Time Current Curves of Various MCBs and MCCBs

[Cookie]

Does anyone have a link to various time current curves relevant to UK MCBs and MCCBs in the 16-1,200 amp range? Specifically, how many times the handle rating does it take for each to trip at 10, 5 and 1 second.

 

[DefyG]

Best consult manufacturers data. Be surprised to find one link/chart to cover all makes/sizes.

 

[Rockingit]

As soon as you go beyond 125A kind of area you're usually into specific manufacturers data, although a rough rule of thumb would be the BS / EN series as well.

 

[Cookie]

Any links or PDFs? I can get US trip curves online, EU not so much since I don't know where to look.

 

[pc1966]

UK MCBs are pretty much standardised with B (3-5 In), C (5-10), and D (10-20) curves in use. However, C and more certainly D, are generally not in domestic use.

EU also has K (sub-set of C/D at 8-12 In) and Z curves (2-3 In, so below B curve)

MCCB are very much a law unto themselves so it is manufacturer specific and frequently device set-up specific as well.

Some MCCB ranges have the "instant" magnetic trip at a fixed point, say 600A and so 16-125A or whatever all have different ratios of continuous-to-instant trip (I think this is more like the USA style of breakers).

Others have fixed (or near-fixed) ratio rather like MCBs over the model's range of In values. As some mid-range MCCB allow the thermal trip to be set over a modest range, you can slightly vary the ratio of continuous-to-instant due to an adjustable 'continuous' setting.

Other high-end MCCB have both a fixed energy-limiting magnetic trip quite high up (say 2kA), and an adjustable near-instant trip done by electronics to allow protection levels to be matched to cable adiabatic limits, selectivity with with down-stream MCBs, etc.

 

[pc1966]

This link is for the Hager UK commercial catalogue (13BM download):

https://assets.sc.hager.com/uk/-/media/Project/HagerDeep/United-Kingdom/Hager/B2B/Products/Catalogues-and-brochures/PDF_Brochures-and-docs/Product-catalogues/Hager-Commercial-Distribution-Catalogue-1220.pdf?la=en-GB

Page 98 has the typical MCBs curves, page 130 the "x160" range of MCCB, and page 137 the "x250" MCCB range. Then the tables of cascade/selectivity stuff.

Schneider has a much bigger range of MCCB but as I am not using them I simply don't have the will to try and find the documentation!

 

[Cookie]

Nice, thank you for this!

Do larger MCBs and MCCBs have similar curves?

4.5 times for 10 seconds, 6 times for 5 seconds and 10-20x for 1 second.

 

[pc1966]

Nice, thank you for this!

Do larger MCBs and MCCBs have similar curves?

4.5 times for 10 seconds, 6 times for 5 seconds and 10-20x for 1 second.

They will be "similar" in the sense the time constants, etc, are engineered to protect typical PVC/XLPE style cable insulation, but not identical. However, I would expect them to be no more than a few times different in terms of time for a given thermal overload ratio.