Liebert UPS System - Manual (Page 105)

Chapter 8 Parallel System
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This figure only shows the connection method of control cables of parallel operation
system with 3 UPS units. The others can be done according to the same methods.
Emergency stop button
1 2 3 4
1 2 3 4
1 2 3 4
Fig. 8-6 Emergency shutdown button
Where, “1”-Normally closed contacts for emergency shutdown
“2”- Central contacts for emergency shutdown
“3”- Normally open contacts for emergency shutdown
“4”- Normally closed contacts for common alarm
8.5.6 Fault and Fault Process Methods
The faults of single module UPS system is given in Chapter 7. The faults that
specially belong to the parallel operation system are given in Table 8-3. If some
UPS unit has fault, it can exit the system and other units can maintain the normal
operation mode. But redundancy is not available, so the faulty UPS unit must be
repaired as soon as possible.