varistors are essentially ceramic poly-crystalline n - semiconductors. They are applied in making all type of surge-arresters due to some important advantages such as: a high level of non-linearity for the current-voltage characteristic, a high energy absorption capacity and an excellent response time (less then 100 ns), which make them useful for protecting other sensible electronic devices. This paper presents a new manufacturing technology for ZnO based varistors and a new mixture of oxides used in order to obtain a new material with non-linear electric properties. The oxides involved are Cr₂O₃ and MnO₂ as additives. This varistor material has a smaller electrical capacity, suitable even for telecommunication applications. The new technology is simply to apply by any manufacturer. Started from chemical measurements, and finished by electrical tests, the experimental part of this paper is an Interdisciplinary research. A new and simple method of testing the electric capacity of a certain varistor is presented, based on the oscilloscope measurements at various frequencies.