Siemens / SIMATIC S7-400

Racks, power supplies, SM 421, SM 422, SM 431, SM 432 and interface modules. The big rack platform.

The S7-400 is the high end SIMATIC rack, used where the plant is large, the availability requirement is high, or both. Discontinued, and still running in New Zealand power generation, pulp and paper and large process plant.

Lower volume than the S7-300 but much higher value per part, and there are fewer people who can supply it.

Racks

The digit that tells you the rail material

In 6ES7400-1TAx1-0AA0, the x is the rail material. 0 is sheet steel, 1 is aluminium. Everything else is identical and the aluminium version is about a kilo lighter. Nobody publishes this, and it decides whether what arrives matches what came out.

Power supplies

PS 407 runs on AC. PS 405 runs on DC. That one sentence prevents most wrong orders on this platform.

Backup battery: 6ES7971-0BA00. Lithium AA, 3.6 V, 2.3 Ah. Siemens rates the shelf life at ten years and notes the lithium content is under 0.5 g, so no special transport measures are required. That differs from the S7-300 battery advice and people often assume the restriction applies.

Power supplies go in slots 1 to 4 only

They must fill from slot 1 with no gaps. Siemens warns a supply inserted in a wrong slot may be damaged and will simply not power up.

Recovery is documented. Disconnect from the mains, not just the standby switch. Remove the module. Fit it in slot 1. Wait at least one minute. Switch on again.

Redundant supplies

Two PS 407 10A R or PS 405 10A R give a redundant supply. Three things worth knowing: in redundant operation the total draw across all modules is still limited to 10 A, either module can be exchanged while the system runs, and true redundant battery backup needs two batteries in each module rather than one in each.

With two supplies fitted but only one switched on, expect a power-up delay of up to one minute.

SM 421 digital input

Only the 7BH01 and 7DH00 support parameter assignment and channel diagnostics. The 7BH01 also supports a redundant sensor supply, which matters on high availability plant.

SM 422 digital output

SM 431 analog input

The 1KF10 and 1KF20 are both AI 8 x 14 bit and are not the same module. The 1KF20 has different interference frequency suppression and filter settling behaviour. Check which one the configuration expects.

SM 432 analog output

Interface modules, ordered as matched pairs

The IM 463-2 deserves a mention. It lets an S7-400 drive existing SIMATIC S5 expansion units. For a plant that has half migrated off S5, it is the bridge, and there is essentially no alternative.

ER1 and ER2 expansion racks have real restrictions

Siemens is explicit about this and it catches people out.

• Interrupts from modules in an ER rack have no effect, because there are no interrupt lines
• Modules are not supplied with 24 V, so anything needing a 24 V supply cannot be used there
• Modules are not battery backed, from either the supply battery or the external CPU supply
• Battery monitoring on a supply fitted in an ER rack should always be switched off

If you have fitted a diagnostic module into an ER rack and interrupts never arrive, that is why.

Ancillaries

CPUs

This is a partial list. If your CPU is not here, send the number and we will identify and quote it.

Engineering software matters on this platform. The 412-1 and 412-2 require STEP 7 V5.4 or higher with HSP 261. The 412-2 PN requires STEP 7 V5.5 or higher with HSP 262. Check your engineering station can configure the CPU before you buy it.

Send us your article numbers

Rack, supply, CPU or modules. Tell us the rack type and how many racks you are running, because it changes which interface modules you need. Quotes in NZD including GST.

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Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Siemens AG. All trademarks, brand names and article numbers are the property of their respective owners and are used here for identification purposes only.