Fuse Ratings FAQs
1. Can the fuse voltage exceed the application voltage?
2. How should I select the proper fuse amperage when I know the circuit amperage?
3. What is the difference between interrupting rating and the fuse's ampere rating?
4. Why is the interrupting rating important?
Can the fuse voltage exceed the application voltage?
Yes - Fuses are designed for use in circuits at any voltage as long as they don't exceed the fuse's maximum voltage rating. (Exception - medium-voltage fuses from 2,400 to 38,000 volts may only be used at the voltages designated on the fuse's label) The voltage rating of a fuse is a safety rating that should never be exceeded.
How should I select the proper fuse amperage when I know the circuit amperage?
Always follow NEC guidelines for applying low-voltage fuses. Generally, the MINIMUM fuse size should be based on 125% of the circuits full load current. Time-delay fuses should be used for inductive loads and fast-acting fuses used to protect non-inductive loads.
What is the difference between interrupting rating and the fuse's ampere rating?
The interrupting rating is the maximum amount of energy the device can safely withstand. The fuse's ampere rating is the amount of current that the fuse will allow through before beginning to operate. Both ratings are determined through testing.
Why is the interrupting rating important?
The interrupting rating is important because it is a safety rating. If a device with a low interrupting rating is used in circuit that has a higher available fault current (the amount of energy that is potentially available if a fault were to occur), the device could potentially fail (rupture or explode) as it attempts to clear the fault, causing a safety hazard.
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