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Short circuit current LiFePO4 Battery

But a 10 amp cell won't have the same amount of amps flowing compared to a 1000 amp under a fault condition (ie direct short)- I'm trying to calculate fuse/breaker break load capacity (the load at which the fuse/breaker can sustain before being destroyed - not to be confused with trip current).
You are correct. As is AntronX. A higher-capacity cell will have a lower internal DC resistance.
 
OK, it's sinking in now. So a 56v LIFEPO4 pack 16s 280amp (with a resistance of .21 mΩ would be 56/0.0021 - approx 26kA. What about a 4p16s pack (1120amp x 56 volt)?
Thanks
 
No, 0.21 mOhm is per cell. Entire 16s pack would be 0.21 * 16 = 3.36 mOhm (not including busbars).
 
OK, it's sinking in now. So a 56v LIFEPO4 pack 16s 280amp (with a resistance of .21 mΩ would be 56/0.0021 - approx 26kA. What about a 4p16s pack (1120amp x 56 volt)?
Thanks
Well, everything else being equal (not that it is), but 1/4 the resistance. But see @AntronX above
 
No, i was thinking of using that fuse for the group of batteries. I will be having two more groups (each with a NH00 125A fuse), so in totalt nine 15kWh batteries.
The caracteristics is shown here:

View attachment 237650
View attachment 237653
View attachment 237652

That charts you show here are probably for AC. You cannot use them for DC.
The correct type of NH fuse ist type gR.
Some manufacturers of gG fuses also specify how to derate them for DC. However that is manufacturer specific, see their data sheet.
 
At the time a fuse interrupts a current, an arc forms.
Electrical arcs require a certain minimum current to continue. Everything else equal, with AC the arc stops at the AC current zero crossing and a new one (may) start once the minimum voltage/current condition is reached again. With DC the arc is continuous. As a result, DC is much harder to switch, disconnect or fuse. Thus you require specialised fuses, switches, connectors, breakers, etc.
As an example just look into the datasheets of fuses or relais, and compare AC and DC ratings.
 
At the time a fuse interrupts a current, an arc forms.
Electrical arcs require a certain minimum current to continue. Everything else equal, with AC the arc stops at the AC current zero crossing and a new one (may) start once the minimum voltage/current condition is reached again. With DC the arc is continuous. As a result, DC is much harder to switch, disconnect or fuse. Thus you require specialised fuses, switches, connectors, breakers, etc.
As an example just look into the datasheets of fuses or relais, and compare AC and DC ratings.
So how do you mean the physical structure of a NH00 fuse differs if its gG or gR?
I would like my fuse to handle some overload, like peaks of normal current, but cut the arc fast on a short-circuit issue.
 
So how do you mean the physical structure of a NH00 fuse differs if its gG or gR?
I would like my fuse to handle some overload, like peaks of normal current, but cut the arc fast on a short-circuit issue.
The gR is designed and tested for the special needs of DC.
The gG is designed and tested for AC.
Typically, if you compare the same fuse, the gR version has lower ratings for open circuit voltage and short circuit current. How much lower is model specific. E.g. a random fuse from Siemens 3NA3836 160A, is good for AC 500V/120kA, But for DC it is only good for 250V/25kA.
 
The gR is designed and tested for the special needs of DC.
The gG is designed and tested for AC.
Typically, if you compare the same fuse, the gR version has lower ratings for open circuit voltage and short circuit current. How much lower is model specific. E.g. a random fuse from Siemens 3NA3836 160A, is good for AC 500V/120kA, But for DC it is only good for 250V/25kA.
Found this: https://hal.science/hal-04192068/document

"aR and gR fuses, often referred as “high-speed”,“ultra-fast” or “semiconductor” fuses, are dedicated to power electronics converter and DC applications with a minimized thermal stress, peak current and arc voltage [10]-[12]. On the other hand, existing AC distribution grids use gG fuses whose requirements are described in [13]. Both technologies may be suitable for LVDC distribution grid."
 
So how do you mean the physical structure of a NH00 fuse differs if its gG or gR?
I would like my fuse to handle some overload, like peaks of normal current, but cut the arc fast on a short-circuit issue.


 
Found this: https://hal.science/hal-04192068/document

"aR and gR fuses, often referred as “high-speed”,“ultra-fast” or “semiconductor” fuses, are dedicated to power electronics converter and DC applications with a minimized thermal stress, peak current and arc voltage [10]-[12]. On the other hand, existing AC distribution grids use gG fuses whose requirements are described in [13]. Both technologies may be suitable for LVDC distribution grid."
gR fuses are called "semiconductor" fuses unofficially by older utility grid people. Back then, DC was only used with semiconductors (inverters, VFDs).
Actually, the "R" of gR is the abbreviation for "Rectified" current.
"a" type fuses are faster than "g" type, because "a" is designed for short circuit protection only. "g" is also for overload protection.
You can use a gG for DC, if the manufacturer specified and tested it for DC. But you cannot use the AC ratings for a DC design.
 

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