Siemens Simatic S7-400 - Manual (Page 85)

Power Supply Modules
3-5
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Characteristics
The redundant power supply of an S7-400 has the following characteristics:
• The power supply module delivers a making current in accordance with
NAMUR.
• Each of the power supply modules can take over the supply of power to the
whole rack if the other one fails. There is no loss of operation.
• Each of the power supply modules can be exchanged while the system is in
operation. No loss of power and no peak stress occurs with the effective
voltages when the modules are removed or inserted.
• Each of the power supply modules monitors its function and sends a message if
it fails.
• Neither of the power supply modules can generate an error which affects the
output voltage of the other power supply module.
• A redundant battery concept (backup concept) is only provided when two
backup batteries are used in each of the power supply modules. If only one
battery is used in each module, only non-redundant backup is possible, since
both batteries are being used at the same time.
• The failure of a power supply module is registered via a plug and remove
interrupt (default STOP). Only if used in the second segment of the CR 2 is no
message sent if the power supply module fails.
• If two power supply modules are inserted but only one is switched on, there is a
power-up delay of up to one minute when the line voltage is switched on.
Note
The check box “Startup if preset configuration not equal to actual configuration”
should be activated in the “Properties” dialog box of the CPU.