Siemens 6EP1331-1SH02 Industrial Power Supply – SITOP Smart

Siemens 6EP1331-1SH02 SITOP Smart 24VDC/2A — Regulated DIN Rail Power Supply for Industrial Control Systems

The Siemens 6EP1331-1SH02 is a single-phase regulated switched-mode power supply from the SITOP smart product family, engineered for continuous-duty operation in industrial control cabinets. It converts 1-phase AC mains (85–264 V AC, 47–63 Hz universal input range) to a stabilized 24 V DC output at a rated current of 2 A (48 W). The unit mounts directly on a 35 mm DIN rail (EN 60715) and occupies a 45 mm wide footprint, making it a compact yet capable primary power source for SIMATIC S7 PLCs, distributed I/O stations, SIRIUS motor starters, and field instrumentation loops.

Within a control loop, the 6EP1331-1SH02 occupies the role of the primary energy conversion node. Its output rail feeds the 24 V DC bus that supplies CPU logic, I/O backplane power, and sensor/actuator circuits simultaneously. Voltage regulation accuracy is held within ±1% under static load conditions, and the output ripple is suppressed to ≤150 mV peak-to-peak — both figures critical for maintaining the noise immunity margins required by SIMATIC S7-300/400 backplane specifications. The power supply’s active power factor correction (PFC) stage draws near-sinusoidal current from the mains, reducing harmonic distortion and protecting upstream transformer capacity in facilities with dense automation infrastructure.

The SITOP smart series was designed as a cost-optimised complement to the SITOP modular and SITOP PSU8200 families, sharing the same output voltage accuracy and diagnostic signalling philosophy while targeting applications where redundancy modules or parallel operation are not primary requirements. The 6EP1331-1SH02 therefore represents the entry point into Siemens’ structured power supply ecosystem, fully compatible with SITOP UPS modules (e.g., 6EP1931-2DC42) for battery-backed ride-through, and with SITOP selectivity modules for downstream short-circuit selectivity without tripping the main supply.

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Technical Parameters

Hardware Logical Analysis

The 6EP1331-1SH02 is built around a flyback converter topology operating at a fixed switching frequency in the 60–100 kHz range. This topology was selected by Siemens engineers for the SITOP smart class because it provides galvanic isolation between the AC input and DC output with a single magnetic component, minimising BOM complexity while meeting the reinforced insulation requirements of EN 60950-1 / IEC 62368-1 for industrial control equipment.

EMC Design Architecture: The input filter stage incorporates a two-stage common-mode choke combined with X- and Y-class capacitors, attenuating conducted emissions to comply with EN 55011 Class B limits — the more stringent residential-grade classification, which provides margin when the unit is deployed in mixed-use facilities. The transformer’s primary-to-secondary screen winding diverts displacement currents away from the output rail, reducing high-frequency noise coupling that would otherwise manifest as ground-loop interference in analogue sensor circuits connected to the same 24 V bus.

Output Regulation Loop: Secondary-side regulation is implemented via an optocoupler-isolated feedback path using a TL431 precision shunt reference. This architecture eliminates the need for an auxiliary winding on the primary side for regulation sensing, improving cross-regulation performance when the output load transitions rapidly — a condition common in PLC systems where multiple I/O modules switch simultaneously during scan-cycle updates.

Short-circuit and Overload Behaviour: The protection circuit operates in hiccup mode: upon detecting an output short, the controller halts switching, waits a defined off-time (typically 200–500 ms), then attempts restart. This cycle repeats until the fault clears, limiting average power dissipation in the transformer and output rectifier to safe levels without requiring a manual reset. The DC OK contact opens within 2 ms of the output voltage falling below approximately 90% of nominal, providing a hardware-level fault signal that can be wired directly into a SIMATIC CPU digital input for PLC-level diagnostics without any additional signal conditioning.

Thermal Management: The unit uses a natural convection cooling strategy with a vertically oriented PCB and a low-profile aluminium heatsink bonded to the primary-side switching transistor. At 45 °C ambient, the unit delivers full 2 A output; above this threshold, a linear derating curve applies, reaching approximately 1.6 A at 60 °C. This derating characteristic is documented in the SITOP smart operating instructions (A5E00452865) and must be factored into cabinet thermal calculations for installations in tropical climates or sealed enclosures.

