Power Considerations; Power Requirements - Siemens SIMATIC S7-200 System Manual

Installing an S7-200 PLC
2.5

Power Considerations

The S7-200 CPUs have an internal power supply that provides power for the CPU,
the expansion modules, and other 24 VDC user power requirements. Use the
following information as a guide for determining how much power (or current) the
CPU can provide for your configuration.

Power Requirements

Each S7-200 CPU supplies both 5 VDC and 24 VDC power:
Each CPU has a 24 VDC sensor supply that can supply 24 VDC for local input
points or for relay coils on the expansion modules. If the power requirement for
24 VDC exceeds the power budget of the CPU, you can add an external
24 VDC power supply to provide 24 VDC to the expansion modules. You must
manually connect the 24 VDC supply to the input points or relay coils.
The CPU also provides 5 VDC power for the expansion modules when an
expansion module is connected. If the 5 VDC power requirements for
expansion modules exceeds the power budget of the CPU, you must remove
expansion modules until the requirement is within the power budget.
The specifications in Appendix A provide information about the power budgets of
the CPUs and the power requirements of the expansion modules.
Warning
!
Connecting an external 24 VDC power supply in parallel with the S7-200 DC
Sensor Supply can result in a conflict between the two supplies as each seeks to
establish its own preferred output voltage level.
The result of this conflict can be shortened lifetime or immediate failure of one or
both power supplies, with consequent unpredictable operation of the PLC system.
Unpredictable operation could result in death or serious injury to personnel, and/or
damage to equipment and property.
The S7-200 DC Sensor Supply and any external power supply should provide
power to different points. A single connection of the commons is allowed.
2-18
S7-200 Programmable Controller System Manual
A5E00066097-02