Bel Fuse 0ZRP0300FF1A

At its most fundamental level, a Bel PTC consists of a mass of polymeric material containing conductive filler, bonded between two conductive planar terminals. At currents below the device's IHOLD rating, and at temperatures below 100°C, the PTC maintains its resistance below the R1 MAX rating. As the device temperature approaches 130°C — whether due to elevated ambient temperature or current exceeding its ITRIP rating — the volumetric expansion of the filled polymer disrupts most of the conductive paths formed by chain contacts between adjacent filler particles across the terminals, causing device resistance to increase sharply by several orders of magnitude. At this higher "tripped" resistance, only sufficient leakage current is permitted to sustain internal heating, keeping the device "latched" in the tripped state (approximately 125°C) until power is interrupted. Once power is removed, the PTC core cools and contracts, allowing the conductive chains to reform and returning the device to its low-resistance state. The catalog data for each device specifies a "typical power" value. This is the power required at 23°C for a tripped device to dissipate heat to the surrounding environment at exactly the rate needed to maintain the tripped state. By Ohm's Law, power can be expressed as: W = E² / R. Therefore, the approximate resistance of a "tripped" PTC can be determined by: R = E² / W, where "E" is the voltage across the PTC (typically the open-circuit voltage of the supply) and "W" is the typical power value for the specific PTC. Since the function of a PPTC is to maintain a constant internal temperature, its apparent resistance will vary with applied voltage and, to a lesser extent, with ambient conditions.

• Solid-state radial leaded product for applications up to 60VDC.
• Operating (hold current) range: 500mA - 5A, temperature range: -40°C to 85°C.

Various electronic devices