Data Sheet

QT20.241, QT20.241-C1
Q-Series
24V, 20A, THREE PHASE INPUT
Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
22.8. PARALLEL USE TO INCREASE OUTPUT POWER
Power supplies from the same series (Q-Series) can be paralleled to increase
the output power. The output voltage shall be adjusted to the same value
(±100mV) or the units can be left with the factory settings.
25/27
If more than three units are connected in parallel, a fuse or circuit breaker
with a rating of 25A is required on each output. Alternatively, a diode or
redundancy module can also be utilized.
Keep an installation clearance of 15mm (left / right) between two power
supplies and avoid installing the power supplies on top of each other. Do
not use power supplies in parallel in mounting orientations other than the
standard mounting orientation (input terminals on the bottom of the unit)
or in any other condition where a derating of the output current is required (e.g. altitude, above 60°C, …).
Unit B
-
+
Load
+
-
AC
DC
AC
DC
-
+
Unit A
Pay attention that leakage current, EMI, inrush current, harmonics will increase when using multiple power supplies.
22.9. PARALLEL USE FOR REDUNDANCY
Power supplies can be paralleled for redundancy to gain 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
power supplies in parallel. This is called a 1+1 redundancy. In case one power supply unit fails, the other one is
automatically able to support the load current without any interruption. Redundant systems for a higher power
demand are usually built in a N+1 method. E.g. five power supplies, each rated for 20A are paralleled to build a 80A
redundant system. For N+1 redundancy the same restrictions apply as for increasing the output power, see also
chapter 22.8.
Please note: This simple way to build a redundant system does not cover failures such as an internal short circuit in
the secondary side of the power supply. In such a case, the defective unit becomes a load for the other power supplies
and the output voltage can not be maintained any more. This can be avoided by utilizing redundancy modules, which
have decoupling devices (diodes or MOSFETs) included. Further information and wiring configurations can be found in
chapter 21.4.
Recommendations for building redundant power systems:
a) Use separate input fuses for each power supply. A separate source for each supply when possible increases the
reliability of the redundant system.
b) Monitor the individual power supply units. Therefore, use the DC-OK relay contact of the QT20 power supply.
c) It is desirable to set the output voltages of all units to the same value (± 100mV) or leave it at the factory setting.
22.10. INDUCTIVE AND CAPACITIVE LOADS
The unit is designed to supply any kind of loads, including capacitive and inductive loads.
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and after
a 5 minutes run-in time unless otherwise noted.
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