Answer / mike evans

Circuit breakers are designed with withstand short circuit
currents for a short period of time, defined as Icw for a
period of 1 second. This is designed to guarantee
selectivity of breakers and other devices providing short
circuit current protection. The ultimate breaking capacity
of the breaker is the highest symmetrical short circuit
fault current that the breaker is designed to break, and the
breaker manufacture is required to guarantee this level of
performance for one time only. Ics or service breaking
capacity must be guaranteed at least 3 times.
Realistically, the value of Icu is not practical when
considering fault calculations in a distribution system, and
often manufacturers aim for achieving Ics=Icu.

Answer / ravikumar varatharaj

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
Icw - rated short-time withstand current
The rated short-time withstand current of a circuit-breaker is the value of short-time withstand
current assigned
Icm - short-circuit breaking (or making) capacity
a breaking (or making) capacity for which the prescribed conditions include a short circuit

Answer / tad rybak

To my understanding Icm stands for Short Circuit Making
Capacity.
According to standard IEC 947-2 or BS EN60947, etc.
It is equal to 2.2 x Icu, where Icu means Ultimate breaking
capacity.

Answer / sagar

plz explain with exampie i cant understand

Answer / vyara

Ultimate or rated short-circuit breaking capacity
(Icn - EN 60898)
A breaking capacity for which the prescribed conditions,
according to a specified test sequence do
not include the capability of the MCB (Miniature Circuit
Breakers) to carry 0.96 times its rated current for the
conventional time.
Ultimate short-circuit breaking capacity
(Icu - EN 60947-2)
A breaking capacity for which the prescribed conditions,
according to a specified test sequence do
not include the capability of the MCB to carry its
rated current for the conventional time.
Service short-circuit breaking capacity
(Ics - EN 60898)
A breaking capacity for which the prescribed
conditions according to a specified test sequence
include the capability of the MCB to carry 0.96
times its rated current for the conventional time.
Service short-circuit breaking capacity
(Ics - EN 60947-2)
A breaking capacity for which the prescribed
conditions according to a specified test sequence
include the capability of the MCB to carry its rated
current for the conventional time.

minimu size and length of gi earth pipe

2 Answers  

---

What is reactance, reluctance,capistance, pls give answeer in hinglish and be simply Jo asani we smajh m aa jaye

0 Answers  

---

what parameters should we check to reduce the power bill

0 Answers  

---

How could a garment factory benefit from renewable energy

0 Answers  

---

how can we change the phase angle b/w two phase?

2 Answers  

---

---

In Electrical 'Single Line Diagram' cable nomenclature shows "2 X 1C X 630sq.mm to be provided for one incomer. The question is how many cable to be proved for one Incomer.

0 Answers  

---

What will be the resultant out put voltage when two different voltage rating batteries are vconnected in parallel? pls. answer with example if available.

1 Answers  

---

Waht will happened if reactive power increase in the line? waht about active power increase too?

3 Answers  

---

Why NGR is required for 11Kv geneartor in power plant

2 Answers   AB Inc, ABB,

---

how to measure the transformer resistance values(dyn11)?and howmuch the minimum value?

0 Answers  

---

according to ohms law ,the voltage increases then current is what happened?

4 Answers   NTPC,

---

in transformers for ex. 100mva and 400kv the secondary current is about 420 amps but for selection of bushing the capacity of selected bushing is 2000A why there is such big difference ?

2 Answers   ABB,

---