Quincy QGS 40, Instruction Book, Page: 100 / 132

Instruction book
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• Single supply cables (3 PE - configuration (1)):
• I = 128 A + 10 % = 128 x 1.1 = 140.8 A
• AWG3/0 (000), allows a maximum current of 200 A at 30 °C (86 °F).When the conductor has a
maximum temperature of 75 °C at 45 °C, the maximum current is 164 A ( 200 A * 0.82 = 164
A, see table 5A col. 3) which is sufficient.
• Fuses: 150 A
• Parallel supply cables (2 x 3 2 PE - configuration (2)):
• I = (128 A + 10 %)/2 = (128 x 1.1)/2 = 70.4 A
• For AWG2 at 45 °C (113 °F), when the conductor has a maximum temperature of 75 °C, the
maximum current is 95A * 0.82 * 0.8 = 62.3 A, which is insufficient. For an AWG1/0 (0), the
maximum current is 125 * 0.82 * 0.8 = 82 A. So 2 parallel cables of 3 x AWG1/0 + 2x AWG8
are sufficient.
• Install fuses of 80 A instead of 150 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 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 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)