Siemens S7-400 Choosing the Power Supply Module, Estimating the Power Requirement, Module Total

Wiring the S7-400

4.2Choosing the Power Supply Module

Estimating the Power Requirement

You should make an estimate of the power requirement for each rack of your

S7-400 system in order to select the appropriate power supply module for the rack. Current consumption and power dissipation of the individual modules can be found in the relevant data sheets.

Calculation Example

The following modules are to be fitted in a CR with 18 slots:

•1 CPU 414-1

•3 analog input modules SM 431;AI 16 x 16 bits

•5 digital input modules SM 421;DI 32 x 24 VDC

•6 digital input modules SM 422;DO 32 x 24 VDC/0.5A

•1 send IM, IM 460-0

You can calculate Current Consumption I in this rack as follows, with the data from the individual data sheets:

Module	Quantity	+5 VDC (Max. Current Consumption
			Values)
		I / Module		I Total
CPU 417-4	1	2600 mA		2600 mA
SM 431; AI 16 x 16 bits	3	700 mA		2100 mA
SM 421;DI 32 x 24 VDC	5	30 mA		150 mA
SM 422;DO 32 x 24 VDC/0.5A	6	200 mA		1200 mA
IM 460-0	1	140 mA		140 mA
Total				6190 mA

From the data in the table, you can see that you must install a power supply module PS 407 10A (for connection to 120/230 VAC) or PS 405 10A (for connection to 24 VDC) in the rack, to cover the current consumption calculated here.

Note

If you wish to connect an ER to the CR via a send IM with current transfer, you must also take the current consumption of this ER into account when choosing the power supply module.

Automation System S7-400	Hardware and Installation	4-3
A5E00850741-01