6ES5955-3LF42 - SIMATIC S5 PS955 power supply 40 A

SIMATIC S5 PS955 power supply 40 A that supplies the rack 5 V, 15 V and 24 V rails from AC input.

Documented system function

Rebuilt from individual evidence

System position

Documented characteristics

The source identifies this exact reference as a SIMATIC S5 955 power supply module for S5-135U/-155U central controllers and EU 185U.

In the documented system, supplies the rack 5 V, 15 V and 24 V rails from AC input.

The source documents 5.1 V DC/40 A, 24 V DC/2.8 A, and 15 V DC/2 A outputs.

Inferred system position: between the AC source and the S5-135U/155U rack supply rails.

Exact reference: 6ES5955-3LF42
Category: PLC / CPU
Evidence checked: 2026-09-12

System role

This section explains what the product does and where it acts in the surrounding system.

Function: supplies the rack 5 V, 15 V and 24 V rails from AC input.
System position: Sits between the AC source and the S5-135U/155U rack supply rails.
Upstream / inputs: The AC installation provides the upstream power input.
Downstream / outputs: The PS955 provides the downstream DC rails used by S5 modules.
Limitations: Unknown: the installed system configuration, wiring, firmware state, physical condition and replacement compatibility.

Evidence ledger

Facts, inferences, and unknowns are kept separate.

Facts

The cited source identifies 6ES5955-3LF42 as a SIMATIC S5 955 power supply module for S5-135U/-155U central controllers and EU 185U.
Confidence: high
- cache.industry.siemens.com — retrieved 2026-09-12; high confidence
- www.classicautomation.com — retrieved 2026-09-12; high confidence
The cited source describes 6ES5955-3LF42 as supplies the rack 5 V, 15 V and 24 V rails from AC input.
Confidence: high
- cache.industry.siemens.com — retrieved 2026-09-12; high confidence
- www.classicautomation.com — retrieved 2026-09-12; high confidence
The cited source documents 5.1 V DC/40 A, 24 V DC/2.8 A, and 15 V DC/2 A outputs.
Confidence: high
- cache.industry.siemens.com — retrieved 2026-09-12; high confidence
- www.classicautomation.com — retrieved 2026-09-12; high confidence

Inferences

Inferred system position: between the AC source and the S5-135U/155U rack supply rails.
Confidence: medium
Rationale: The exact-reference identity and documented function establish where this component participates in the described control path.
- cache.industry.siemens.com — retrieved 2026-09-12; high confidence
- www.classicautomation.com — retrieved 2026-09-12; high confidence

Unknowns

Unknown: the installed system configuration, wiring, firmware state, physical condition and replacement compatibility.
Confidence: low
Missing evidence: The individual web sources describe the product but do not establish a particular installation or unit condition.

System position diagram

The upstream system stage connects through the exact product to the downstream system stage. — The exact product participates in the system path described by the cited evidence.

View Mermaid source

flowchart LR; Upstream --> Component; Component --> Downstream

View diagram labels

Nodes: Upstream system stage; Exact product; Downstream system stage
Edges: Documented input or supply path; Documented output or control path

Next action

The captured evidence supports the documented identity and system role of 6ES5955-3LF42.

Unknown: confirm the installed rack, wiring, firmware, unit condition and replacement compatibility before use.

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