Priority was given to the ability, to withstand and limit high rush-in current without fusing and, at the same time, to provide a fusing-characteristic for a wide load-range.
Inflammation must not appear at all and short-circuit must be avoided, also if the overload condition is repeated after fusing.

BWF-series complies with these requirements to the utmost possible extend and is therefore in use in safety-relevant applications for years.
Resistive wire is wound onto a fibreglass-core.

The resistive element is sub-assembled with a special varnish to protect from inflammation
The winding-parameter are chosen to ensure safe reproducibility of “fusing-time versus load” characteristics, what is significantly different from fusible film-resistors, which allow wide tolerances for their fuse-characteristics.

The resistive element is sub-assembled with caps and terminal-wires and conformally coated with a special varnish to protect from inflammation. The sub-assembly then is moulded in "bakelite"-resin.

Being kind of a heat-sink, the mould-jacket is important for the fuse-characteristics and it also provides full electrical insulation.
All specified parameter are valid through the resistance-range from 0R1 to 1K0.

More information about BWF Series