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Medium voltage fuse Q&A

Time:2022-05-05   Author:ABPower PM   Browse:

Medium Voltage Fuse Types

Fuse application- Base on fuse application ( Transformer, Motor, Switchgear etc), there is: 

Motor fuse, Fuse catalog No. example:  3.6WKFHO315, 7.2WFNHO63, K81ERX315,  3.6WDLSJ100, 2.75VFRHA4R,5.5VFNHA4R;

Transformer protection fuse, Fuse catalog No. example:  1.1NBUN*3.15, 3.6ABCN*6.3, 5.5AMWNA4E;

PT fuse (Potential transformer fuse), Fuse catalog No. example: 7.2AMWNA3E,12ABCN*3.15, 15.5ABFN*3.15, 17.5ABGN*3.15;

Switchgear fuse (Air fuse), Fuse catalog No. example: 3.6CAV2,  5.5CAVH2E,  7.2CAV10, 24CAV3; 

Oil fuse, Fuse catalog No. example:  3.6OEFMA100, 7.2OHGMA160,  12OHGMA20,  15.5OEFMA31.5, 24OEGMA50

E-rated fuse, for feeder circuit, switchgear and transformer protection,  Fuse catalog No. example:  8CLE-_E, 15HLE-_E, 15LHLE-_E.

high voltage fuse 12KV 15.5KV 24KV.png

For the medium voltage fuse size and type detail, you can find it here: 

What are Medium voltage fuse size and types?

Fuse range

In Bussmann medium voltage fuse, there is 3 fuse ranges applied:

"F' Range-- It means full range fuse links; Fuse catalog number example: 

"T" Range-- It's backup fuse links, with fuse striker;  Such as: 

"A" Range-- It's including high current rating back-up fuse link. E.g: 

Fuse range diagram as below:

MV fuse range.png

Also , here is a brief indroduction on Bussmann medium voltage fuse catalog Number meaning.

Bussmann medium voltage fuse catalog number.png

Medium voltage fuse classes

Fuse classes are not available for Medium Voltage fuse, Why?

Medium voltage fuses are applied quite differently than fuses rated 2000 VAC/DC and less. The biggest difference is that medium voltage fuses are not intended to provide overload protection to devices. They should only be applied in situations where it will not be required to open small overcurrents. Medium voltage fuses offer a much wider range of system voltages ( 1 kV to 72.5 kV base on IEC standard), thereby resulting in a correspondingly large number of fuse voltage ratings.

Medium Voltage Fuse Speed

The speed for the fuse? Is it Fast, Slow, Very Fast, Very slow or any other? 

For medium voltage fuse this is not applied.  High voltage devices acting speed is much longer than low voltage devices. Depends on arcing time.

MV Fuse are choice of distribution circuits due to their speed of operation and current limiting ability in the event of a short-circuit fault. The diagram below shows the operation of a fuse link interrupting a short-circuit fault, achieving a current zero well within thefirst half-cycle of a fault. Energy let-through into the site of a fault maybe typically only 1/500th of that of any other type of switching device.

MV fuse speed.png

Medium Voltage Fuse Curve

For medium voltage fuse, there are normally : Time - current characteristics curve,  cut-off current characteristics curve, Peak Let-through curve.

Q1: As we can see there having dotted portion at the upper part of the curve. Whether the curve operates in this region or not? 

A:No, the dotted portion side no action.


Q2: Why are some current level curve are missing in fuse curve?

A:  All fuse manufacturers  will not send all current level fuses to test. Only some current level, The other current level curve are simulation.

Q3:  Whether the A-B line shown on the below curve representing Asymmetrical RMS Amps or Symmetrical RMS Amps line. (For 3.6kV, 7.2kV, 10kV)?

A: The left side of lines A-B is an area with no finite flow capacity.


There are more medium voltage fuse questions, will update concinuously.

New industry Technology regarding to Bussmann fuse, ABB breakers, Amphenol connectors, HPS transformers, etc.