10-07-2010, 01:41 PM
A polymeric positive temperature coefficient device also known as polyfuse is a passive electronic component used to protect against overcurrent faults in electronic circuits.They come in many different commercial names like :
-PolySwitch
-OptiReset
-Everfuse
-Polyfuse
-Multifuse
Though non-linear thermistors they but after the current is removed, they come back to the conductive state. Thus they act like circuit breakers. Their major use is in computer power supplies, and also in aerospace/nuclear applications where replacement.
A PPTC device has a current rating. the PPTC device warms up above a threshold temperature when that limit is exceeded. The the electrical resistance of the PPTC device increases by several magnitudes making it like an open circuit thereby going to a tripped" state. The rated trip current can be anywhere from 20 mA to 100 A.
Composition:
It is made up of a a non-conductive crystalline organic polymer matrix , and also carbon black particles which makes it conductive. the polymer is in a crystalline state and carbon forced into the regions between crystals and carbon forced into the regions between crystals when the device is cool. In this state it pass a given current . the device will begin to heat when too much current exceeding the trip , the polymer will expand and the conducting state is reverted and it trips.
For more info refer these links:
http://en.wikipediawiki/Resettable_fuse
http://sharingmatrixfile/12036123/10-7.zip
-PolySwitch
-OptiReset
-Everfuse
-Polyfuse
-Multifuse
Though non-linear thermistors they but after the current is removed, they come back to the conductive state. Thus they act like circuit breakers. Their major use is in computer power supplies, and also in aerospace/nuclear applications where replacement.
A PPTC device has a current rating. the PPTC device warms up above a threshold temperature when that limit is exceeded. The the electrical resistance of the PPTC device increases by several magnitudes making it like an open circuit thereby going to a tripped" state. The rated trip current can be anywhere from 20 mA to 100 A.
Composition:
It is made up of a a non-conductive crystalline organic polymer matrix , and also carbon black particles which makes it conductive. the polymer is in a crystalline state and carbon forced into the regions between crystals and carbon forced into the regions between crystals when the device is cool. In this state it pass a given current . the device will begin to heat when too much current exceeding the trip , the polymer will expand and the conducting state is reverted and it trips.
For more info refer these links:
http://en.wikipediawiki/Resettable_fuse
http://sharingmatrixfile/12036123/10-7.zip
