Siemens SITOP UPS Modules

Technical Dossier

Product Details And Specifications

Siemens SITOP UPS Series: Comprehensive Module Range and Technical Overview

The Siemens SITOP UPS series represents one of the most widely deployed uninterruptible power supply platforms in global heavy industry. Installed across petrochemical complexes, nuclear power facilities, offshore platforms, and continuous-process refineries, SITOP UPS modules are engineered to bridge power interruptions without process disruption. Their integration with Siemens SIMATIC S7 controllers, PROFINET/PROFIBUS communication infrastructure, and the TIA Portal engineering environment has made them a default specification in plant-wide power continuity architectures. The series spans buffering capacities from seconds-range bridging (capacitor-based) to extended runtime (battery-based), covering 24 VDC load circuits up to 40 A. Installed base density is highest in European and Asian process industries, where IEC 61000 compliance and SIL-rated power continuity are mandatory design criteria.

The Evolution of SITOP UPS Architecture

The SITOP UPS product line has undergone three distinct architectural generations since its introduction in the late 1990s.

Generation 1 (1998–2005): The initial SITOP UPS range introduced standalone 24 VDC buffering using sealed lead-acid (SLA) battery modules. These units operated without fieldbus communication and provided basic DC-OK signaling via relay contact. Representative models include the 6EP1931-2DC21 and early 6EP1931-2EC31 variants. Compatibility was limited to SIMATIC S5 and early S7-300 environments.

Generation 2 (2005–2015): This generation introduced PROFIBUS DP and later PROFINET IO communication interfaces, enabling real-time UPS status monitoring (battery state-of-charge, remaining runtime, fault codes) directly within the SIMATIC engineering environment. The 6EP1931-2FC21 (current product) belongs to this generation. Capacitor-based buffering modules (SITOP CAP) were introduced as maintenance-free alternatives for short-duration bridging requirements. Battery management improvements extended SLA service intervals.

Generation 3 / Current Platform (2015–present): The SITOP UPS1600 and UPS500S sub-families represent the current architecture. These modules feature USB and PROFINET interfaces simultaneously, Windows-compatible UPS software (SITOP UPS Manager), and lithium-ion battery options. Backward compatibility with 24 VDC load buses is maintained, but physical form factors and DIN-rail mounting dimensions differ from Generation 2 units. Plants running Generation 2 hardware face a form-factor migration when upgrading, making like-for-like spare part sourcing the preferred maintenance strategy for installed base continuity.

SITOP UPS Full Catalog & Functionalities (SKU List)

The following SKUs represent the core SITOP UPS module range. Classification follows functional role within the DC power continuity architecture.

Capacitor-Based Buffering Modules (SITOP CAP):

6EP1931-2EC31: 24 VDC capacitor buffer module, 0.5 A load, bridging time up to 100 ms — maintenance-free short-duration bridging for SIMATIC I/O nodes.
6EP1931-2EC41: 24 VDC capacitor buffer, 3 A continuous load, extended capacitor bank — suitable for distributed I/O racks requiring sub-second ride-through.
6EP1931-2EC51: 24 VDC capacitor buffer, 10 A load rating — used for larger I/O clusters and drive control circuits requiring maintenance-free buffering.

Battery-Based UPS Modules (SITOP UPS — Lead-Acid):

6EP1931-2FC21: 24 VDC / 6 A UPS module with PROFINET IO interface, battery-backed, supports runtime monitoring via TIA Portal — primary spare for S7-300/400 power continuity circuits.
6EP1931-2FC31: 24 VDC / 15 A UPS module, PROFINET IO, extended battery capacity — deployed in mid-size control panel applications requiring longer bridging windows.
6EP1931-2FC41: 24 VDC / 20 A UPS module, PROFINET IO, high-current output — used in large SIMATIC ET 200 distributed I/O stations and multi-axis drive systems.
6EP1931-2DC21: 24 VDC / 6 A UPS module, relay-contact DC-OK signal only, no fieldbus — legacy model for non-networked control panels; discontinued, long-tail spare demand active.
6EP1931-2DC31: 24 VDC / 15 A UPS module, relay-contact signaling — legacy high-current variant; replacement typically requires panel rewiring if upgrading to PROFINET-capable successor.

Battery Modules & Accessories:

6EP1935-6MD21: Replacement battery module for SITOP UPS 6 A / 15 A family — sealed lead-acid, 12 V / 7 Ah, direct plug-in replacement, no tools required.
6EP1935-6MD11: Replacement battery module for SITOP UPS 20 A family — 12 V / 12 Ah SLA, extended runtime configuration.
6EP1931-2EC21: SITOP CAP module, 24 VDC, 0.5 A, ultra-compact form factor — used in space-constrained DIN-rail assemblies.

