First 240Vac surface-mount resettable fuse

First 240Vac surface-mount resettable fuse

Technology News |
By Nick Flaherty

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Bel Fuse, which celebrates its 75th anniversary this month, has launched industry’s only surface mount, PPTC resettable fuse, line-volt-rated to 240VAC.

Designed to protect against electrical overloads and short circuits, the Bel 0ZAF resettable fuse series provide circuit protection for a variety of applications in the IoT, industrial, and medical sectors. These fuses are crucial for use in safeguarding industrial controls, test and measurement equipment, robotics and safety systems.

The soldered surface mount 2920 package not only offers cost efficiency for PC mount assembly, but also accelerates design and production timelines by eliminating the need for through-hole mounting. Typical currents are 50mA to 160mA.

The PTC resettable fuse consists of a block of polymeric material containing conductive carbon granules which is sandwiched between two conductive metal plates.

When this polymer block reaches approximately 125C, either due to current passing through it via conductive chains of carbon particles or due to an external heat source; it swells volumetrically.

 This expansion breaks apart the majority of the chains of carbon granules that run randomly between the two conductive plates. This results in a sharp increase in resistance across the two plates which all but eliminates current flow through the device, allowing just enough residual current flow to maintain the block’s internal temperature at 125C.

Once this “tripped” state current is cut off, the polymer brick cools and shrinks to its original size, allowing the broken carbon chains to reestablish themselves and permit the part to return to its low resistance state.

Once cooled to ambient room temperature, the PTC will once again exhibit a resistance less than its “R1max” rating. At currents below the device IHOLD rating, AND at temperatures below 100C, the PTC maintains a resistance value below its R1 MAX rating.

The Bel 240V 0ZAF resettable fuse series is UL recognized components and IEC certified and are available from a variety of distributors.



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