Siemens S5-135U/155U appendix Basic Functions, Monitoring, Signaling

Central Controllers and Expansion Units Power Supply Units

Basic Functions	The power supply units offer the following functions:
	S	System power supply
		All the system voltages required for operation of the modules in a CC or
		EU are supplied.
	S Power supply for backup (in the CC and EU 185):
		A lithium battery or an external battery ensure data backup when the
		system voltage is switched off or fails.
		± The lithium battery remains in the CC/EU and ensures backup, even
		during replacement of the power supply unit
		± Instead of the lithium battery, an external battery can be connected for
		data backup purposes. Situated on the front plate of the power supply
		unit are two sockets to connect an external battery.
	The rechargeable battery (in the power supply) continues to back up while
	either the lithium battery or external battery is being replaced or fails,
	ensuring that no data are lost.
	S	Heat removal
		Three independent fans which are individually replaceable during
		operation remove the dissipated power. If a fan fails, the supply voltage
		for this fan is switched off and the other two fans continue operation at
		increased speed.
Monitoring	The power supply units contain monitoring functions to detect the following
Functions	faults:
	S Failure of system voltage
	S Failure of output voltages
	S Failure of an externally applied 24 V DC load voltage (voltage monitor)
	S Fan failure or inadequate air flow
	S	Lithium battery failure
	S	Rechargeable battery failure
	In this context, a voltage failure is equivalent to a drop of the monitored
	voltage below a preset limit (see Section 4.3.6 of the Technical
	Specifications).
Signaling	The failure of a monitored function is signaled by the power supply units:
Functions	S	via LED indicators on the front plate;

S via relays with which signaling circuits can be switched;

S via signals to the S5 bus.

4-20	System Manual
	C79000-G8576-C199-06