Resettable fuse
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A resettable fuse or polymeric positive temperature coefficient device (PPTC) is a
Operation
A polymeric PTC device is made up of a non-conductive
When power is removed, the heating due to the leakage current will stop and the PPTC device will cool. As the device cools, it regains its original crystalline structure and returns to a low resistance state where it can hold the current as specified for the device.[6] This cooling usually takes a few seconds, though a tripped device will retain a slightly higher resistance for hours, unless the power in it is weaker, or has been often used, slowly approaching the initial resistance value. The resetting will often not take place even if the fault alone has been removed with the power still flowing as the operating current may be above the holding current of the PPTC. The device may not return to its original resistance value; it will most likely stabilize at a significantly higher resistance (up to 4 times initial value). It could take hours, days, weeks or even years for the device to return to a resistance value similar to its original value, if at all.[8]
A PPTC device has a current rating and a voltage rating.[9]
Applications
These devices are often used in computer power supplies, largely due to the
See also
- Positive temperature coefficient
References
- ^ U.S. Patent 2258958.: "Conductive device", filed 13 Jul 1939, retrieved 7 mar 2017.
- ISBN 978-0-470-07369-8.
- ISBN 978-0-08-045556-3.
- ISBN 978-1-118-08258-4.
- ISBN 978-0-86341-399-5.
- ^ a b Institute of Electrical and Electronics Engineers. San Francisco Bay Area Council (1995). WESCON Conference Record. Western Electronic Show and Convention.
- ^ Machine Design. Penton/IPC. 1997.
- ^ "PolySwitch Resettable Devices Fundamentals" (PDF). TE Connectivity. Archived from the original (PDF) on 22 January 2015. Retrieved 31 August 2014.
- ISBN 978-3-642-18139-9.
- ^ Loudspeaker application note