Siemens 6EP1933-2EC41 DC UPS Module – SITOP UPS500S

Siemens 6EP1933-2EC41 SITOP UPS500S — 24 V DC Buffer Module for Uninterrupted Industrial Control Power

The Siemens 6EP1933-2EC41 is a 24 V DC uninterruptible power supply buffer module belonging to the SITOP UPS500S product family. It is designed to bridge mains power interruptions in industrial control environments, maintaining a stable 24 V DC rail for connected PLCs, HMIs, field I/O, and safety relays without any output voltage dip or transient. The module operates in conjunction with a compatible SITOP power supply unit and an external battery module, forming a three-component DC UPS architecture that is fully integrated into the SIMATIC automation ecosystem.

Unlike AC UPS systems that introduce inverter-based conversion losses and transfer-time gaps, the 6EP1933-2EC41 operates entirely in the DC domain. The buffer module continuously monitors the input DC bus; upon detecting a voltage drop below the defined threshold, it switches to battery-backed output within microseconds — a transition that is transparent to the connected load. This characteristic makes it particularly suited to applications where even a 20 ms power interruption would trigger a PLC watchdog fault or corrupt an active write cycle in non-volatile memory.

The module communicates with a host system via a USB interface compatible with the SITOP UPS Manager software. This software layer enables real-time monitoring of battery state-of-charge (SoC), estimated runtime under current load, charge cycle count, and battery health status. It also supports configurable shutdown signaling — the UPS Manager can issue an orderly OS shutdown command to an IPC or SCADA workstation before battery depletion, preventing file system corruption in data-intensive applications.

From a cabinet integration standpoint, the 6EP1933-2EC41 mounts on a standard 35 mm DIN rail and occupies a width of 80 mm, making it compatible with the physical footprint of the SITOP PSU8200 and PSU6200 families. The module’s IP20 enclosure rating is consistent with standard control cabinet environments. Operating temperature range of 0 °C to +40 °C covers the majority of industrial indoor installations, while the sealed lead-acid battery chemistry eliminates electrolyte maintenance requirements over the service life of the unit.

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Technical Parameters

Hardware Logical Analysis

The 6EP1933-2EC41 implements a bidirectional DC-DC converter topology at its core. During normal mains-powered operation, the converter operates in charge mode: it draws current from the 24 V DC bus supplied by the paired SITOP PSU and applies a temperature-compensated constant-current / constant-voltage (CC/CV) charge profile to the VRLA battery. The charge current is regulated to prevent thermal runaway in the sealed cell stack, a critical consideration given that VRLA batteries are sensitive to overcharge-induced gassing.

When the input bus voltage falls below the undervoltage detection threshold — typically set at approximately 20.4 V DC (85 % of nominal) — the converter transitions to discharge mode within a sub-millisecond switching interval. In discharge mode, the bidirectional converter boosts the battery terminal voltage (which declines from approximately 27.6 V fully charged to roughly 21 V at end-of-discharge for a 24 V VRLA stack) back to a regulated 24 V DC output. This boost regulation ensures that the output voltage presented to the load remains within the ±1 % tolerance band throughout the discharge curve, preventing any load-side voltage-sensitive device from detecting the transition.

The module’s EMC design addresses conducted and radiated emissions through input filtering with X-capacitors and common-mode chokes on both the DC input and battery terminals. The switching frequency of the internal converter is selected to place fundamental harmonics above the 150 kHz lower boundary of CISPR 11 Class A conducted emission limits, simplifying compliance. Differential-mode filtering suppresses switching ripple on the output bus to levels below 50 mV peak-to-peak under full load — a figure that is within the noise immunity specification of SIMATIC S7-series analog input modules.

The battery management logic embedded in the module tracks cumulative charge throughput (Ah) and applies a periodic equalization charge cycle to balance cell voltages within the VRLA stack. This mechanism extends calendar life by mitigating sulfation on undercharged cells. The USB interface exposes battery SoC, cycle count, and internal resistance measurements to the SITOP UPS Manager, enabling predictive maintenance scheduling before capacity degradation reaches a level that would compromise the required bridging time.

