Atlas Copco GA 11+ Instruction Book page 136

• The table for B2 and ambient temperature = 45 ° C allows a maximum current of 93 A
for a 50 mm² cable. For a cable of 70 mm², the maximum allowed current is 118 A,
which is sufficient. Therefore, use a 3 x 70 mm² + 35 mm² cable.
If method C is used, 50 mm² is suffficient. (35 mm² for method F) => cable 3 x 50 mm²
+ 25 mm².
• Parallel supply cable (2 x 3 phases + PE - configuration (2)):
• I = (89 A + 10 %)/2 = (89 x 1.1)/2 = 49 A
• For a cable of 25 mm², B2 at 45 °C, the maximum current is 63 A x 0.8 = 50.4 A. So 2
parallel cables of 3 x 25 mm² + 25 mm² are sufficient.
• Install 50 A fuses on each cable instead of 100 A.
Cable sizing according UL/cUL
Calculation method according UL 508A, table 28.1 column 5: allowable ampacities of insulated
copper conductors (75 °C (167 °F)).
Maximum allowed current in function of the wire size
AWG or kcmil
10
8
6
4
3
2
1
1/0
2/0
3/0
Calculation method for UL:
• Single supply cables (3 phases + 1 PE - configuration (1)):
• Add 25 % to the total current from the tables (see UL 508A 28.3.2: "Ampacity shall
have 125 % of the full load current")
• Install the prescribed maximum fuse on each cable
• Parallel supply cable (2 x 3 phases + 2 PE - configuration (2)):
• Add 25 % to the total current from the tables and divide by 2
• Multiply the ampacity of the cables with 0.8 (see UL 508A table 28.1 continued)
• Install fuses of half the size of the recommended maximum fuse size on each cable.
• When using 2 x 3 phase + 2 PE as in (3):
• Add 25 % to the total current from the tables and divide by √3
• Multiply the ampacity of the cables with 0.8 (see UL 508A table 28.1 continued)
• Fuse size: the recommended maximum fuse size divided by √3 on each cable.
• Size PE cable:
• For supply cables up to AWG8: same size as the supply cables
• For supply cables larger than AWG8: use maximum allowed ampacity of the selected
supply cables and compare with value in table below (see CEC Part 1 table 17)
134
Maximum current
< 30 A
< 50 A
< 65 A
< 85 A
< 100 A
< 115 A
< 130 A
< 150 A
< 175 A
< 200 A
Instruction book
2920 7118 31