Central Controllers and Expansion Units Power Supply Units

4.4.4Operation

General Notes on the Power Supply Unit

Before placing the power supply unit in operation, please comply with the following.

SThis power supply unit does not have potential isolation between its primary and secondary circuits.

SNo voltage of more than 50 V may develop between the power supply outputs and the protective conductor of the power supply unit.

SThe protective conductor must always be connected, as must the jumper between CC rack and front plate of the power supply unit.

SIn the event of overvoltage of the internal DC supply voltages

Vo/p1 = +5 V and Vo/p3 = +15 V, the power supply unit is switched off retentively. There is a voltage of v0.5 V at Vo/p1 and Vo/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.

SYou can insert an air filter with filter holder in the bottom of the housing of the power supply unit.

SObserve the voltage level of 3.4 V and correct polarity when applying an external backup voltage.

SBefore 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.

SThe jumper from terminals UH 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.

4-64

System Manual

C79000-G8576-C199-06

Page 130
Image 130
Siemens S5-135U/155U appendix Operation, General Notes on the Power Supply Unit