Applications
5.1
Parallel connection to increase power rating
To enhance performance, two LOGO!Power power supplies of the same type can be
galvanically connected in parallel.
The following must be observed:
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● The cables connected to each power supply at terminals "+" and "-" must have identical
lengths and the same cable cross-sections (or the same impedance) up to a common
external network junction (terminal strip) if possible.
● The parallel-switched power supplies must be switched on simultaneously with a
common switch in the mains supply line (e.g. with the main switch available in control
cabinets).
● The output voltages measured in no-load operation for the power supplies that are not yet
connected in parallel should not deviate more than a maximum of 0.2 %. This usually
corresponds to the factory setting. If the output voltage is changed, you should connect
the "-" terminals and then, in no-load operation, measure the voltage difference between
the "+" terminals that have not yet been connected. The voltage difference should not
exceed 0.2%.
Figure 5-1
Parallel connection to increase power rating
CAUTION
For connection of more than two power supplies in parallel, additional measures must be
taken to prevent high backward feeding currents in the event of a secondary device fault.
For this purpose, a suitable protective circuit (e.g. decoupling diode) must be installed
between each "+" terminal of the power supply and the common connection point.
LOGO!Power
Operating Instructions, 02.2011, C98130-A7560-A999-1-7619
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SIEMENS [ Siemens Semiconductor Group ]