Thermal management is passive: the module relies on convection cooling through ventilation slots in the housing. The internal power dissipation during charge mode is dominated by the converter’s switching losses and the battery’s internal resistance heating. At 40 °C ambient, the module’s thermal design maintains junction temperatures of internal semiconductors within their rated operating envelope without forced airflow, provided that the cabinet’s natural convection path is unobstructed.

System Integration Benefits

• Zero-transfer-time DC switching: The sub-millisecond changeover from mains to battery is transparent to SIMATIC PLCs, eliminating watchdog resets and program cycle interruptions that would occur with AC UPS systems having 4–10 ms transfer gaps.
• Regulated output across full discharge curve: The boost converter maintains 24 V DC ±1 % from 100 % SoC to end-of-discharge, ensuring analog I/O modules and 24 V sensors receive a stable supply throughout the bridging interval.
• Deterministic shutdown sequencing via UPS Manager: Configurable runtime thresholds allow the software to trigger an orderly SCADA or IPC shutdown before battery exhaustion, preserving data integrity in historian and recipe management systems.
• Native SITOP ecosystem compatibility: Direct mechanical and electrical pairing with SITOP PSU8200 (6EP1334-3BA10) and PSU6200 (6EP1334-2BA20) eliminates inter-vendor integration complexity and ensures coordinated diagnostic reporting within TIA Portal.
• Real-time battery health telemetry: USB-connected SoC, internal resistance, and cycle count data enable condition-based maintenance scheduling, replacing fixed-interval battery replacement with evidence-based decisions.
• Compact DIN rail footprint: The 80 mm width allows the UPS module to be added to existing control panels without cabinet redesign, reducing retrofit project scope and cost.
• Maintenance-free VRLA chemistry: Sealed construction eliminates electrolyte topping, venting requirements, and the associated safety classifications that apply to flooded lead-acid installations in enclosed cabinets.
• EMC-hardened output bus: Output ripple below 50 mV peak-to-peak under full load prevents interference with 4–20 mA analog loops and high-resolution encoder feedback signals sharing the 24 V DC distribution rail.
• Temperature-compensated charging: The CC/CV charge algorithm adjusts voltage setpoints based on ambient temperature, preventing undercharge at low temperatures and overcharge-induced gassing at elevated temperatures — both of which accelerate VRLA capacity loss.
• Scalable bridging time: Bridging duration is determined by the capacity of the connected external battery module, allowing system designers to specify runtime from seconds to tens of minutes without changing the buffer module itself.

Quality Assurance & Global Logistics

Every Siemens 6EP1933-2EC41 unit supplied by siemensplc.com is sourced as genuine Siemens factory-manufactured product. Units are procured through verified supply channels with full batch traceability. Prior to dispatch, each module undergoes physical inspection covering label authenticity, housing integrity, serial number format verification against Siemens MLFB conventions, and holographic marking examination. Functional bench testing confirms correct power-up behavior and USB communication response before packaging.

Shipments originate from our warehouse in Xiamen, China — a major export hub with direct access to international express freight networks. Standard export documentation is provided with every shipment: commercial invoice, packing list, certificate of origin, and customs declaration. For time-critical requirements, DHL Express and FedEx International Priority services typically deliver to major industrial centers in Europe, Southeast Asia, the Middle East, and North America within 3–5 business days. Sea freight consolidation is available for bulk orders where lead time permits. All units are packed in anti-static, shock-resistant packaging appropriate for sensitive electronic modules.

A 12-month warranty against manufacturing defects applies to all genuine new units. Dead-on-arrival claims are processed within 7 days of receipt notification. Volume pricing is available for orders of 5 or more units; contact us with quantity and delivery requirements for a formal quotation.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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