It is established by Littelfuse as a value of current which the fuse, fuseholder, fuse clip or other fuse accessory can carry, based on a controlled set of test conditions.

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The maximum RMS AC voltage and/or the maximum DC voltage at which the fuse is designed to operate. For example, fuses rated at 600 volts and below may be applied at any voltage less than their rating. There is no rule for applying AC fuses in DC circuits such as applying the fuse at half its AC voltage rating. Fuses used on DC circuits must have DC ratings.

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Refers to how rapidly the fuse responds to various current overloads. Fuse characteristics can be classified into three general categories: very fast-acting, fast-acting or Slo-Blo® (time delay)fuse. The distinguishing feature of Slo-Blo fuses is that these fuses have additional thermal inertia (surge withstand) designed to tolerate normal initial or start-up overload pulse.

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RMS Surge (Non-repetitive) On-state Fusing Current- Measure of let-through energy in terms of current and time for fusing purposes.

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Cold resistance is the resistance obtained using a measuring current of no more than 10% of the fuse's nominal rated current. The factory should be consulted if this parameter is critical to the design in question.

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Color or Alpha-Numeric code used to define the amp rating of the device for ease-of-maintenance and quality checks.

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