MCB Energy Limiting Class

This is a time/current limiting rating...class 1,2 or 3, length of time max current rating allowed before trip....

Joules = I2 x R x t or because we know that watts = I2R

Joules = watts x seconds

Therefore we can say that :-

One Joule = one watt second

or energy = watts x seconds = I2 R t

If the resistance (R) remains constant or is very small compared with the current (I) as in the case of short-circuit current, then energy becomes proportional to I2t. Which is why the energy let-through of a protective device is expressed in ampere squared seconds and referred to as I2t...

You will see from the curves that the inverse time delay characteristic which provides overload protection is the same on all three. This is because the European Standards requires the breaker to carry 1.13 times the rated current without tripping for at least one hour and when the test current is increased to 1.45 times the rated current, it must trip within one hour, and again from cold if the last current is increased to 2.55 times the rated current the breaker must trip between 1 and 120 seconds. The inverse time delay characteristic of all MCBs claiming compliance with EN 60898 must operate within these limits.

Tanx sir, but i want to know what does the "max current rating" mean in your answer .does it mean 6A for a c6 Mcb or does it mean the 10KA. also i still did not fully get your point of time.does the 3 mean 3second tripping time. or does it simply mean : i2t=3

Do you get the feeling this guy is in way over his head, again?

lol, well it takes time to learn everything, one can only hope he's young enough to have the time left it will take....

Haha.what is 3 dear lyn. i think 1+2=3 ,wow ,all limiting classes "equilized".

coolyaar, you must have the hide of a rhinoceros. You can't see that SolarEagle has given you a very good and to my mind a reasonably simple explanation considering the complexity of the question.

Please find a new occupation, for the sake of our sanity!

Lot of people get exposed when it comes to basic. i read a quote (source forgotton), "the more we know the more stupid we become". google it for source.

You know how to use Google? That surprises me, you never use it!

In your case I would use another analogy, "the less we know the more dangerous we become".

What is your job title in the company that employs (tolerates) you? You seem totally incompetent in any field you have brought to this board.

For the sake of humanity please find a new occupation!

Oh tanx 4 advice.i think i should find another job 4 me.so from now on,i will post a lot of questions on this forum untill i become a GURU.i think that will be the best title for an incompetent man ,say like me. right?

MCB limiting energy class is defined in the standard EN60898-1 annex Za.

This standard gives the maximum i²t value that is allowed to flow through the circuit breaker. These values depend on the rated current of the CB, its tripping curve, and of its short circuit breaking capacity.

Most major manufacturers (Schneider, ABB, Siemens, ...) produce only class 3 MCBs , which is the class limiting the most.

I attach the tables for your info, in French only this is what I could put my hands on but I think the figures should be understandable ...

Dear Friend.

The above information is really very useful for me. I have the complete standard of iec60898-1{ed1.2}. However, I cannot find the above mentioned table. Could you please advise in which page I can refer that table.

Thank you!