The voltage rating for the fuse is not a concern in this application, just the amperage rating.
The voltage rating is related to internal component arrangement proximity to avoid arcing. (creepage and clearances)
You would not use a 20v rated fuse in a 120v circuit. You can use a 120v rated circuit protection device in a 12v circuit.
Cheers,
But... using a 120vAC 30amp circuit breaker in a 12v application isn't going to work.
Yes, it will work fine. See below.
V*A=W (VOLTS times AMPS=WATTS
120v*30A=3600watts
12v*30A=360watts
Sorry, your premise is flawed.
The fuse does not consume all that power, only a very tiny portion to warm the element. So, your proposed power calculations are irrelevant and inappropriate.
P= I
2R. You don't even need a voltage to solve that equation. (While a voltage potential difference is required to allow current flow through the fuse, it is not what is critical to force it to melt.) It has a fixed resistance and the current flow through it generates heat above ambient. It's inline resistance is very small compared to it's current carrying ability. It consumes very very little power during it's use. What you should use for calculation is how much voltage is dropped across the fuse device itself (derived from resistance), if you still refuse to use the simpler P= I
2R equation.
Watts are Watts no matter what voltage you use.
Agreed.
Conversely, to run a 360 watt 12vdc circuit, you would need a 120v 3A source, as in a transformer. Now you could use a 120v 3A breaker to protect that transformer...
There is a difference on the load in Watts. You would never use a 120v 30A breaker in a 12v DC application. Not practical, either, as the breaker is 'huge' compared to the tiny little 30A breaker disguised as a fuse. So, if you are suggesting he try this, I don't think that's a good idea. He is trying to learn proper ways of working on DC circuitry, and telling him he could substitute AC components is really the wrong way to approach that.
Please follow the links on eBay, and order the appropriate parts. If you want to wire a 35WATT 12vdc bulb across the existing main fuse terminals, which have a spade connector between them now, get a 1156 socket from the AUTO parts store, and an equivalent bulb, and wire the two leads from the socket, under the two screws on that fuse connector, FOR TESTING PURPOSES ONLY. For operation, get that GL1100 Goldwing solenoid/harness connector/fuse holder in the link. And the 30A breaker in the other eBay link. Or a handful of conventional blade fuses (A BIG handful)
That is what should be recommended....
Charlie
I hope you'll retract that recommendation, as it is based on false and misleading assumptions.
FYI: I had to learn this stuff in my 30 years of electronic design, including power supply manufacture. They are fused as required by safety codes; UL, CSA, VDE, NEC, etc. Every country seems to have their own version to adhere to if you wish to distribute product in that country.
Cheers,
>>>Read this excerpt from the Littlefuse site:http://www.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_fuseology_selection_guide.pdf.pdf See page 4.
"As mentioned previously (See RERATING section), fuses
are sensitive to changes in current, not voltage, maintaining
their “status quo” at any voltage up to the maximum rating
of the fuse. It is not until the fuse element melts and
arcing occurs that the circuit voltage and available power
become an issue. The safe interruption of the circuit, as it
relates to circuit voltage and available power, is discussed
in the section on INTERRUPTING RATING.
To summarize, a fuse may be used at any voltage that is
less than its voltage rating without detriment to its fusing
characteristics. Please contact the factory for applications
at voltages greater than the voltage rating"