SIEMENS 6ES5931-8MD11 Power Supply PS931 | Replacement, Equivalent & Selection Guide
The SIEMENS 6ES5931-8MD11 is a PS931 Power Supply module designed for the SIMATIC S5 programmable controller series. This page provides full technical specifications, compatible replacement options, equivalent models, and a practical selection guide to help engineers and procurement teams make informed sourcing decisions.
Technical Specifications
- Part Number: 6ES5931-8MD11
- Series: SIMATIC S5 / PS931
- Manufacturer: Siemens AG
- Module Type: Power Supply Unit (PSU)
- Input Voltage: AC 120/230 V (switchable)
- Output Voltage: DC 5 V / 24 V
- Mounting: Rail-mount, compatible with S5-115U / S5-135U / S5-155U racks
- Protection Class: IP20
- Weight: Approx. 400 g
- Operating Temperature: 0 °C to +60 °C
- Standards: CE, UL, IEC 61131-2
Compatible Replacement & Equivalent Models
The following models are commonly evaluated as replacements or equivalents for the 6ES5931-8MD11. Compatibility depends on rack type, output current requirements, and firmware version — always verify before substitution.
- 6ES5931-8MD21 — Updated revision of the same PS931 family; direct form-fit-function replacement in most S5 racks
- 6ES5931-8MC11 — Lower output current variant; suitable for smaller S5 configurations
- 6ES5931-8MB11 — Earlier revision; functionally equivalent but may require firmware check
- 6ES5955-3LC41 — PS955 series alternative for S5-115U; verify rack slot compatibility
- Third-party compatible PSUs — Several industrial PSU manufacturers offer drop-in replacements; contact Konmask for vetted options
Note: Siemens SIMATIC S5 is a legacy platform. Siemens officially recommends migration to the S7-300 or S7-1500 series for new projects.
Why Choose the Original Model
- Guaranteed compatibility with all SIMATIC S5 racks and I/O modules without modification
- Proven field reliability in continuous industrial operation over decades
- Siemens-certified output stability and protection circuits (overvoltage, short-circuit, overtemperature)
- Traceable manufacturing with full documentation for regulated industries (automotive, pharma, utilities)
- Reduced integration risk — no re-validation required when replacing like-for-like
Typical Applications
- Legacy SIMATIC S5 PLC system maintenance and spare parts replenishment
- Automotive assembly line control panels
- Chemical and petrochemical process control systems
- Water treatment and utility SCADA infrastructure
- Food & beverage production line automation
- Building management and HVAC control systems
System Compatibility
- Compatible Racks: SIMATIC S5-115U, S5-135U, S5-155U
- Compatible CPUs: CPU 941, CPU 942, CPU 943, CPU 944, CPU 945, CPU 946/947, CPU 948
- Compatible I/O: All standard S5 digital and analog I/O modules
- Not compatible with: SIMATIC S5-90U, S5-95U (different PSU form factor); S7 series (different platform)
Selection Guide
Use the following criteria to confirm the 6ES5931-8MD11 is the right choice — or to identify the best alternative:
- Step 1 — Identify your rack: Confirm you have an S5-115U, S5-135U, or S5-155U rack. Check the rack label or existing PSU slot dimensions.
- Step 2 — Check output current demand: Sum the current draw of all installed modules. The 6ES5931-8MD11 must meet or exceed total load.
- Step 3 — Verify input voltage: Confirm site supply is AC 120 V or AC 230 V and that the PSU switch is set correctly.
- Step 4 — Check revision compatibility: If replacing an existing PSU, match the revision suffix (-8MD11 vs -8MD21) or confirm cross-revision compatibility with your system integrator.
- Step 5 — Consider migration: For new projects or major retrofits, evaluate migrating to SIMATIC S7-1500 with modern PSUs for long-term support and spare parts availability.
Quality Assurance & Sourcing
- All units sourced through authorized distribution channels or verified surplus with full traceability
- Pre-shipment inspection: visual check, label verification, and functional power-on test where applicable
- Anti-counterfeit measures: hologram labels, serial number verification against Siemens databases
- Packaging: ESD-safe bags, foam-lined cartons, humidity indicators for long-distance shipping
- Warranty: 12-month warranty against manufacturing defects; DOA replacement within 7 business days
How to Order
- Online: Add to cart directly on this page — stock availability shown in real time
- Bulk / Project Inquiry: Email support@konmask.com with quantity, delivery timeline, and destination
- Phone / WhatsApp: +0086 19859288691 — available Mon–Sat, 09:00–18:00 CST
- Lead Time: In-stock orders ship within 1–3 business days; sourced orders typically 7–21 business days
- Export: We ship worldwide with DHL, FedEx, and UPS. Export documentation (CO, packing list, commercial invoice) provided on request.
Replacement & Compatibility FAQ
Q: Can I use the 6ES5931-8MD21 as a direct replacement for the 6ES5931-8MD11?
A: In most cases, yes. The -8MD21 is an updated revision of the same PS931 family and is form-fit-function compatible with the same S5 racks. Verify output current ratings match your system load.
Q: Is the 6ES5931-8MD11 still in production?
A: No. The SIMATIC S5 series has been discontinued by Siemens. Units available are new-old-stock (NOS) or refurbished. Konmask maintains a curated inventory of legacy S5 components.
Q: Can I replace the S5 PS931 with an S7 power supply?
A: No — the S5 and S7 platforms use different PSU form factors and backplane interfaces. A full rack migration is required to move to S7.
Q: What happens if the PSU output current is insufficient for my rack?
A: Insufficient PSU current causes system instability, random CPU faults, or failure to power on. Always calculate total module current draw before selecting a PSU.
Q: Do you provide a test report or certificate of conformity?
A: Yes. A certificate of conformity and inspection report are available upon request for all orders. Contact support@konmask.com.
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