User manual

QS3.241
Q-Series
24V, 3.4A, SINGLE PHASE INPUT
Nov. 2006 / Rev. 1.0 DS-QS3.241-EN
All parameters are specified at 24V, 3.4A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted..
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19/21
26.7. PARALLEL USE TO INCREASE OUTPUT POWER
Power supplies can be paralleled to increase the output power.
Fig. 26-7 Schematic for parallel operation
Instructions for parallel use:
Unit A
AC
DC
Unit B
AC
DC
-
+
-
+
Load
+
-
a) Use only power supplies from the same series (Q-Series).
b) A fuse (or diode) on the output is only required if more than
three units are connected in parallel.
c) Do not load terminals with more than 25A. Follow wiring
instructions according to chapter 0
d) Keep an installation clearance of 15mm (left/right) between
two power supplies and avoid installing the power supplies
on top of each other.
26.8. PARALLEL USE FOR REDUNDANCY
Power supplies can be paralleled for 1+1 redundancy to gain a higher system availability. Redundant systems require
a certain amount of extra power to support the load in case one power supply unit fails. The simplest way is to put
two QS3.241 power supplies in parallel. In case one power supply unit fails, the other one is automatically able to
support the load current without any interruption. This simple way to build a redundant system has two major
disadvantages:
a. The faulty power supply can not be recognized. The green LED will still be on since it is reverse-powered from
the other power supply.
b. It does not cover failures such as an internal short circuit in the secondary side of the power supply. In such a -
virtually nearly impossible - case, the defective unit becomes a load for the other power supplies and the output
voltage can not be maintained any more.
This can only be avoided by utilizing decoupling diodes which are included in the decoupling module YR2.DIODE or
redundancy module YRM2.DIODE with alarm contacts.
Recommendations for building redundant power systems:
a) Use separate input fuses for each power supply.
b) Monitor the individual power supply units. A DC-ok lamp and a DC-ok contact is included in the redundancy
module YRM2.DIODE. This feature reports a faulty unit.
c) When possible, connect each power supply to different phases or circuits.
26.9. DAISY CHAINING OF OUTPUTS
Daisy chaining (jumping from one power supply output to the next) is allowed as long as the maximum current
through one terminal pin does not exceed 25A. If the current is higher, use a separate distribution terminal block.
Fig. 26-8 Daisy chaining of outputs
Fig. 26-9 Using distribution terminals
Power
Supply
+ + - -
Input
Power
Supply
+ + - -
Input
Load
+ -
max 25A!
L N PE
Power
Supply
+ +
- -
L N PE
Power
Supply
+ +
- -
Load
+ -
Distribution
Terminals