Liebert UPS System user manual External Power Distribution, Start up of Parallel Operation System

Chapter 8 Parallel System

8.3 External Power Distribution

Parameters such as maximum permissible input current (In is the rated input current) of each UPS, capacity of input circuit breaker(suitable for rectifier input and bypass input) are given in Table 3-5. It is recommended that the input power source of each UPS unit should be input to its own circuit breaker in the switchgear. The battery group shouldn’t be shared among the UPS units. Each UPS unit should be equipped with an output circuit breaker for the convenience of switching off the UPS during maintenance. The capacity of the output switch of the power cabinet should be selected according to the maximum capacity of the parallel operation system considering the redundancy. The specifications of the switch are given in Table 8-2.

Table 8-2 Output Power distribution parameters

Capacity of output circuit breaker			UPS capacity
		20kVA	30kVA	40kVA	60kVA
	Single module UPS system	63A	63A	100A	100A
	1+1	63A	63A	100A	100A
	2+1	125A	125A	200A	200A
Parallel	3+1	200A	200A	300A	300A
operation	4+1	250A	250A	400A	400A
modes
	5+1	300A	300A	500A	500A
	6+1	400A	400A	600A	600A
	7+1	450A	450A	700A	700A
	8 UPS units	500A	500A	800A	800A

8.4 Start up of Parallel Operation System

Check the input and output wiring of each UPS unit. Ensure that the phase rotation of the rectifier, bypass and output of each UPS unit is same. Ensure the parallel connection cables are connected firmly.

1.Switch on the UPS units one by one and check their operation states: (1)Commission each UPS unit referring to Chapter 4 for the methods.

(2)Set the parameters of each UPS unit through background host and adjust the parameters of parallel operation system.

Configuration setup: Each UPS unit should be set as “parallel” mode. The UPS unit that is connected to the background host should be set as “connect to background host”;

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