Product Manual

Table Of Contents
Maximum allowed current in function of the ambient temperature for installation method F
Ambient temperature
Cable section 30 °C 40 °C 45 °C 50 °C 55 °C
25 mm² < 110 A < 96 A < 87 A < 78 A < 67 A
35 mm² < 137 A < 119 A < 108 A < 97 A < 84 A
50 mm² < 167 A < 145 A < 132 A < 119 A < 102 A
70 mm² < 216 A < 188 A < 171 A < 153 A < 132 A
95 mm² < 264 A < 230 A < 209 A < 187 A < 161 A
120 mm² < 308 A < 268 A < 243 A < 219 A < 188 A
Calculation method for IEC:
Single supply cables (3 phases + PE - configuration (1)):
Add 10 % to the total current (I
tot
from the tables)
Install the prescribed fuse on each cable
Parallel supply cable (2 x 3 phases + PE - configuration (2)):
Add 10 % to the total current (I
tot
from the tables) and divide by 2
Multiply the ampacity of the cables with 0.8 (see table A.52.17 (52-E1))
Install fuses of half the size of the recommended maximum fuse size on each cable.
When using 2 x 3 phases + PE as in (3):
Add 10 % to the total current (I
tot
from the tables) and divide by √3
Multiply the ampacity of the cables with 0.8 (see table A.52.17 (52-E1))
Fuse size: the recommended maximum fuse size divided by √3 on each cable.
Size of the PE cable: use following rule of thumb:
For supply cables up to 16 mm²: same size as supply wires
For supply cables between 16 mm² and 35 mm²: 16 mm²
For supply cables larger than 35 mm²: half the size of the supply wires
Always check the voltage drop over the cable (less than 5 % of the nominal voltage is
recommended)!
Example: For SF 11 FF 380 V 60 Hz IEC, I
tot
= 30 A, ambient temperature is 40 °C,
recommended fuse: maximum 40 A
In case of single supply cables (3 phases + PE - configuration (1)):
I = 34 A + 10 % = 34 x 1.1 = 37.4 A
The table for installation method B2 allows a maximum current of 30 A for a 6 mm²
cable at 40 °C ambient temperature. For a cable of 10 mm², the maximum allowed
current is 40 A, which is sufficient. Therefore, use a 3 x 10 + 10 mm² cable.
If method C is used, 6 mm² is also insufficient (maximum 36 A at 40 °C). Use a 3 x 10 +
10 mm² cable.
Install 40 A fuses.
In case of parallel supply cables (2 x 3 phases + PE - configuration (2)):
I = (34 A + 10 %)/2 = (34 x 1.1)/2 = 18.7 A
For a cable of 4 mm² and installation method B2, the maximum allowed current is 23 A
x 0.8 = 18.4 A at 40 °C. So take 2 parallel cables of 3 x 6 + 6 mm².
In case of installation method C, the maximum current of a 4 mm² cable at 40 °C is 28
A x 0.8 = 22.4 A. 2 parallel cables of 3 x 4 + 4 mm² will be sufficient.
Install 20 A fuses on each cable.
Instruction book
2920 7140 42 95