Liebert UPS System - Manual (Page 34)

Chapter 3 Electrical Assemble
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4. Earthing Method
The UPS rectifier source has no neutral cable. The bypass and output source have
neutral cables and the input and output neutral cables are short circuited.
The lightning protection earth PE and the protection earth of the cabinet are
connected as shown in Figure 3-5. The user can decide whether to use a
connection cable according to his earthing requirement.
PE for lightning protection
PE inside cabinet
Protective earth
Fig. 3-5 Wiring inside cabinet
Generally, the separated neutral mode is better for human safety. The united
connection mode is better for the UPS system. If there is C-level lightning
protection unit inside the UPS, the cabinet protection earth and the lightning
protection earth should be connected together.
In the bottom cable entry mode, the protection earth cable should be connected
with a copper terminal on the beam inside the cabinet or connected to the copper
busbar marked with PE. User board M8x12 to fix the cable.
Note
The leakage current of the UPS should be less than 1 ampere.
The earthing resistance of the UPS cabinet should be less than 1 ohm.
3.2.2 Signal cable
The Signal cable includes serial communication cables, control cables of
input/output contacts, logic and load sharing cables.
1. Routing the signal cable
The signal cables should be routed according to Figure 3-6