Is Voltage Rating Important in Fuses ?

Yes! The voltage rating of a fuse is the maximum DC or RMS voltage the fuse will be able to safely interrupt during a fault condition. I suspect the vendor knows both this fact and the actual voltage used in this VFD to select this alternative fuse.

This happens if you get it wrong

Is the "vendor" just a fuse vendor or the machine vendor?

I'd get the right (600VDC) fuse.

Yes voltage rating is very important.

Having said that, the 300 volt unit may be an acceptable fuse. Vendors will often get a fuse of a higher voltage rating when the correct lower voltage one is not available to them.

Verify with the vendor that the 300 volt unit is acceptable.

Verify with the vendor only as long as the vendor in question is the vendor of the machine or the vfd.

If the "vendor" is just a fuse vendor... return the 300 volt ones.

Good point, thanks.

This is a curve from a SIBA catalog showing the effect of voltage, less than rated maximum, on I²t let-through of fuse.

Sorry about poor copy quality. The point is that the let-through at half rated volts is about 0.6 of that at rated volts.

The question for you is... did the designer choose a higher voltage fuse of same size & current to reduce the energy and damage resulting??

You must query the makers of the two fuse types to get a comparison.

67model

I had experienced the same as this, it did not last 1 min.

Silly me, but do we know who the first fuse failed?

If not, I'd buy a six-pack of fuses.

These probably a silly question(s).

1. Why did the fuse blow?

2. A 150 Amp/600VDC slow-blow fuse is awfully big. Is this an OEM Circuit Interrupter?

3. Have you corrected the problem with the VFD before considering a NEW fuse?

If the OEM supplied a 300VDC fuse. the 600VDC fuse must have been the copper-penny behind the fuse.

As long as the voltage of your service is less than the rating on the fuse, you are ok.

You are absolutely correct.

I must have been half asleep..it blew right by me.

I was too absorbed in the forest to see the trees.

There are certain special fuses that have a small form factor with 600volt rating,but not at the high ampere stated by the OP.

You get A GA from me.

IMHO,should not have been marked OT.

230 (sqrt 2) ~~ 325.2 > 300.

The peak voltage instead of the RMS voltage is not a concern. However, a phase to phase short circuit in a three phase motor is a possibility this fuse might have to interrupt.

230*√(3)≈400

My point here is that we once again do not know enough information to answer if a 300 Volt fuse can be a proper substitution for a 600 Volt fuse. It all depends on the application that we do not know.

(Remember: 230 VDC was a proffer by JRaef. This is not a given condition by the OP.)

Definitely not off topic....BUT....the peak voltage sometimes does matter.

As you noted all the SWAGs so far have been those of the faceless learned council only.

More info pls OP.

Some really good answers here already. I personally would have looked for the 600 Volt version, assuming that the original type was 600 V, until I had 100% proved that a 300 V version was fully acceptable....

For the OP, just for interest, some really good High voltage fuses may have a "filling" of some sort to improve the "break" resistance and reduce the possibility of an arc forming.

I believe it used to be dry, clean sand years ago (it looked like sand) , that would melt and form an extra insulating silicon "barrier" preventing an arc.

Today, it may be something else, something better, something faster maybe.....but as I have not taken a fuse apart for probably almost 50 years.....I cannot say.

I know that I always picked the sand filled ones, over air/gas filled ones, provided of course, that I knew which was which (after taking some apart previously of course!!), that was easy!

I never realised till fairly recently, just how expensive good quality high current, high voltage fuses can be.

Furthermore, I have read somewhere (here on CR4 maybe?) just how often they are "faked" in the far east nowadays!!! Be warned!!

Reading manuals may help you get the facts. Here is a useful source to dig in(see DC bus voltages pp 2,3,4) : Rockwell Allen Bradley

I bet you're popular with your insurance company, Mildred!

Do you really expect an answer when you haven't told me the voltage on your VFD bus?

Yes Mr.Dhanesh.koshti,

The Voltage Rating for Fuse is Very Important and Specs for AC Fuse, DC Fuse as well as Fuse for Neutral is clearly defined as Specifications.

Selection of Fuse is to be carefully decided. Pl. open the following links and you will learn that Voltage Rating is very Important while selecting a Fuse.

https://www.google.co.in/?gfe_rd=cr&ei=l_9bVsLPIuyK8QelgqSYAg&gws_rd=ssl#q=fuse+voltage+rating+importance

http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Voltage_Rating.pdf

https://www.quora.com/Why-do-fuses-have-voltage-rating

· A resettable fuse rating is 2A 250V. What does this mean?

· Why are fuses rated by amperage rather than power?

