Operation; General Notes On The Power Supply Unit - Siemens S5-155U System Manual

6ES5 955-3NA12 Power Supply Unit
4.5.4

Operation

General notes on the power
supply unit
4 - 76
Before placing the power supply unit in operation, please comply with
the notes in the following section.
• • No voltage of more than 50 V may develop between the power
supply outputs and the protective conductor of the power supply
unit.
• • The protective conductor must always be connected, as must the
jumper between CC rack and front plate of the power supply unit.
• • In the event of overvoltage of the internal DC supply voltages
U = +5 V and U = +15 V, the power supply unit is switched
A1 A3
off retentively. There is a voltage of ≤ 0.5 V at U
Off state (see Section 4.5.6, 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.
• • You can insert an air filter with filter holder in the bottom of the
housing of the power supply unit.
• • Observe the voltage level of 3.4 V and correct polarity when
applying an external backup voltage.
• • The backup battery is supplied separately and must be fitted before
startup. 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 carry out an OVERALL RESET.
• • The jumper from terminals U
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.
and U
A1
to EN will enable the power
H
System Manual
C79000-B8576-C199-03
in the
A3