SITOP UPS1600 Series (Current Generation):

6EP4134-3AB00-0AY0: SITOP UPS1600, 24 VDC / 10 A, USB + PROFINET interface, lithium-ion compatible — current-generation replacement for 6 A/15 A legacy UPS modules.
6EP4136-3AB00-0AY0: SITOP UPS1600, 24 VDC / 20 A, USB + PROFINET, lithium-ion compatible — current-generation replacement for 20 A legacy modules.
6EP4137-3AB00-0AY0: SITOP UPS1600, 24 VDC / 40 A, USB + PROFINET — high-current variant for large panel and multi-drive power continuity applications.
6EP4134-3AB00-2AY0: SITOP UPS1600, 24 VDC / 10 A with integrated lithium-ion battery — reduced maintenance interval versus SLA-based predecessors.
6EP1931-2FC11: SITOP UPS module, 24 VDC / 3 A, PROFIBUS DP interface — Generation 2 fieldbus variant for legacy PROFIBUS plant networks; discontinued, spare demand ongoing in brownfield sites.

UPS Software & Communication Accessories:

6EP1961-3BA00: SITOP UPS Manager software license — Windows-based monitoring and configuration tool for UPS1600 series, supports USB and PROFINET connectivity.
6EP1931-2EC11: SITOP CAP module, 24 VDC / 0.5 A, DIN-rail mount — entry-level capacitor buffer for single I/O node protection.

Sourcing Hard-to-Find & Obsolete SITOP UPS Parts

A significant portion of the global SITOP UPS installed base consists of Generation 1 and Generation 2 modules that Siemens has transitioned to limited availability or end-of-life status. Models including the 6EP1931-2DC21, 6EP1931-2DC31, and 6EP1931-2FC11 (PROFIBUS variant) are no longer manufactured but remain in active service across refineries, chemical plants, and power generation facilities operating on 15–25 year maintenance cycles.

DriveKNMS maintains a dedicated inventory program for lifecycle-extended SITOP UPS components. Our sourcing protocol covers:

— New-old-stock (NOS) units sourced from verified industrial surplus channels, with full traceability documentation.
— Reconditioned modules that have undergone full discharge/recharge cycle testing and battery replacement where applicable.
— Battery module cross-referencing for cases where OEM battery part numbers are discontinued but compatible SLA cells remain available.
— Form-factor advisory for plants evaluating whether a like-for-like replacement or a controlled migration to UPS1600 architecture is the lower total-cost option.

For plants under long-term service agreements (LTSA) or operating under change-management-restricted environments (nuclear, pharmaceutical GMP), DriveKNMS can provide multi-year forward stocking arrangements to eliminate emergency procurement risk.

Quality Control for the SITOP UPS Range

SITOP UPS modules present specific verification challenges due to their integrated battery management circuits, capacitor aging characteristics, and fieldbus communication stacks. DriveKNMS applies the following test protocol to all SITOP UPS units prior to dispatch:

1. Input/Output Voltage Verification: 24 VDC input acceptance range (20.4–28.8 VDC) and output regulation under rated load confirmed using calibrated DC electronic load equipment.

2. Battery / Capacitor Health Assessment: For battery-based modules, internal resistance measurement (Hioki BT3554 or equivalent) and full charge/discharge cycle with runtime logging against rated capacity. For capacitor modules, capacitance measurement and leakage current verification per IEC 62391.

3. DC-OK Signal and Relay Contact Test: Threshold voltage for DC-OK relay activation verified against datasheet specification (typically 18–20 VDC dropout). Contact resistance measured at rated switching current.

4. PROFINET / PROFIBUS Communication Stack Verification: For networked variants (6EP1931-2FC21, 6EP1931-2FC31, 6EP1931-2FC41, 6EP1931-2FC11), PROFINET IO device identity, GSDML file compatibility, and cyclic data exchange are verified using a Siemens S7-1500 test rack running TIA Portal V17.

5. Thermal Stress Test: Units operated at 100% rated load for 2 hours at 40°C ambient to verify thermal management and confirm no derating or protection trip occurs.

6. Firmware Version Logging: Firmware version recorded and disclosed to customer prior to shipment. Downgrade/upgrade advisory provided where known compatibility issues exist with specific TIA Portal versions.

All test results are documented and available upon request. Units failing any parameter are quarantined and not offered for sale.