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(3) Capacity control over group of modules
[Capacity control at low loads]
At low loads, the module controller increases or decreases the number of active modules to maintain the
balance between high-efficiency operation using as many heat exchangers as possible and the flow rates of
the modules for pump control.
In the medium-to-high load region, the module controller controls the operation frequency to adjust the
amount of feed water from the pumps and the compressor operation capacities according to the load.
Compressors and pumps
Unit count and frequency control
[Increasing the capacity at startup]
The module controller determines the number of modules to be operated simultaneously according to the flow
rate required by the load side. At high loads (i.e., when a high flow rate is necessary), all modules are started at
the same time; in this case, all the modules activate their respective first compressor at the same time and then
the second to fourth compressors at the same time. At these stages, the compressors maintain the operation at a
constant frequency for a fixed time of period, going up to the maximum performance eventually.
All compressors increase
operation frequency.
The first compressor increases
operation frequency and all other
compressors start.
* 1
All modules start the
first compressor.
*1 After start-up, compressors are held at a constant frequency for a given time.
Low
System
Compressors and pumps
Frequency control
8
7
6
5
4
3
2
Module 1
load
Maximum performance
Module 1
- 49 -
Capacity, flow rate
(Sum of active modules)
8
7
6
Capacity and flow rate
5
(Sum of active modules)
4
3
2
Time
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