4nic-Casic 4NIC-DC325/G DC/DC Converter – 4NIC Series

4nic-Casic 4NIC-DC325/G: 325 W Galvanically Isolated DC/DC Converter for Industrial Control Architectures

The 4NIC-DC325/G occupies the high-capacity tier of the 4NIC series — a product line developed by 4nic-Casic (a subsidiary of China Aerospace Science and Industry Corporation, CASIC Group) specifically for power conversion duties inside industrial control cabinets. At 325 W rated output, this module is sized to serve as the primary DC bus supply for multi-axis PLC racks, distributed I/O assemblies, and DCS field controller enclosures where load aggregation from CPU cards, communication processors, and analog I/O modules demands a stable, low-ripple DC rail with deterministic hold-up behaviour under transient load steps.

Unlike general-purpose SMPS units adapted for industrial use, the 4NIC-DC325/G is architected from the ground up for cabinet integration: DIN rail or panel-mount mechanical interface, terminal-block wiring, and a protection stack (OVP / OCP / SCP / thermal shutdown) that prevents cascading failures when a downstream module faults. The galvanic isolation barrier between input and output eliminates ground-loop coupling — a persistent source of ADC noise and communication errors in mixed-signal cabinets where 24 VDC control wiring runs adjacent to 230 VAC feed conductors.

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Technical Parameters

Hardware Logical Analysis

The 4NIC-DC325/G employs a full-bridge or phase-shifted full-bridge switching topology — the preferred architecture at the 300 W+ power class because it achieves zero-voltage switching (ZVS) on the primary-side MOSFETs, reducing switching losses and the associated high-frequency EMI signature. This matters in control cabinet environments where radiated emissions from the power supply can couple into adjacent analog input wiring, corrupting 4–20 mA process signals or introducing jitter on RS-485 fieldbus lines.

EMC Design Discipline: The input stage incorporates a common-mode choke and X/Y capacitor network to attenuate conducted emissions back onto the DC bus. This is particularly relevant in installations where multiple converters share a common DC rail from a central rectifier — without adequate input filtering, switching harmonics from one converter can modulate the output of adjacent units. The 4NIC-DC325/G’s input filter is designed to meet CISPR 11 Class A limits, making it compatible with industrial environments without additional external filtering in most installations.

Isolation Barrier Architecture: The transformer isolation stage provides galvanic separation between the input DC bus and the output control rail. The isolation capacitance across the barrier is kept low to minimise high-frequency common-mode current paths — a design discipline that directly reduces ground-loop noise in systems where the control-side 0 V reference is connected to protective earth at a single point. For PLC installations following IEC 61131-2 wiring guidelines, this single-point earthing combined with the 4NIC-DC325/G’s low inter-winding capacitance produces measurable improvement in analog I/O accuracy.

Output Regulation and Hold-Up: The output stage uses synchronous rectification with a post-filter LC network tuned to maintain output ripple below 1% pk-pk across the full load range. The bulk output capacitance is sized to provide adequate hold-up time during brief input interruptions — a critical parameter for PLC systems where a sub-cycle input dropout must not cause a CPU reset or I/O module re-initialisation cycle.

Thermal Management: The power stage components are mounted on an internal heatsink with calculated thermal resistance to maintain junction temperatures within safe limits at 325 W continuous output in a 70 °C ambient. The thermal shutdown threshold is set conservatively below the component derating knee, ensuring the protection circuit activates before any component reaches its absolute maximum rating — a design margin that directly extends service life in high-ambient installations such as outdoor enclosures or foundry environments.

System Integration Benefits

• Single-module 325 W capacity: Eliminates the need for parallel power supply configurations in medium-density PLC racks, reducing wiring complexity, potential single points of failure from load-sharing imbalance, and cabinet footprint.
• Deterministic output stability: Load regulation ≤ ±1% ensures that voltage-sensitive analog I/O modules and precision transmitters receive a stable reference rail, preventing measurement drift caused by supply voltage variation under dynamic load steps.
• Galvanic isolation for signal integrity: The input-to-output isolation barrier eliminates ground-loop currents that would otherwise appear as common-mode noise on 4–20 mA loops, thermocouple inputs, and RTD measurement circuits sharing the same cabinet ground reference.
• Multi-layer protection stack: OVP, OCP, SCP, and thermal shutdown operate independently and in combination, preventing a single fault condition from propagating to connected PLC modules — a requirement in safety-instrumented system (SIS) auxiliary power architectures.
• DIN rail mechanical compatibility: EN 60715 DIN rail mounting with standard terminal block wiring interface allows direct installation into existing cabinet layouts without custom brackets or cable modifications, reducing retrofit engineering hours.
• Low EMI emission profile: CISPR 11 Class A compliant input filtering reduces the risk of interference with co-located fieldbus communications (PROFIBUS, Modbus RTU, DeviceNet) that are sensitive to conducted noise on shared DC distribution rails.
• Wide operating temperature range: -20 °C to +70 °C operating envelope covers outdoor enclosures, unheated plant rooms, and high-ambient process areas without derating or auxiliary cooling, reducing total cost of ownership.
• High MTBF for reduced maintenance burden: >100,000 hours MTBF at 25 °C translates to statistically low failure rates over a 10-year plant lifecycle, supporting predictive maintenance intervals rather than reactive replacement schedules.
• CASIC supply chain traceability: Manufactured within the CASIC Group industrial electronics supply chain, providing batch-level traceability documentation for quality-critical procurement in petrochemical, power generation, and rail transit applications.
• Auto-recovery protection: After an OCP or SCP event clears, the module restores output automatically without manual intervention — reducing operator response time requirements in unmanned remote stations and SCADA-monitored installations.

Quality Assurance & Global Logistics

Every 4NIC-DC325/G unit supplied by siemensplc.com is sourced from authorised 4nic-Casic distribution channels. Units are not refurbished, grey-market, or third-party rebranded. Pre-shipment inspection includes visual examination of housing integrity, label verification against batch documentation, and functional power-on verification where applicable.

Shipments originate from our warehouse in Xiamen, China — a major logistics hub with direct access to international express carriers (DHL, FedEx, UPS) and sea freight consolidators. Typical transit times: 3–7 business days to Southeast Asia and East Asia; 5–10 business days to Europe and the Middle East; 7–14 business days to the Americas and Africa. Express options are available for urgent maintenance and breakdown situations. All shipments include full tracking and commercial invoice documentation for customs clearance. Export packing is ESD-safe and impact-resistant, suitable for air freight handling.

A 12-month warranty covers manufacturing defects from the date of shipment. RMA requests are processed within 2 business days of receipt. Replacement units are dispatched from Xiamen stock, minimising downtime for critical installations.

Contact Information

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