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SF240 Datasheet(PDF) 7 Page - NEC
SF240 Datasheet(HTML) 7 Page - NEC
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The body temperature of the thermal cutoff becomes higher as current passes through and might rise higher
than the ambient operating temperature (see test data). The temperature may rise even higher depending on
the mounting method and other conditions. Therefore, after mounting the thermal cutoff under the same
conditions you would use for the actual application, work the final product and measure the body temperature
of the thermal cutoff.
Use the thermal cutoff with a voltage and current level lower than the rated level.
If the thermal cutoff is used with a voltage or current level higher than the rated level, contacts may melt
causing the fuse to malfunction.
Do not use the thermal cutoff in water, organic solvents or other liquids, or environments containing sulfurous
acid gas, nitrous acid gas, or high humidity. Doing so will cause deterioration of the sealing resin, the thermal
cutoff may operate at lower than operating temperature, or any other malfunctions may occur. Also, the
thermal cutoff may not operate even if its operating temperature is exceeded.
Lead wire process
When bending the lead wire, in order to protect the resin seal from excessive pressure, secure the lead wire
cIose to the case and bend the part beyond the secured section.
3 mmor more
SEFUSE can be mounted by soldering, caulking, or welding.
If soldering, note that the thermal cutoff may not function because of excessive solder temperature.
To prevent such malfunctions, you can hold the lead near the case using a tool and solder for short intervals
at a time, allowing the heat to escape.
Another effective method is to use a lower solder temperature and to solder at a location that is distant from
If caulking or welding, be careful to keep the resistance value of the connecting section low.
If the connecting section has a high resistance value, the passing current may generate an abnormally high
temperature that will cause the thermal cutoff to operate (break the circuit).
Deformation of the case may change the location of the moving electrode during operation and may cause the
thermal cutoff to operate only at temperatures lower than the normal operating temperature range. The ther-
mal cutoff also may not operate even if the thermal cutoff's operating temperature is exceeded.
0.8 steel wire
The lead wire should be bent at a distance 3 mm or more from the body of the fuse, and should not be twisted.
The tensile strength applied to the lead wire should be 5 kg or less.
The strength applied to the body of the thermal cutoff should be 10 kg or less.
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