S7-200 CPU module 5VDC 24VDC power supply:
CPU when there are extension modules via the I/O bus to provide 5V power supply, 5V power consumption of all the extension modules and cannot exceed the power rating of the CPU to provide. If an external 5V power supply won’t be enough. Each CPU has a 24VDC sensor supply, it entered for the native entry point and extension modules and extension module 24VDC relay coil. CPU module power supply if power requirements exceed the fixed, you can add an external 24VDC power supply provided to the expansion module.
The so-called power calculation is to use the available power capacity of the CPU, less power consumption required for each module.
Note: EM277 module itself does not require a 24VDC power supply the power supply for the communication port used. 24VDC power supply demand depends on the load on the communications port.
The communication port on the CPU, and TD 200 can connect PC/PPI cable and power supply for them, the power consumption is no longer included in the calculation.