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PPTC resettable fuse Thermal expansion and contraction characteristics

文章出处:fuse factory Author:Yaxun Electronics Popularity: Time:2017-03-05 18:19 【Big Middle Small
PPTC resettable fuse Thermal expansion and contraction characteristics
    PPTC resettable fuse work is characterized by:Since the recovery of the fuse in the normal working environment,The polymeric resin tightly binds the conductive particles to the crystalline structure,Constitute a chain-like conductive path,At this time PPTC low resistance state (a),The volume is also in the normal state.
      When the line occurs short circuit or overload,The heat generated by the high current flowing through the PPTC resettable fuse melts the polymer,PPTC rapid expansion of volume,Forming a high resistance state (b),Through the PPTC resettable fuse current quickly reduced,Thus limiting and protecting the circuit.When troubleshooting,Self-recovery fuse re-cooling crystallization, volume shrinkage,Conductive particles re-formed conductive path,PPTC resettable fuse to return to low resistance state,Thus completing the protection of the circuit
Because the product needs to deal with thermal expansion and contraction process,We need special treatment of epoxy resin packaging process.Yaxun electronic selection of modified epoxy resin for polyethylene self-recovery fuse packaging materials.And the effect of encapsulation on the thermal characteristics of the fuse was studied.The encapsulation layer affects the heat dissipation capacity of the core material.When the current is large enough.The package has little effect on the operation time of the fuse.  Polarized conductive composites often have a positive temperature coefficient (PTC) effect.That is, the resistivity of the material increases with increasing temperature.And rapidly increases near the melting point of the polymer.With thermal switch characteristics.The material can be used for the preparation of circuit protection elements.
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PPTC resettable fuse

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