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AWG or kcmil Maximum current

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)):

• I = 128 A + 25 % = 128 x 1.25 = 160 A

• For AWG2/0, the maximum current is 175 A, which is sufficient => use AWG2/0

• Install the prescribed maximum fuse (150 A) on each cable

• Parallel supply cable (2 x 3 phases + 2 PE - configuration (2)):

• I = (128 A + 25%)/2 = (128 x 1.25)/2 = 80 A

• For a AWG4, the maximum current is 85 A x 0.8 = 68 A, which is insufficient. For an AWG3, the

maximum current is 100 x 0.8 = 80 A. So 2 parallel cables of 3 x AWG3 + 2 x AWG8 are sufficient.

• Install 80 A fuses on each cable.

Instruction book

2920 7110 00 113