System Integration Benefits

• Universal AC Input Eliminates Voltage Selection: The 85–264 V AC wide-range input accepts both 120 V (North American) and 230 V (European/Asian) mains without jumper reconfiguration, reducing procurement complexity for OEMs shipping identical machine variants to multiple markets.
• DC OK Contact Enables PLC-Level Power Diagnostics: The floating relay output wires directly to a SIMATIC S7 digital input channel. Engineers can implement power-fail detection logic in the PLC program without external relays or signal converters, reducing panel wiring labour and improving diagnostic transparency in SCADA/HMI systems.
• SITOP Ecosystem Compatibility: The 24 V output bus is electrically compatible with SITOP UPS1600 (6EP1931-2DC42) and SITOP UPS500S buffer modules, enabling seamless addition of battery-backed ride-through for controlled PLC shutdown sequences without replacing the primary supply.
• Selectivity Module Support: Downstream SITOP selectivity modules (e.g., 6EP1961-2BA00) can be added to the output bus to provide independent short-circuit protection for individual load branches, preventing a fault on one branch from collapsing the entire 24 V rail — a critical requirement in safety-instrumented systems where multiple independent loops share a common supply.
• Deterministic Hold-up Time for PLC Scan Integrity: The ≥20 ms hold-up time at full load covers the worst-case mains half-cycle dropout duration specified in EN 61000-4-11 (Voltage Dips and Interruptions), ensuring the SIMATIC CPU completes its current scan cycle and executes a controlled stop rather than experiencing an uncontrolled power loss that could corrupt retentive data memory.
• Low Output Ripple Protects Analogue I/O Accuracy: The ≤150 mV peak-to-peak ripple specification is well within the noise rejection capability of SIMATIC SM 331 analogue input modules (which specify a common-mode rejection ratio of ≥80 dB at 50/60 Hz), preserving measurement accuracy in 4–20 mA process loops without requiring additional output filtering capacitors.
• Compact 45 mm Width Maximises DIN Rail Density: In a standard 600 mm wide control cabinet with a 400 mm DIN rail, the 45 mm footprint allows up to eight 6EP1331-1SH02 units per rail row, supporting multi-zone machine architectures where each zone requires an independent 24 V supply for fault isolation.
• ATEX Zone 2 Certification Extends Deployment Scope: The ATEX II 3G certification permits installation in Zone 2 hazardous areas (locations where explosive gas atmospheres are not likely to occur in normal operation but may occur in abnormal conditions), broadening the unit’s applicability to oil & gas, chemical processing, and pharmaceutical manufacturing environments without requiring an additional certified enclosure for the power supply itself.
• SEMI F47 Compliance for Semiconductor Fab Compatibility: Compliance with SEMI F47-0706 (Specification for Semiconductor Processing Equipment Voltage Sag Immunity) confirms the unit sustains operation through voltage sags to 50% of nominal for up to 200 ms, meeting the power quality requirements of semiconductor fabrication tool builders.

Quality Assurance & Global Logistics

Every 6EP1331-1SH02 unit supplied by siemensplc.com is sourced directly from Siemens AG authorised distribution channels or verified surplus stock with full traceability documentation. Each unit undergoes a four-stage incoming inspection protocol before dispatch: (1) visual inspection of housing, label, and date code against Siemens factory markings; (2) functional power-on test verifying output voltage within ±0.5% of 24.0 V DC under a 50% resistive load; (3) DC OK contact continuity verification; and (4) packaging integrity check with anti-static and moisture-barrier protection for international transit.

Shipments originate from our warehouse in Xiamen, Fujian Province, China — a major logistics hub with direct access to Xiamen Gaoqi International Airport (XMN) and Xiamen Port, one of China’s top-five container ports by throughput. Standard international express delivery (DHL / FedEx / UPS) achieves transit times of 3–5 business days to most destinations in Southeast Asia, the Middle East, and Europe, and 5–7 business days to North and South America. For urgent requirements, same-day dispatch is available for orders confirmed before 14:00 CST. All shipments include a commercial invoice, packing list, and certificate of origin. Customs HS code 8504.40 applies to this product category.

A 12-month warranty covers manufacturing defects under normal operating conditions as defined in Siemens operating instructions document A5E00452865. Warranty claims are processed with a target replacement or repair turnaround of 10 business days from receipt of the returned unit at our Xiamen facility.

Contact Information

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