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Do current limits also apply on lower voltage?

For example:

I have a wire/fuse that is rated for 2A. I usually runs it at 10VDC. Then, I use 5VDC with 3A load. Will the fuse blow?

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2 Answers 2

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Yes, the fuse only reacts to current.

The fuse does not "see" what voltage is applied, the fuse reacts only to the current flow. If you connect a lower voltage to your circuit, then the load impedance can also be lower before the maximum current is reached, but the value of the maximum current stays constant.

Fuses do have voltage ratings, but they mean something different: The voltage rating of a fuse tells you, up to which voltage the fuse guarantees to work. If the fuse has a rating of 500 V, then it might fail for an applied voltage of 750 V by arcing over.

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  • \$\begingroup\$ Note that fuses are not terribly precise, a 3A load on a 2A fuse will probably cause it to fail eventually, but that might be in an hour. Fuses are generally protection for wiring, do not try to use them to protect semiconductors, it does not (generally, there are some very expensive ultra fast fuses) work. \$\endgroup\$
    – Dan Mills
    Mar 30, 2021 at 10:23
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If too much current is flowing, the fuse will typically melt. The current rating for fuse is found by actual current/0.75. The voltage rating is important as well which means the safe operation of fuse at maximum voltage in situation of overcurrent.

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