Atlas Copco GA 75+ - Dryer Faults: Pressure and Condensate Issues

• 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
= 89 A, maximum ambient temperature is 45 °C, recommended fuse = 100 A
• Single supply cables (3 phases + PE - configuration (1)):
• I = 89 A + 10 % = 89 x 1.1 = 97.9 A
• 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.
11.3 Protection settings
Setting motor overload relay (F21)
Frequency
(Hz)
Voltage (V) GA 55
F21 (A)
GA 55 P
F21 (A)
GA 75
F21 (A)
GA 75 P
F21 (A)
GA 90
F21 (A)
IEC
50 200 143 149 192 192 239
50 400 70.3 75.0 95.1 95.1 113.7
60 200 143 149 149 149 239
60 220 130 135.5 174.5 174.5 217.3
60 230 124.3 129.6 137 167 207.8
60 380 75.1 78.3 100.3 100.3 121.2
60 440 67.3 70.2 85.1 85.1 103.1
60 460 64.4 67.1 81.4 81.4 98.6
Settings for fan motor overload protection (Q15)
Frequency
(Hz)
Voltage (V) GA 55
Q15 (A)
GA 55 P
Q15 (A)
GA 75
Q15 (A)
GA 75 P
Q15 (A)
GA 90
Q15 (A)
IEC
50 200 10.6 10.6 10.6 10.6 15.4
50 400 5.3 5.3 5.3 5.3 7.7
60 200 11.6 11.6 11.6 11.6 16.5
Instruction book
192 2920 7109 60