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difference between Icu & Ics.

Created by: kinjalpatel1899 at: 7/4/2013 7:13 PM (17 Replies)

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7/4/2013 7:13 PM	Rate (2)
kinjalpatel1899 Posts: 61 Rating: (15)	hello, i want to know what is thedifference between Icu(ultimate short-circuit breaking capacity) & Ics (service short-circuit breaking capacity) for any circuit breaker?
kinjalpatel1899 Posts: 61 Rating: (15)
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7/4/2013 8:59 PM	Rate (0)
Ayman Elotaify Diamond Member Joined: 5/28/2008 Last visit: 12/25/2025 Posts: 4522 Rating: (843)	kinjalpatel1899 hello, i want to know what is thedifference between Icu(ultimate short-circuit breaking capacity) & Ics (service short-circuit breaking capacity) for any circuit breaker? Hello, I found these two short *.pdf files which will help you alot: https://a248.e.akamai.net/cache.automation.siemens.com/dnl/TE0MjU4NwAA_24489735_FAQ/PD_Guide_71.pdf & http://selink.schneider-electric.com.sg/selink/sg/Schinternetnew.nsf/($All)/7BC1A412C502416C48256FBA002C1D15/$file/Vol%202.%20The%20Controversy%20of%20Icu%20and%20Ics.pdf Hope this helps.
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7/5/2013 6:29 AM	Rate (2)
jeet2907 Posts: 235 Rating: (52)	Dear Mr.kinjal Hear is your answer, Icu is really the maximum perspective fault which a circuit breaker can clear (with the fault current being expressed as rms for ac). This is verified by testing in accordance with the standard and is applicable at a specific set of electrical and environmental conditions. If these conditions change then it may be necessary to derate the circuit breaker. After clearing a fault the circuit breaker does not have to remain serviceable and could be dangerous to operate. This point is particularly important in circuit breakers when the Ics is lower than the Icu. Ics is the maximum perspective fault current which the circuit breaker can clear and still remain serviceable. The standard does allow some minor welding of the contacts to take place, so after a large fault it would still be necessary to inspect the breaker. When specified as a percentage of Ics, the standard proposes ranges of 25%, 50%, 75% and 100%. I hope you got your answer.
jeet2907 Posts: 235 Rating: (52)
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7/5/2013 6:47 AM	Rate (3)
Jason85 Posts: 39 Rating: (9)	heyy, Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate breaking capacity. The breaker can break this fault current, but it may not be usable afterwards. Ics - service breaking capacity. As per Icu, but the breaker remains usable. cu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf
Jason85 Posts: 39 Rating: (9)
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7/5/2013 8:08 AM	Rate (0)
Ayman Elotaify Diamond Member Joined: 5/28/2008 Last visit: 12/25/2025 Posts: 4522 Rating: (843)	chet heyy, Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate breaking capacity. The breaker can break this fault current, but it may not be usable afterwards. Ics - service breaking capacity. As per Icu, but the breaker remains usable. cu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Hello, Icu: The breaker must be able to break this current two times without causing damage. The breaker must be changed or testest after two short circuit @ Icu Ics: The breaker must be able to break this current three times without causing damage. The breaker must be able to conduct its rated current without maintenance.
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7/5/2013 10:45 AM	Rate (1)
Valli Posts: 262 Rating: (45)	Hi, as per IEC 60947 Rated ultimate short-circuit breaking capacity (Icu) The rated ultimate short-circuit breaking capacity of a circuit-breaker is the value of ultimate short-circuit breaking capacity assigned to that circuit-breaker by the manufacturer for the corresponding rated operational voltage, under the conditions specified in standards. It is expressed as the value of the prospective breaking current, in kA (r.m.s. value of the a.c.component in the case of a.c.). Test sequence III : O - t - CO ( open - 3mins- close open) Rated service short-circuit breaking capacity (Ics) The rated service short-circuit breaking capacity of a circuit-breaker is the value of service short-circuit breaking capacity assigned to that circuit-breaker by the manufacturer for the corresponding rated operational voltage, under the conditions specified in standards. It is expressed as a value of prospective breaking current, in kA, corresponding to one of the specified percentages of the rated ultimate short-circuit breaking capacity. *It may be expressed as a % of Icu (for example Ics = 50 % Icu).* Test sequence II : O - t - CO - t - CO ( open - 3mins- close open-3mins- close open)
Valli Posts: 262 Rating: (45)	Last edited by: Valli at: 7/5/2013 10:47 AM
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7/5/2013 12:02 PM	Rate (1)
@nkur Posts: 202 Rating: (16)	Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously. Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously
@nkur Posts: 202 Rating: (16)
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7/11/2013 1:31 PM	Rate (1)
muffi Posts: 95 Rating: (10)	kinjalpatel1899 hello, i want to know what is thedifference between Icu(ultimate short-circuit breaking capacity) & Ics (service short-circuit breaking capacity) for any circuit breaker? hi kinjalpatel1899 check out this pdf Attachment The Controversy of Icu and Ics.pdf (4570 Downloads)
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7/17/2013 1:15 PM	Rate (0)
@nkur Posts: 202 Rating: (16)	chet heyy, Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate breaking capacity. The breaker can break this fault current, but it may not be usable afterwards. Ics - service breaking capacity. As per Icu, but the breaker remains usable. cu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Hi There It means that if I use a breaker of 55kA breaking capacity than Ics is 55kA & current beyiund 55kA is ICU........ please clarify also further elaborate....
@nkur Posts: 202 Rating: (16)
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7/17/2013 3:03 PM	Rate (0)
Ayman Elotaify Diamond Member Joined: 5/28/2008 Last visit: 12/25/2025 Posts: 4522 Rating: (843)	@nkur chet heyy, Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate breaking capacity. The breaker can break this fault current, but it may not be usable afterwards. Ics - service breaking capacity. As per Icu, but the breaker remains usable. cu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Icu - ultimate short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence do not include the capability of the circuit-breaker to carry its rated current continuously Ics - service short-circuit breaking capacity a breaking capacity for which the prescribed conditions according to a specified test sequence include the capability of the circuit-breaker to carry its rated current continuously - See more at: http://myelectrical.com/notes/entryid/101/understanding-lv-circuit-breaker-fault-ratings#sthash.zpVFNHp6.dpuf Hi There It means that if I use a breaker of 55kA breaking capacity than Ics is 55kA & current beyiund 55kA is ICU........ please clarify also further elaborate.... Dearnkur, Breaker manufacture should tell you this info. It should be in the breaker data sheet.
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