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Chapter 3 Electrical Assemble
24
protective earth cable and lightning protection earth cable, should be 0.5 times of
phase cable.
The relationship between the current and cross-sectional area is shown in Table 3-
2.
Table3-2 Recommended cross sectional area of cables
20kVA 30kVA 40kVA 60kVA
Name
Current
(A)
Cable
(mm
2
)
Current
(A)
Cable
(mm
2
)
Current
(A)
Cable
(mm
2
)
Current
(A)
Cable
(mm
2
)
Battery 56 25 84 25 112 35 168 50
Bypass 37 16 56 16 74 25 112 35
Output 37 16 56 16 74 25 112 35
Input 44 16 66 16 88 25 132 35
Neutral line 25
25
35
50
Earth cable 16
16
25
25
3.1.3 Selection of signal cables
Signal cables should use shielded multi-conductor cables. But if cable with single
conductor is used, the different cables should be bonded together to increase the
mechanical strength. The number of the bonded cables should not exceed 30. The
cross-sectional area of the cable with single conductor should be at least 0.5 sq-
mm. Serial communication cables should use 3 or 5 shielded conductor cables.
3.2 Cable connections
3.2.1 Power cables
1. Cabling layout
Cabling layout is shown in Figures 3-1 and 3-2. For single input UPS, the rectifier
input and bypass input are connected together.