Siemens Simatic M7-400 Reference Manual page 95

The following power supply modules will switch off in the event of a short circuit or
overload after 1 s to 3 s. The module will try to restart after no more than 3 s. If the
error has been eliminated by then, the module will start up. This applies to the
following modules:
PS 405 4A
PS 405 10A
PS 405 10A R
PS 405 20A
Overload at 24 V
In the event of overload at 24 V the output current is electronically limited to a value
between 100% and 150% of the rated value. If the voltage then goes below the
undervoltage threshold of 19.2 V (–0/+ 5% corresponds to 19.2 V to 20.16 V), the
modules respond as follows:
• In the case of power supply modules with 4 A/0.5 A output current, the 24 V
voltage is disconnected and reconnected at a repeat rate of approx. 0.5 s to 1 s
until there is an output voltage that exceeds the undervoltage threshold.
• In the case of power supply modules with 10 A/1 A or 20 A/1 A output current,
the voltage depends on the load impedance, and the module runs in
characteristic curve mode.
After the overload has been eliminated, the voltage returns to the rated range and
the green 24 V LED flashes. The CPU sets the EXTF LED (external fault) and
saves the fault in the diagnostic buffer. You can trigger other responses, such as
CPU STOP or a message to a control room, in OB 81 (power supply error). If OB
81 is not parameterized, the CPU continues as normal.
Overload at 5 V
In the event of an overload at 5V, the power supply modules with 10 A or 20 A
output current can retain an output current of 16 A or 26 A for 300ms. The power
supply modules with 4 A output current can retain an output current of 8 A for 300
ms. The CPU will then go to DEFECT afterwards. If the LED DC 5 V flashes on the
power supply and is resettable with the FMR button, you will be able to perform a
restart. The CPU will remain in STOP afterwards and will then require a memory
reset.
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
(6ES7405-0DA01-0AA0)
(6ES7405-0KA01-0AA0)
(6ES7405-0KR00-0AA0)
(6ES7405-0RA01-0AA0)
Power Supply Modules
PS 407 4A (6ES7407-0DA01-0AA0)
PS 407 10A (6ES7407-0KA01-0AA0),
release ≥5
PS 407 10A R (6ES7407-0KR00-0AA0),
release ≥7
PS 407 20A (6ES7407-0RA01-0AA0)
3-15