MOULDED CASE CIRCUIT BREAKER (MCCB) - Standard Electricals
MOULDED CASE CIRCUIT BREAKER (MCCB) - Standard Electricals
MOULDED CASE CIRCUIT BREAKER (MCCB) - Standard Electricals
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<strong>MCCB</strong><br />
DISCRIMINATION DATA<br />
STANDARD <strong>MCCB</strong> UPSTREAM DEVICE INSTANTANEOUS TRIP SET AT HIGH<br />
SKB 0<br />
SKB 3/4<br />
SKB 1/2<br />
kA@<br />
Product Rating<br />
1250 1600<br />
1000<br />
800<br />
600<br />
800<br />
630<br />
500<br />
400<br />
315<br />
(A) 415V 25 23 40 50 63 80 100 125 160 ALL 250<br />
8000 7400 8300 9200 9200 9200<br />
6300<br />
3000 4000 5000<br />
SKB 1/2 63 25 800 800 800 1600 1600 2500<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
3000 4000 5000<br />
2500<br />
80 25 1600 1600<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
5000<br />
4000<br />
3000<br />
2500<br />
100 25 1600 1600<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
3000 4000 5000<br />
125 25 1600 1600 2500<br />
SKB 3/4<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
3000 4000 5000<br />
2500<br />
160 25<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
5000<br />
3000 4000<br />
2500<br />
200 25<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
4000 5000<br />
315 50<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
5000<br />
400 50<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
6300<br />
500 50<br />
9200<br />
9200<br />
9200<br />
8300<br />
8000 7400<br />
630 50<br />
9200<br />
9200<br />
9200<br />
8300<br />
7400<br />
800 50<br />
9200<br />
9200<br />
9200<br />
SKB 0 1000 50<br />
9200 9200<br />
1250 50<br />
9200<br />
1600 50<br />
The above table gives fault current in amperes till which level the downstream breakers shall act prior to the upstream breaker<br />
Selection & Application<br />
TRANSFORMER PROTECTION<br />
Primary side<br />
For the protection of transformer with a circuit breaker connected<br />
to the primary side (LT primary) the no load inrush current of the<br />
transformer must be considered. The peak value of the first<br />
current wave often reaches 10-15 times the rated current and<br />
may sometimes reach as high as 20-25 times. However, the<br />
transient decays very quickly (in a few m.sec.). Thus the <strong>MCCB</strong><br />
selected should have a magnetic setting which will not be<br />
actuated by the momentary inrush current.<br />
Secondary side<br />
STANDARD <strong>MCCB</strong>s can be used for protection of transformer on<br />
the LT side (secondary side) as an outgoing protective device.<br />
Selection table For Transformer Protection<br />
<strong>MCCB</strong> Rating in Amperes<br />
Transformer SKB-5 SKB-6 SKB-7 SKB-1 SKB-2 SKB-2 SKB-3 SKB-4<br />
Rating (KVA) 10kA 16kA 25kA 25kA 25kA 35kA 35kA 50kA<br />
16 25 25 25 25 25 25<br />
25 40 40 40 40 40 40<br />
63 100 100 100 100 100 100<br />
100 160 160 160 160 160<br />
160 250 250 250 250 250<br />
200 315 315<br />
250 400 400<br />
315 500 500<br />
400 630 630<br />
500<br />
630<br />
750<br />
800 800<br />
GENERATOR Set Protection<br />
STANDARD <strong>MCCB</strong>s can be used for the effective protection and<br />
control of Diesel Generating set against overload and short circuits.<br />
The Current rating of <strong>MCCB</strong> to be selected is calculated as follows :<br />
kVA = 3 U e X Ie<br />
I e = kVA<br />
3x<br />
U e<br />
or<br />
Where,<br />
kVA = Rating of the DG Set<br />
U e = Rated Voltage<br />
I e = Rated Current<br />
The <strong>MCCB</strong> rating selected is greater than or equal to the rated<br />
current value<br />
The rated current of the transformer is calculated as follows :<br />
kVA x 1000<br />
I = Amps<br />
e<br />
3 x U e<br />
‘U e’<br />
is the Rated Voltage at the LT side<br />
The Breaking capacity of the breaker for protection can be<br />
calculated as :<br />
I e<br />
I = x 10 b<br />
Z%<br />
-3 Kiloamperes<br />
Where ‘I b’<br />
is the rated breaking capacity,<br />
‘I e ’ the rated current<br />
‘Z%’ is the percentage impedance of transformer<br />
(specified by the manufacturer)<br />
Selection Table for DG Set Protection<br />
SKB-0<br />
50kA<br />
1000<br />
1200<br />
DG Set Rating (KVA) <strong>MCCB</strong> Rating (Amperes)<br />
16<br />
25<br />
25<br />
40<br />
63<br />
100<br />
10<br />
160<br />
16<br />
250<br />
20<br />
315<br />
25<br />
400<br />
31<br />
500<br />
40<br />
630<br />
63<br />
1000<br />
750<br />
1200
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