N vs E Fuse 1

[Mbrooke]

Where would a type N fuse be used? Its seems like most HPA fuses are type N which is confusing the daylights out of me.

 

[cuky2000]

Fuse selection is influence by accuracy, pricing, availability, standardization, and even preference.

Below is a quick comparison of type N & E fuses.

 

[Mbrooke]

Thanks- but what benefit does a 115% pickup provide over 200-220%? I can see a type N link blowing all the time.

 

[RRaghunath]

Mbrooke, Could it be the fuse that is blowing frequently is with PX type fuse element.
The PX type element is fast acting (within type 'N' range) and may not remain stable during transformer energisation.
I got this from fuse literature.

 

[Mbrooke]

There is SS PF which is slow- but still starts at 115%.


One benefit that I can see to a type N fuse is that it can easily be set to blow right before the transformer's damage curve in regards to sustained overload- but S&C seems to frown on that.

 

[RRaghunath]

Starting at 115% is OK unless the transformer is continuously works beyond its rating, isn't it!
The concern I was mentioning is about the inrush currents for which the fuse has to be stable for 12 times the rated current for 0.1s.
The type PX is rated for 7 times (0.1s) only.

 

[Mbrooke]

What about EPR feeders? Why does S&C support (push) E type fuses for these applications?

 

[RRaghunath]

Mbrooke, I am sorry if you have misunderstood me to be S&C staff! I am not.
I don't understand 'EPR' feeder!
For me, EPR is one type of insulation used in power cable construction - Ethylene Propylene Rubber

 

[Mbrooke]

Yup- protecting underground cables. I should have used a different term, especially when I myself am terrible at acronyms, abbreviations and 3 letter words.

S&C doesn't offer any N fuses, or at least not outside of fuse links for overhead cutouts. All their application literature references E and K fuses, along with their various advantages. It seems like S&C does not think N fuses are good fit in utility and institutional power systems.