Long and short duration pulse performance of zinc oxide varistor compacted with modified pressing cycle
Zinc oxide varistor blocks are commonly pressed by the double action uniaxial compaction technique. The pressing cycle, similar to that followed in the case of conventional ceramic processing, composes of applying a load on the varistor powder (filled in the die by a suitable filling mechanism), a...
| Main Authors: | , , , |
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| Format: | Conference or Workshop Item |
| Language: | English |
| Published: |
1996
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/26855/ http://irep.iium.edu.my/26855/1/Press_cycle_%2302.pdf |
| Summary: | Zinc oxide varistor blocks are commonly pressed by the double action uniaxial compaction technique. The
pressing cycle, similar to that followed in the case of conventional ceramic processing, composes of
applying a load on the varistor powder (filled in the die by a suitable filling mechanism), accompanied by
holding or dwell time at different phases of loading. This holding time in the form of pre-press dwell. press
dwell and ejection delay are maintained respectively atlow pressure, at peak pressure and at no pressure
prior to ejection. The dwell allows the material under compaction to rearrange and expels the trapped air or
gas, thereby helping to reduce the inter and intra-particle pores. Thus this enhanced property of the green
body is secured with the aim of attaining improved sintered properties of the ceramic. The present study
which uses two level factorial design to assess the effect of dwell reveals that improvement in varistor
performance is not achieved by randomly increasing the duraLion of dwell. Rather the varistor properties are
found to be influenced by the individual as well as the interactive effects of the variables leaving scope for
optimization, The investigation consisted of testing the energy absorption capability of varistors injected by
a long duration pulse. and the high current performance of those subjected to a short duration pulse. |
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