· While designing an electronic device, when would you not use a resettable fuse instead of a conventional (non-resettable) fuse?

· What are the specifications of a neutral fuse?

· Which fuse will blow first?

DHAYANANDHAN.S

Please state in which electrical code(s) a fuse may be permitted in a neutral conductor?

The NEC requires that ALL conductors,including the neutral, be disconnected by the

same ganged circuit breaker on gasoline pumps.

(Class1 hazardous location.)

No mention of fuses,however.

Remember,however that not all neutrals are grounded.

If the NEC does not state that fuses are acceptable for a certain location or a certain category of equipment, than you can assume that fuses are NOT ALLOWED.

But since this is replacing an existing fuse, the new fuse should match the specs of the old one exactly. Same max voltage, same max current.

Surely a fuse with a higher voltage rating, but otherwise exactly the same, could be used?

For instance Physical characteristics of size, current rating, HRC/speed of rupturing?

Please explain for me why not, thanks in advance.

Yes, you can use a fuse with a higher voltage rating. The rating, as stated by another poster, is simply the max voltage that can be confidently stopped by the fuse, instead of 'arcing' through the air gap of the blown filament.

The problem would lie in physically installing the fuse, as higher voltage fuses tend to be physically larger (to provide a larger air gap once the fuse blows) and the larger fuse may not fit in the existing fuse holder.

The problem would lie in physically installing the fuse, as higher voltage fuses tend to be physically larger (to provide a larger air gap once the fuse blows) and the larger fuse may not fit in the existing fuse holder.
I thought I covered that in my post - only difference I was inquiring about, because you wrote that it had to be the exact same voltage, being the voltage!
But its now answered I believe:-
"If the only difference is a higher voltage, that is acceptable!"

I have also heard of it being done, tantamount to suicide!!!

Which hose will squirt water further,one with 300 psi or one with 600 psi?

The same applies to fuses.

It is harder to quench the spark from 600 volts than from 300 volts,so the internal

design of the fuse takes this into consideration.

If you actually have 600 volts on the fuse,it is not proper to replace it with a 300 volt

rated fuse.

But,as always,verify with the vendor if you are not sure.

Please provide manufacturer name and part number of each fuse for me to

compare,also,the VFD manufacturer name and model number.

More info will get better results.

There is one aspect of this question that is missing. That is...

Voltage ratings are important in EVERYTHING we do and not just with fuses. Equipment is designed to operate as it should when exposed to electrical energy levels that match the design criteria the items were built to.

There is little more important, other than perhaps current ratings, then matching equipment voltage ratings to the nature of the system voltage.

Fuses are a well developed science of their own.....With them, you don't want an arc developing after the fuse is blown, so its basically the applied voltage which specifies the minimum distance between the two electrodes (as a word to use!) left.

The greater the distance, the less likely that an arc will form.

In the Wiki article I found this impressive sentence:-

Voltage rating of the fuse must be equal to, or greater than, what would become the open circuit voltage.

To make the effective arc distance greater, some fuses are filled with other things like dry sand (at least it looks like sand!), that increases the "way" between the grains and works as a greater distance for the arc to travel.

This also helps to make certain special fuses more "HRC", High Rupture Capacity, mainly assisted by many thin fusible wires and the metal(s) from which they are made, instead of just one! Which allows a fuse to handle a high starting current, like that for say a 3 phase induction motor, without blowing, but if say a field is open, the high current will continue to be pulled and will after a specified time, blow fuse(s).

Sadly, sometimes only one of the three blows! Which for amateur electricians, is a dangerous mystery, which is why you REALLY need to know what you are doing and why!!!

Plus if an arc still develops, the sand then melts and forms a further helpful insulating barrier.

As I mentioned earlier in this blog, in modern fuses they may have something better, though as no one here commented on that point then, that may have NOT changed as much as I expected.....which is surprising really!

There is a nice dissertation here on fuses:-

Fuses

I think that you mean an arc does not escape the volume of the fuse and not that an arc does not occur. An arc occurs every time a circuit is mechanically interrupted, even with a properly working and rated switch. This is why the contacts of a switch become pitted.

I actually meant that any arc formed is rapidly "put out", primarily for the reason that the "distance" between electrodes is made to be too great to allow the arc to sustain.

Possibly a filling "increasing" this distance.

With switches and breakers, there is sometimes a "quenching" circuit, using possibly sudden greater distance between poles or even series magnetic coils in a "hood", that magnetically "blows out" the arc using basic motor principles as long as current is flowing. e.g. arc sustained.

Right Hand Rule.

See here:-

Right-hand-rule