Rated short-circuit making current
Rated short-circuit making current
(OP)
Can any body please tell me what does (Rated short-circuit making current) stands for? E.g Rated short circuit breaking capacity is 25kA, while the Rated short circuit making capacity is 62.5kA,
Regards
Regards






RE: Rated short-circuit making current
The carry capacity is typically a I^2T function and the ability to disapate heat and remain below the melting tempenture.
The interrupting rating is the ability of the main contacts to handle the arc interrupting on the current for one operation. If the breaker is expected to interrupt a fault more than once between contact replacments it needs to have a greater interrupting rating to allow for the contact wear factor.
Also you will find there should be an additional rating called the capacitor switching rating, which is a measure of the contact speed and opening distance and the ability to operate with near 90 degree angular difference between the current and voltage.
Probally to much information, but I sometimes can't stop in mid stream.
RE: Rated short-circuit making current
RE: Rated short-circuit making current
Yep, but it was a good description.
"Probally to much information, but I sometimes can't stop in mid stream."
Pfizer makes a pill for that
RE: Rated short-circuit making current
davidbeach What do you mean by "offset"?
Thanks
RE: Rated short-circuit making current
RE: Rated short-circuit making current
The IEC standard refers to the peak value of the off-set current waveform 0.5 cycle after fault inception.
IEC 62271-100 Clause 4.103
At 50Hz, and time-constant of 45mSec
"rated short-circuit making current" = 2.5 x rated breaking current.
Your quoted "rated short-circuit making current" / "rated short-circuit breaking" currents of 62.5kA / 25kA or a ratio of 2.5 suggest an IEC breaker.
The ANSI standard refers to the first cycle rms asymmetrical current. Pre 1965 terminology was "momentary rating", now "Close and Latch Capability".