Siemens S5-135U/155U - Manual (Page 130)

4-64
System Manual
C79000-G8576-C199-06
4.4.4 Operation
Before placing the power supply unit in operation, please comply with the
following.
S
This power supply unit does not have potential isolation between its
primary and secondary circuits.
S
No voltage of more than 50 V may develop between the power supply
outputs and the protective conductor of the power supply unit.
S
The protective conductor must always be connected, as must the jumper
between CC rack and front plate of the power supply unit.
S
In the event of overvoltage of the internal DC supply voltages
V
o/p1
= +5 V and V
o/p3
= +15 V, the power supply unit is switched off
retentively. There is a voltage of
v0.5 V at V
o/p1
and V
o/p3
in the Off
state (see Section 4.4.6, Technical Specifications, for overvoltage
shutdown).
The storage flip-flop is reset by switching the external supply voltage off
and on again, and the power supply unit is again operational if the
overvoltage was not the result of an internal fault.
S
You can insert an air filter with filter holder in the bottom of the housing
of the power supply unit.
S
Observe the voltage level of 3.4 V and correct polarity when applying an
external backup voltage.
S
Before startup, a lithium backup battery must be fitted or an external
backup battery with a voltage level of 3.4 V DC must be connected.
Without a backup battery, the programmable controller will remain in the
Stop state when system voltage has been switched on. The backup battery
must be fitted for startup. Press the RESET button, then perform an
OVERALL RESET.
S
The jumper from terminals U
H
to EN will enable the power supply. You
can lock out the PLC in the event of a fault by means of suitable circuitry
between the monitoring outputs and the EN inputs.
General Notes on
the Power Supply
Unit
Central Controllers and Expansion Units Power Supply Units