LV Breaker TCC 1

[Alms88]

Does Same rating MCCB from different OEM will have same trip curve

For example
OeM A : 80amps , thermal magnetic, 25ka ice,0.69ui
Other parameters

Oem B :80amps , thermal magnetic, 25ka ice,0.69ui

Will the curves of this OEMs identical ????

My doubt is actually? Does thermal curves of breakers are generic irrespective of manufacturer???

 

[davidbeach]

Similar but not identical.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Alms88]

Hi

What is meant by similar?

 

[Kiribanda]

It depends on the relevant standard.
1) All IEC MCCBs & PCBs are made for IEC 60947
2) All IEC mcbs are made for IEC60898
3) All ANSI breakers are made for UL 489

 

[Alms88]

Kiribanda sri lankan???

 

[che12345]

Dear Mr. Alms88
Q1. What is meant by similar?
A1. If you look up the IEC and UL documents as pointed out by learned Mr. Kiribanda, you would notice that the TCC is NOT a [line/curve] but a BAND. Meaning that: a) the HOT tripping time at X times rated current is acceptable to be within a-b limits. b) Likewise, the COLD tripping time at Y times rated current is acceptable to be within c-d limits, etc.....
A2. Take any OEM A and B, their breakers of similar kA and current rating, you will "see" what is meant by "similar". Their "thermal" curve characteristic is "typical/similar" of bi-metallic element. Different manufacturer may use different bi-metallic element. Hence the curve is "similar" but may NOT be [identical].
A3. Attention: The TCC tripping "band" is plotted on a [log/log scale]!
A4. It doesn't matter whether in Sri Lanka or any other locations, the breakers are likely to be manufactured in compliance with either IEC or UL Standards.
Che Kuan Yau (Singapore)

 

[Alms88]

Thank you everybody

All are rich content replies

 

[dpc]

Nearly all new MCCBs made in the US are dual-rated - UL 489 and IEC. The TCC shouldn't change for those. The "good" news is that MCCBs in series are unlikely to coordinate reliably due to the instantaneous trip requirement.