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7 tips on Fuse direction, Fuse polarity

Time:2021-07-27   Author:Bussmann fuse product manager   Browse:

On Bussmann Power website, some engineers are asking:

What's the  fuse direction/orentitation? Polarities on Fuse Holder?

Do fuses have a positive end and a negative end, or can they be put in either way?


Fuse direction Bussmann fuse.jpg


1, Some fuses are with different size, different shape on both sides. 


Such as FNQ-R, 170M3816 etc.


170M5145 series high speed fuseFRN-R  series time delay fuse600V cable limiterBottle fuse Bussmann 25D27Q
170M5145 high speed fuse Bussmann.pngFRN-R Bussmann fuse.pngK 600V cable limiter.jpgbottle fuse Bussmann E27.png



2, Some fuses are with microswitch, indicators. 


Fuse is not with positive or negative side, but some fuse in fusing will pop up a red tip, to start the switch cabinet on fuse cannot work, should be paid attention to when the fuses will melt,  one end of the tip in the indicator position, although put wrong position does not affect its function, but may not be directly recognized when melting because the indicator side is put inside.

170M3973
170M3816ANL, ANN fuse

170M3973 fast blown fuse.png170M3816 fast acting fuse.pngANL, ANN very fast acting fuse.png


3, Is  semiconductor fuse  with direction?


There is no polarity on semiconductor fuse, so there is no positive or negative side in fuse. The difference between semiconductor fuse with the time delay fuse is the semiconductor fuse is made of pure silver, which has the characteristics of short  circuit  and fast melting speed, so it is also called  fast acting fuse


4, Why there is DC fuse neeed in both positive and negative side in DC control power supply?


It is mainly a safety problem. If the AC power is directly grounded in the  transformer  distribution cabinet, the leakage protector will can not be installed. So there will be big safety risks. In fact, the AC power is grounded in the distribution cabinet security device source.

Also because the DC current is obtained by AC rectification,  There is voltage to ground on both the positive side and negative side.   To add the DC fuse can avoid the  short circuit leakage to the ground damage to circuit.


5, Should I design the  DC fuse on both positive and negative side on both side of the single-phase bridge rectifier circuit?


Why do DC  circuits  have fuses both positive and negative terminals?


Does it matter if you put switch/fuse in a DC Circuit on positive terminal or negative terminal?


If the circuit is in positive pole to ground, you can use  high speed fuse  on negative side; If it's negative pole to ground, you can use a  fast acting fuse  on positive side.

It is absolutely right to add fuses to both the positive and negative poles, It's better to add both, because you don't know where the short circuit is happening. If the cost is limited,  it is also possible to add only one fuse to the positive pole under special circumstances.



6, Can I use a fuse in a negative wire?


It depends on the circuit. Suggest to add fuse on both positive and negative side.


7, Is there fuse direction on fuse?


No. Fuse is a conductor in normal circuit. So it's without any direction or polarity and orentation.

The fuse will cut off the current path due to the high temperature melting point of the fuse, regardless of the current direction.



More questions, you can  contact us  for detail.


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


TAG:   Fuse direction Fuse polarity