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Standard conditions for current rating
The tabled values for the current rating were calculated according to IEC 287 for the following standard conditions:
Continuous operation single circuit for 3--phase current, single conductor for 1--phase current 30 °C ambient temperature and sufficiently large and ventilated
spaces, whose ambient temperature is not appreciably increased by the heat coming from the cables.
120 °C conductor temperature.
Frequency up to 200 Hz.
Installation in air, unrestricted heat dissipation, means that the following installation conditions are observed:
Distance of the cables from the wall, from the floor, from the ceiling greater than cable diameter.
Distance between two adjacent power circuits greater than 2 x cable diameter.
Vertical distance between power circuits laid one upon another for individual cables greater than 2 x cable diameter and for layers of cables > 200 mm
Perforated tray with a perforation > 30 % of the total surface.
Open trays are continuous supports with vertical sides, but without cover. A possible perforation accounts for < 30% of the total surface.
Closed ducts are entirely closed. Pipes belong to this category also. The max. filling degree is 70%.
0
De rating Factors for Deviating Ambient Temperature (Basis 30 C)
Reduction Factors for Different Conductor Temperature
Ambient
0
Temp. C
Reduction
Factor RF1
0
Conductor Temp. C
Maximum permitted typical conductor temperature for various insulation materials
according to IEC 60216 (20000 h/50 % Elongation at break)
0
Current Rating C
Wires & Cables
PVC,FRLS
XLPE & EPR(Chemical cured)
120
Siechem EBXL - XLPO
120
Material
0
Temperature C
70
20 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115
1.05 1.00 0.97 0.94 0.91 0.88 0.85 0.82 0.78 0.75 0.71 0.67 0.62 0.58 0.53 0.47 0.41 0.33 0.22
Reduction Factor RF
2
120
110
100
90
80
70
0.72
0.79
0.85
0.91
0.96
1
90
Siechem EBXL - XLPE