Atlas Copco GA 30+

• Add 10 % to the total compressor current (I
tot
Pack or I
tot
FF 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 compressor current (I
tot
Pack or I
tot
FF 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:
• For supply cables up to 35 mm²: same size as supply cables
• 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: I
tot
= 234 A, maximum ambient temperature is 45 °C, recommended fuse = 315 A
• Single supply cables (3 phases + PE - configuration (1)):
• I = 234 A + 10 % = 234 x 1.1 = 257.4 A
• The table for method F, 70 °C cable temperature and ambient temperature of 45 °C allows
a maximum current of 323 A for a 185 mm² cable. So use a 3 x 185 mm² + 95 mm² cable.
• If the table for method F, 90 °C cable temperature and ambient temperature of 45 °C is
used, 120 mm² is sufficient. So a single cable 3 x 120 mm² + 70 mm² is sufficient .
• Parallel supply cable (2 x 3 phases + PE - configuration (2)):
• I = (234 A + 10 %)/2 = (234 x 1.1)/2 = 128.7 A
• Install 160 A fuses on each cable instead of 315 A.
• For a cable of 95 mm², method F, 70 °C cable temperature and ambient temperature of 45
°C, the maximum current is 209 A x 0.8 = 167.2 A. So 2 parallel cables of 3 x 95 mm² +
50 mm² are sufficient.
• For a cable of 95 mm², method F, 90 °C cable temperature and ambient temperature of 45
°C, the maximum current is 233 A x 0.8 = 186.4 A. So 2 parallel cables of 3 x 70 mm² +
35 mm² are sufficient.
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 Maximum current
10 < 30 A
8 < 50 A
6 < 65 A
4 < 85 A
3 < 100 A
2 < 115 A
1 < 130 A
1/0 < 150 A
2/0 < 175 A
3/0 < 200 A
Calculation method for UL:
• Single supply cables (3 phases + 1 PE - configuration (1)):
Instruction book
172 2920 7180 30