What is Protistor and what it does?

[m.art.y]

Hi,

This thing was in line with HV bus in one of the OEM batteries. It says Protistor BS000GB69V125. Does anybody know what it is and what it does?

[crasbe]

Looks like those are fancy DC fuses: https://ep-us.mersen.com/products/group ... round-body

[m.art.y]

Does this mean when it blows it blows? Would this help me in a crash situation as I have not got pyro fuses? 125A seems a bit low worried it might blow unintended although I only have 30ish kw( 50 kw peak) motor.

[muehlpower]

data sheet on this page.

https://www.kempstoncontrols.co.uk/P330 ... sku/200798?

[m.art.y]

data sheet on this page.

https://www.kempstoncontrols.co.uk/P330 ... sku/200798?

Yes but I'm struggling to understand the numbers in the data sheet.. was hoping somebody could explain.

[asavage]

Kinda related:



It's tricky to interrupt large DC currents, to effectively and reliably quench the plasma arc. Various magnetic and air movement techniques are used.

[m.art.y]

So my motor is only rated for ~50 kw peak and 30 kw continuous power from what I could find but I have measured up to ~140A for a few moments under hard acceleration. Does this mean this protistor rated at 125A is too weak and would certainly blow under hard acceleration? I have put it inline the main HV cable from the battery but now thinking to take it out as if it is too weak and it blows under hard acceleration it could leave me stranded or damage the inverter?

[asavage]

I'm going to generalize.

Fuses protect wiring. Their job is to prevent wiring overheat -> fire.

Unless they're special purpose (eg "fast blow", and especially the somewhat misleadingly-named "semiconductor fuse" types, common on old Teslas and my car as well), almost all fuses -- and circuit breakers -- are designed to fail on a amps/duration curve, where for example they might not fail when run at 100% rated value; will fail at 110% rated value after nn seconds, or might fail at 130% rated value at 0.5n secs.

Those are merely example figures, but should illustrate that a circuit interrupting device that is triggered by current flow can operate very differently from another, similar device, and just because they're both labelled "fuses" doesn't imply they have similar characteristics; each has to be examined on its own merits.

Which is a long-winded way of saying that perhaps the 125A device you have is suitable for short duration 140A excursions. IDK, but I know I wouldn't be able to generalize, based on just an "125A" rating. It's more complicated than that. I've certainly had too much wine tonight to go look at a datasheet.

[m.art.y]

Which is a long-winded way of saying that perhaps the 125A device you have is suitable for short duration 140A excursions. IDK, but I know I wouldn't be able to generalize, based on just an "125A" rating. It's more complicated than that. I've certainly had too much wine tonight to go look at a datasheet.

Unfortunately rhe fuse I used is a protistor pictured above which in a datasheet is described as a ultra-fast acting. There is no curve given so I assume it would blow instanstly once over 125A?
https://www.kempstoncontrols.co.uk/P330 ... sku/200798

[asavage]

Unfortunately the fuse I used is a protistor pictured above which in a datasheet is described as a ultra-fast acting.

I don't find the word "acting" or "fast" in either the Mersen (Ferraz Shamut) datasheet nor that web page's description.

I do find the "semiconductor fuse" diode symbol on the fuse's labeling, though.

There is no curve given so I assume it would blow instantly once over 125A?

I, too, don't find a time/current graph, but they do furnish the raw I²T numbers for melting amps and total clearing amps (ref.):

Ferraz Shamut Mersen BS000GB69V125 datasheet fragment

Interpreting this is well outside my wheelhouse, and I'm certain someone will jump in shortly to bring context to those numbers; meanwhile, LittleFuse has more to say about I²T (ref.):

LittleFuse i²T explanation

[EV_Builder]

I2T is a way to describe absorbing capabilities. Like a bucket; when its full it trips. But the bucket has a hole so if the fuse gets time to rest the bucket will empty; is it being over used during T time it will trip.

That's what I2T means and does.

So basically it gives an idea what the above nominal accepted performance is. A "slow" fuse has a big bucket, a "fast" fuse a small one. Often the bucket is drawn in a graph where current and time are plotted.

[m.art.y]

So basically it gives an idea what the above nominal accepted performance is. A "slow" fuse has a big bucket, a "fast" fuse a small one. Often the bucket is drawn in a graph where current and time are plotted.

So how small is the bucket of this 125A fuse according to the datasheet below? If under hard acceleration my amps go to 140A for a couple of seconds would it blow instantly or is there still time to empty the bucket?

[m.art.y]

Not feeling easy about that protistor being sufficiently rated so I pulled it out. If I used 2 of those in parallel would I double the rating or is that a bad idea?

[EV_Builder]

The biggest issue might be absence of a DC rating. DC fuses aren't same as AC fuses. AC crosses 0 and that extinguishes the arc. DC needs other means for that.

[m.art.y]

The biggest issue might be absence of a DC rating. DC fuses aren't same as AC fuses. AC crosses 0 and that extinguishes the arc. DC needs other means for that.

Thanks for pointing that out. So that protistor is an AC fuse after all? It was used in one of the OEMs battery pack. So is there a chance it can handle more than 125A DC then if it's rated for 125A AC?

[EV_Builder]

Often the Voltage DC rating is less. The Arc needs tobe extinguished.
My observation is distance (bigger length fuse).

If it's used and you have exact type nr then it should have a rating. But then my question is what's the different in use ase (why have doubts then)?

[m.art.y]

Often the Voltage DC rating is less. The Arc needs tobe extinguished.
My observation is distance (bigger length fuse).

If it's used and you have exact type nr then it should have a rating. But then my question is what's the different in use ase (why have doubts then)?

I got worried by not understanding how these fast acting fuses work. I thought if the amperage goes slightly over it's rating (which is 125A) the fuse will blow immediately. But after searching a bit more on the web I found a document where it says that a gR class fast acting fuses (which mine is) are specifically designed to be able to cope with overload of 160% which gave me a peace of mind and I put the fuse back in.

[EV_Builder]

Yes; fast is relative to time. So its overload 160% won't be for very long (and or very often aka track use) and the very fast blowing (emidiate style) will be lower.