Datasheet

PRELIMINARY
UB20.241
U–Series
24V, 20A, DC-UPS
27.5. CONNECTION OF AN EXTERNAL TEMPERATURE SENSOR
The end of charge voltage of VRLA batteries depends on the environmental temperature. This affects the lifetime of
the batteries. To avoid overcharging at higher temperatures the end of charge voltage should be adapt to the
environmental temperature. For temperature compensated battery charging it is necessary to connect an external
temperature sensor (PT1000) to the DC-UPS. PULS battery modules are equipped with an internal temperature sensor
already. A list of recommend temperature sensors is available on the PULS website if own batteries will be used.
The end of charge voltage is set to a fixed value of 13.4V if no temperature sensor is connected.
27.6. OUTPUT CIRCUIT BREAKERS
Standard miniature circuit breakers (MCB’s or UL 1077 circuit breakers) are commonly used for AC-supply systems and
may also be used on 24V branches.
MCB’s are designed to protect wires and circuits. If the ampere value and the characteristics of the MCB are adapted
to the wire size that is used, the wiring is considered as thermally safe regardless of whether the MCB opens or not.
To avoid voltage dips and under-voltage situations in adjacent 24V branches which are supplied by the same source, a
fast (magnetic) tripping of the MCB is desired. A quick shutdown within 10ms is necessary corresponding roughly to
the ride-through time of PLC's. This requires power supplies with high current reserves and large output capacitors.
Furthermore, the impedance of the faulty branch must be sufficiently small in order for the current to actually flow.
The best current reserve in the power supply does not help if Ohm’s law does not permit current flow. The following
table has typical test results showing which B- and C-Characteristic MCBs magnetically trip depending on the wire
cross section and wire length.
Fig. 27-8 Test circuit
Maximal wire length*) for a fast (magnetic) tripping:
0.75mm
2
1.0mm
2
1.5mm
2
2.5mm
2
C-2A
C-3A
C-4A
C-6A
C-10A
C-13A
B-6A
B-10A
B-13A
MCB
DC-UPS
Input
+
DC
-
Load
+
-
S1
Wire length
S1… Fault simulation switch
B-16A
27.7. TROUBLESHOOTING
The LEDs on the front of the unit and relay contacts indicate about the actual or elapsed status of the DC-UPS. Please
see also chapter 14.
The following guidelines provide instructions for fixing the most common failures and problems. Always start with
the most likely and easiest-to-check condition. Some of the suggestions may require special safety precautions. See
notes in section
25 first.
“Error” LED is flashing Check input and buffer voltage (input voltage must be typically 0.8V higher than
buffer voltage)
September 2012 / Rev. 1.3 DS-UB20.241-EN preliminary
All parameters are specified at an input voltage of 24V, 20A output load, 25°C ambient and after a 5 minutes run-in time
unless otherwise noted. It is assumed that the input power source can deliver a sufficient output current.
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