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Matt
New Member
USA
2 Posts |
 Posted - 01/17/2009 : 22:24:06
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Hi Guys, I have a interesting one.
I have always been taught that fuses blow when the amps go abouve what they are rated for. If this is the case, then why can fuses of the same amp rating have different voltage raings? Ie: FRS-R-30 600v and FRN-R-30 250v? I know that these examples have different physical sizes, but I am curious about the voltage aspect. Can a fuse blow if I installed a 250v fuse in a 480v circuit and not pull more than the fuse can handle? Nobody can give me a good answer.....
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robotmagic
Forum Aficionado
USA
536 Posts |
Posted - 01/17/2009 : 23:27:54
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"Can a fuse blow if I installed a 250v fuse in a 480v circuit and not pull more than the fuse can handle? Nobody can give me a good answer....."
The circuit voltage has nothing to do with the fuse until it blows, then the peak voltage will be across the open fuse and the fuse must safely withstand the voltage.
A high voltage fuse may be spring loaded or filled with ceramic powder to help interrupt the arc, while a low voltage fuse may just be a thin wire in a tube.
Fuses come in many shapes and sizes,
A fuse is rated by rated current, current interrupting capability, time, and voltage.
A 10 AMP fast acting “rectifier” fuse will blow 100 times faster than a 10 AMP dual element time delay fuse.
A fuse protecting sensitive electronics has to be fast, while a fuse protecting a motor has to be slow to allow startup current.
A fuse must be able to interrupt the peak voltage of the system it is installed in and the peak current it may encounter.
There really is a lot to fuses, here is some info for you to dig into.
http://www.bussmann.com/library/docs/spd05/spd05-s15-pp202-216.pdf |
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JRaef
Active Member
USA
88 Posts |
Posted - 01/18/2009 : 11:40:53
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robotmagic is dead on. Just to add a note of clarity though, you can technically use a 600V rated fuse on 250V, but not the other way around. Practically however, it may not work because fuse clips are designed to reject* fuses of the wrong voltage rating. Amps are amps, but as robotmagic said, fuses are often expected to do a lot more than just protect for high amperage.
*(not allow them to be plugged in) |
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BrianJohn
Avid Member
271 Posts |
Posted - 01/19/2009 : 13:26:43
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| Fuses (most/many) do not blow immedatly when they exceed their current rating this is a time current issue and is dependent on fuse type (as noted above). Bussman has some excellent literature regarding fuses, fuse types, AIC rating, time/current curves and fuse applications.. |
Brian John
Leesburg, VA |
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John A. Peters
Forum Magnate
USA
1852 Posts |
Posted - 01/22/2009 : 20:12:08
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Wow, good info guys!
They also blow out under normal curent loads, due to old age. (Victorian houses ya know) |
Same Day Service 415-239-5393 SF Electrician SF John A. Peters, San Francisco CA www.BrooklineElectric.com/ |
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balakrishnan
New Member
India
1 Posts |
Posted - 04/03/2009 : 01:13:59
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Fuses are always expressed with amps rating but the working is based on the power rating that is voltage and current,power=I2R or VI and when the heat developed in fuse material {P=I2RT} it blows down .hence it is advisable to use proper voltage rating fuse.
quote:
Originally posted by Matt
Hi Guys, I have a interesting one.
I have always been taught that fuses blow when the amps go abouve what they are rated for. If this is the case, then why can fuses of the same amp rating have different voltage raings? Ie: FRS-R-30 600v and FRN-R-30 250v? I know that these examples have different physical sizes, but I am curious about the voltage aspect. Can a fuse blow if I installed a 250v fuse in a 480v circuit and not pull more than the fuse can handle? Nobody can give me a good answer.....
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JimmyDee
Admin
USA
4177 Posts |
Posted - 04/03/2009 : 07:56:43
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quote:
Can a fuse blow if I installed a 250v fuse in a 480v circuit and not pull more than the fuse can handle? Nobody can give me a good answer.....
The voltage rating on the fuse has nothing to do with the fuse blowing or opening up. That is amperage dependent. What you asked if I understand you correctly, your question is about putting a fuse in that is rated for a lower voltage than the circuit is designed for. This could be very dangerous. A lower voltage fuse could blow up like a bomb with a higher than rated voltage applied.
The guts of a fuse are designed to open up while quenching the arc in side of the fuse with nothing else exciting going on in the fuse. A higher than rated voltage on that fuse could allow the arc that is developed in the fuse, when it opens up, to go ballistic and cause a great deal of damage outside the fuse. This could be as minimal as a burnt fuse all the way to blowing the cover off the panel or box the fuse is in. NEVER use a fuse that is rated for a voltage less than the applied voltage. Could cause damage to equipment or injury.
Jim |
A moderator on this site is a member, just like you're a member. My opinions are no more valid than your opinions, so feel free to disagree with me on any subject. A Spell Checker for Your Forum Posts, By IESpell; CLICK HERE for a Free Copy. CLICK HERE for Mozilla Foxfire 3.5. Spell check built in. They are free and they work! |
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cchongj
New Member
USA
1 Posts |
Posted - 02/07/2010 : 22:45:19
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quote:
Originally posted by Matt
Hi Guys, I have a interesting one.
I have always been taught that fuses blow when the amps go abouve what they are rated for. If this is the case, then why can fuses of the same amp rating have different voltage raings? Ie: FRS-R-30 600v and FRN-R-30 250v? I know that these examples have different physical sizes, but I am curious about the voltage aspect. Can a fuse blow if I installed a 250v fuse in a 480v circuit and not pull more than the fuse can handle? Nobody can give me a good answer.....
I am confused by your question. Fuse is measure in Amperes. |
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stm4839
Avid Member
USA
111 Posts |
Posted - 02/08/2010 : 19:29:44
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A few things some aren't aware of:
Be careful with fuse substitution, double check the interrupting capacity of the fuse. A fuse with a lower AIC than the available short circuit current can also go off like a bomb when it tries to clear a fault, and may be the same size/shape as the correct fuse.
Most standard size cartridge fuses have a much lower DC voltage rating than AC rating. Its fairly common for people unfamilliar with DC circuits to use the wrong fuse (at least around here). For example a 600 VAC RK5 dual element fuse is usually only rated for 250 VDC and that rating is usually burried in the fine print on a spec sheet. Again they can self destruct trying to clear a fault if incorrectly applied.
On the plus side, the proper fuse has a much higher interrupting rating and is substantially faster than a circuit breaker. So much so that some larger breakers have internal fuses in addition to the usual breaker trip mechanism to increase the interrupting rating of the entire assembly.
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The answer to the ultimate question of life, the universe, and everything is... 42 |
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srai044
New Member
India
1 Posts |
Posted - 02/10/2010 : 05:54:43
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| relay testing procedure |
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electromagician
Member
18 Posts |
Posted - 02/13/2010 : 12:53:05
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| You also have to keep in mind the arc fault rating of the circuit if you change the model of fuse. They type of fuse often will change the rating. This will change the level of PPE required to work in live panels. We are currently converting to low peak fuses inorder to lower the PPE level. |
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bytemylobster
Avid Member
Canada
409 Posts |
Posted - 02/16/2010 : 22:25:42
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Yes, absolutely, the fuse's voltage rating is how many volts the components can handle.
Better to go "higher".
I have seen a fuse that only failed as the load approached 60% of its rating.
Below that rating, the unit worked. Go figure. It was a DC to AC Inverter in Communications.
It is still a puzzle to me.
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lemau
Member
11 Posts |
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Fuse Ratings
