While series BWF is made for the widest range of applications, parameter of CRF-series are designed for circuits with clearly defined failure-mode-conditions, especially in power-supplies and chargers for mobile equipment.
Resistors of CRF-series will fuse abruptly, without flames or explosion, when mains-voltage (230 Vrms) is applied. Adaptation to such applications allows some compromises for production-technology and with that, a different cost-structure.
Resistive wire is wound onto a capped ceramic element and welded to the end-caps.
A special varnish is used to absorb metal-vapour, appearing when the resistive wire fuses under overload, to safely avoid arcing and short-circuit.
For resistance values from 10R to 330R (100R for size 251-4) resistive wires are designed to evaporate at mains-voltage. Finally, resistor-elements are conformally coated with silicone-varnish which protects but does not electrically insulate the device.
Non-inflammation is secured for resistance-values below 10R and also for other voltages, but fusing-versus-time-function must be tested in the application.
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printed at
03.10, 2010.