Bel Fuse 0ZRN0200FF1E

Fundamentally, a Bel PTC consists of a block of polymeric material containing conductive filler, bonded between two conductive planar terminals. At currents below the device's I HOLD rating, and at temperatures below 100°C, the PTC maintains a resistance below its R1 MAX rating. As the device temperature approaches 130°C — whether due to elevated ambient temperature or current exceeding its I TRIP rating — volumetric expansion of the filled polymer disrupts most of the conductive paths formed between terminals by chain contacts of adjacent filler particles, causing device resistance to increase sharply by several orders of magnitude. At the higher "tripped" resistance, only sufficient leakage current is allowed to maintain internal heating that keeps the device "held" in its 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 restoring the device to its low-resistance state. The catalog data for each device specifies a "Typical Power" value. This is the power at 23°C at which a tripped device dissipates heat to its surroundings at exactly the rate required to maintain that 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 appearing 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. Consider the following example... A PTC with a Typical Power of 1 watt protecting a circuit powered by a 60V supply will exhibit an apparent tripped resistance "R" of: R = 60² / 1 = 3600 ohms. When that same tripped device is used to protect a 12V circuit, it will now present an apparent resistance of: R = 12² / 1 = 144 ohms. The Typical Power value is "typical" in that any physical factor affecting heat dissipation — such as ambient temperature or air convection — will to some degree alter the power level required for the PTC to maintain its internal temperature. In short, a PTC does not exhibit a constant, quantifiable tripped resistance value.

• Very Low resistance, ery High hold current, olid state, adial leaded product ideal fr upto 16V and Operating temperatures upto 125°C
• TUV (Std. EN60738-1-1, Cert.R50102187)
• UL Component (Std. UL1434, File E305051)
• UL Conditions of Acceptability:
  • These devices have been investigated for use in safety circuits and are suitable as a limiting device.
  • These devices have been calibrated to limit the current to 8 amps within 5 seconds, per ANSI/NFPA 70, “National Electrical Code".

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