c

1. Sec2 25
Commercial and industrial solutions for 3 phase distribution
Energy let through 2
I2
t Energy let through
The energy let through by a
breaker determines the
minimum size of the
downstream cable.
Minimum cable size required based on I2
t let through energy of breaker and cable value k=115
Maximum prospective 2 4 5 6 10 15 20 25 30 36 50 65 70 100
fault level in kA
MCB’s
SQO 3/6A 1 1 1 1 - - - - - - - - - -
SQO 10A 1 1.5 1.5 1.5 - - - - - - - - - -
SQO 16/20/25A 1 1.5 1.5 1.5 - - - - - - - - - -
SQO 32/40A 1 1.5 1.5 2.5 - - - - - - - - - -
SQO 50/63A 1.5 1.5 2.5 2.5 - - - - - - - - - -
KQ 6A 1 1 1 1 1 1.5 - - - - - - - -
KQ 10A 1 1.5 1.5 1.5 2.5 2.5 - - - - - - - -
KQ 16/20/25A 1 1.5 1.5 1.5 2.5 2.5 - - - - - - - -
KQ 32/40A 1 2.5 2.5 2.5 2.5 2.5 - - - - - - - -
KQ 50/63A 1.5 2.5 2.5 2.5 2.5 4 - - - - - - - -
KQ 80A 1.5 2.5 2.5 2.5 4 4 - - - - - - - -
KQ 100A 2.5 2.5 2.5 4 4 4 - - - - - - - -
MCCB’s
CDAE/CDLE up to 100A 6 6 6 6 6 6 6 6 - - - - - -
CNAE/CNLE up to 250A 10 10 10 10 10 10 10 10 10 10 - - - -
CHAE/CHLE up to 250A 10 10 10 10 10 10 10 10 10 10 10 - - -
SLA/SLAL up to 400A 16 16 16 35 35 35 35 50 50 50 - - - -
DHLE up to 630A 16 16 16 16 16 16 16 16 16 16 16 - - -
LI/LCL/LIL up to 600A 10 10 10 10 10 10 16 16 16 16 16 16 16 16
SNA/SNAL up to 1250 50 50 50 50 50 50 50 70 70 70 70 - - -
SMA/SMAL/SMHL up to 1000A 25 25 25 25 25 25 25 35 35 70 70 - - -
PA/SPA/SPH up to 2000A 50 50 50 50 50 50 50 70 70 70 70 - - -
Table 31
Current limiting circuit
breakers let through less
energy, therefore the cable
sizes are not an indication of
continuous current ratings.
SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 25

2. Sec2 27
Commercial and industrial solutions for 3 phase distribution
Cascading - Square D MCCB/MCB 2
Cascading chart
Cascading permits the
installation of a circuit breaker
having a breaking capacity
lower than the prospective at
its point of installation. The
upstream breaker, which must
have the required breaking
capacity, limits the fault
current to that which may
safely be interrupted by the
downstream breaker. In the
case of a high fault current
both breakers may operate.
For example: a LoadCentre KQ
breaker rated at 10kA may be
used at a point in the network
having a prospective fault
current of 40kA provided that
it is protected by a CH
breaker rated 100A (50kA).
Upstream breaker
Downstream breaker
Ref
Rating
Icu
6kA
6kA
10kA
25kA
36kA
36kA
CD
100A
25kA
25
25
25
CN
100A
36kA
25
25
25
36
CN
250A
36kA
30
36
CH
100A
50kA
40
50
50
CH
250A
50kA
30
50
50
SLA
400A
36kA
36
DH
630A
50kA
50
50
SMAL
1000A
50kA
36
50
50
SPAF
2000A
50kA
36
50
50
Reference
SQO
DOM
KQ
CD
CN
SLA
Rating
3 - 63A
3 - 50A
3 - 63A
100A
250A
400A
Table 32
SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 27

3. Sec2 39
Commercial and industrial solutions for 3 phase distribution
LoadCentre KQ industrial MCB performance figures 2
Type B MCB’s
Rating (A) Zs ohm @ 230V ac R2
5s 0.4s ohms
3 15 15 3.33
6 8 8 1.67
10 5 5 1.00
16 3 3 0.63
20 2.3 2.3 0.50
25 1.8 1.8 0.40
32 1.4 1.4 0.31
40 1.2 1.2 0.25
50 0.9 0.9 0.20
63 0.73 0.73 0.16
Type C MCB’s
Rating (A) Zs ohm @ 230V ac R2
5s 0.4s ohms
6 8 4 1.67
10 5 2.3 1.00
16 3 1.4 0.63
20 2.3 1.2 0.50
25 1.8 0.9 0.40
32 1.4 0.7 0.31
40 1.2 0.6 0.25
50 0.9 0.5 0.20
63 0.73 0.37 0.16
Table 47
Earth loop impedance values.
Type D MCB’s
Rating (A) Zs ohm @ 230V ac R2
5s 0.4s ohms
6 8 2.7 1.67
10 5 1.6 1.00
16 3 1.0 0.63
20 2.3 0.8 0.50
25 1.8 0.7 0.40
32 1.4 0.5 0.31
40 1.2 0.4 0.25
50 0.9 0.3 0.20
63 0.73 0.26 0.16
Type C 80 and 100A MCB’s
Rating (A) Zs ohm @ 230V ac R2
5s 0.4s ohms
80 0.58 0.29 0.13
100 0.46 0.23 0.10
Table 48
SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 39