• 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 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)):
• 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)
< 100 A: use AWG8
< 200 A: use AWG6
< 300 A: use AWG4
Always check the voltage drop over the cable (less than 5 % of the nominal voltage is
recommended).
Example of supply cable calculation: I
tot
= 128 A, maximum ambient temperature is 45 °C,
recommended fuse = 150 A
• Single supply cables (3 phases + 1 PE - configuration (1)):
Instruction book
2920 7110 05 109
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