Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations JAE on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Kindly through some light on how to 2
- Thread starter Mehak kar
- Start date
-
2
- #2
davidbeach
Electrical
You don't calculate it, you read it off the nameplate. The relevant IEEE or IEC standard may then provide guidance for adjusting that rating (downward) when the prospective fault current X/R exceeds the test value.
I’ll see your silver lining and raise you two black clouds. - Protection Operations
I’ll see your silver lining and raise you two black clouds. - Protection Operations
Breaking capacity formula (does not matter what type of breaker is used).
BC = 1.732 * V * A * 10E-6
BC is breaking capacity in MVA
V is the rated service voltage in volts
A is the short circuit current in amperes
Converting energy to motion for more than half a century
BC = 1.732 * V * A * 10E-6
BC is breaking capacity in MVA
V is the rated service voltage in volts
A is the short circuit current in amperes
Converting energy to motion for more than half a century
Mehak kar (Mechanical)(OP)2 Dec 23 18:55
" Kindly through some light on how to calculate the breaking current capacity of a MCCB?"
The learned advice by Mr. davidbeach is short and sharp. A great post.
I would like to add the following for clarity, for your information.
1. In the IEC world, a) rated ultimate short-circuit breaking capacity (Icu,..is the maximum short-circuit current value which the CB can break twice (O-t-CO) at the corresponding rated operational voltage. After the opening and closing sequence, the CB is NOT required to carry the rated current.
b) Rated service short-circuit breaking capacity (Ics), ..._is the maximum short-circuit current value which the CB can break three times in accordance with a sequence of opening and closing operation (O-t-CO-t-CO) at a defined voltage of (Ie) and at a defined power factor. After the sequence, the CB is required to carry its rated current.
2. Note: a) Testing procedure and judgment differ between IEC (in Europe) and IEEE/NEMA (in US). The same CB rated X kA per IEC is very likely to be rated Y kA per IEEE/NEMA.
b) This result to test certification or EC mark in Europe is NOT automatically as being listed/recognized by UL in the US.
3. IEC in (Europe) and IEEE/NEMA (in US), each publishes/issues their own "standard" without any co-ordination or harmonisation.
4. The IEC and IEEE/NEMA do NOT carryout any testing or policing that their "standard" is correctly implemented/interpreted.
Che Kuan Yau (Singapore)
" Kindly through some light on how to calculate the breaking current capacity of a MCCB?"
The learned advice by Mr. davidbeach is short and sharp. A great post.
I would like to add the following for clarity, for your information.
1. In the IEC world, a) rated ultimate short-circuit breaking capacity (Icu,..is the maximum short-circuit current value which the CB can break twice (O-t-CO) at the corresponding rated operational voltage. After the opening and closing sequence, the CB is NOT required to carry the rated current.
b) Rated service short-circuit breaking capacity (Ics), ..._is the maximum short-circuit current value which the CB can break three times in accordance with a sequence of opening and closing operation (O-t-CO-t-CO) at a defined voltage of (Ie) and at a defined power factor. After the sequence, the CB is required to carry its rated current.
2. Note: a) Testing procedure and judgment differ between IEC (in Europe) and IEEE/NEMA (in US). The same CB rated X kA per IEC is very likely to be rated Y kA per IEEE/NEMA.
b) This result to test certification or EC mark in Europe is NOT automatically as being listed/recognized by UL in the US.
3. IEC in (Europe) and IEEE/NEMA (in US), each publishes/issues their own "standard" without any co-ordination or harmonisation.
4. The IEC and IEEE/NEMA do NOT carryout any testing or policing that their "standard" is correctly implemented/interpreted.
Che Kuan Yau (Singapore)
- Status
Similar threads
- Question
- Locked
- Helpful tip
- Locked
- Question