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IEC TS 62735-1-2015: DC Plugs and Socket-Outlets for ICT Equipment (2,6 kW)
2.6 kW DC Power Connector System for Data Centres and Telecom Central Offices
1. Introduction and Scope
IEC TS 62735-1-2015, prepared by SC 23B (Plugs, socket-outlets and switches) of IEC TC 23, specifies a DC plug and socket-outlet system rated at 2.6 kW for information and communication technology (ICT) equipment installed in data centres and telecom central offices. This Technical Specification addresses the growing demand for efficient DC power distribution in facilities that traditionally rely on AC distribution with multiple power conversion stages. By enabling direct DC distribution at voltages from 294 V to 400 V, this standard helps eliminate unnecessary AC-DC and DC-AC conversion losses, improving overall facility energy efficiency by 5-15%.
Tip: The standard covers both rewirable and non-rewirable (moulded-on) plug configurations, as well as fixed socket-outlets, cord extension sets, and multiple socket-outlets (power distribution units/PDUs) for rack mounting. This provides a complete ecosystem for DC power distribution in data centres.
2. Ratings, Classification, and Construction
2.1 Electrical Ratings
| Parameter | Value | Notes |
|---|---|---|
| Rated Power | 2.6 kW | At any voltage within range |
| Rated Voltage Range | 294 V to 400 V DC | Covers common DC bus voltages in telecom/data centre applications |
| Rated Current (calculated) | 6.5 A at 400 V, 8.8 A at 294 V | P = V x I |
| Ambient Temperature Range | -5 °C to +40 °C | 24h average not exceeding 35 °C |
| Pollution Degree | 2 (as per IEC 60664-1) | Non-conductive pollution with temporary condensation |
2.2 Classification
Accessories are classified by connection method (rewirable/non-rewirable), terminal type (screw-type or screwless for rigid and/or flexible conductors), and degree of protection against electric shock. The standard requires shutters on socket-outlets to protect against accidental contact with live parts when the plug is withdrawn — a critical safety feature for DC systems where arcing is more persistent than in AC.
Warning: DC arcs do not have natural zero-crossings like AC arcs, making them much harder to extinguish. The standard addresses this through specific requirements for contact design, material selection (silver-alloy contacts are recommended), and the duration of test currents during short-circuit testing. Never use AC-rated connectors in DC applications without proper DC rating verification.
3. Type Testing and Safety Requirements
3.1 Key Test Categories
The standard defines a comprehensive suite of type tests and routine tests. The type tests include:
- Mechanical tests: Insertion/withdrawal forces (min 5 N, max 50 N), mechanical endurance (5000 cycles), cord anchorage pull/push/torque testing
- Electrical tests: Voltage withstand (dielectric test at 2.5 kV DC), insulation resistance (>5 MΩ), temperature rise test at rated current
- Thermal tests: Glow-wire test (IEC 60695-2-11) for resistance to abnormal heat, ball pressure test for insulating materials
- Environmental tests: Resistance to heat, fire, and tracking (CTI ≥ 175 V for insulating parts)
- Short-circuit test: The complete plug/socket-outlet system must withstand prospective short-circuit currents without creating a fire or electric shock hazard
3.2 Critical Safety Tests for DC Systems
| Test | Requirement | Why It Matters for DC |
|---|---|---|
| Temperature rise | ≤45 K above ambient | DC arcs generate sustained heat; connector temperature must be controlled |
| Short-circuit withstand | No fire, no exposure of live parts | DC arc persistence increases fire risk |
| Mechanical endurance | 5000 cycles without damage | Data centre equipment is frequently swapped |
| Glow-wire test (650 °C) | No ignition of insulating parts | Fire safety in high-density equipment environments |
| Shutter operation | Automatic closure, withstand 5 N probe | Prevents accidental contact under DC voltage |
Engineering Insight: For data centre power distribution unit (PDU) designers, IEC TS 62735-1 offers a standardized DC connector system that eliminates the need for custom DC connectors. The 2.6 kW rating is well-matched to typical server power consumption. Using a single standardized DC connector throughout the facility enables hot-swappable power distribution and reduces training requirements for maintenance personnel. Consider implementing a colour-coding scheme (e.g., grey/blue connectors for DC vs. black for AC) to prevent accidental cross-connection.
4. Application Guidance for Data Centres
When deploying 380 V DC power distribution using IEC 62735-1 connectors, several practical considerations apply:
- Cable sizing: Use appropriately rated DC cables (typically 2.5-4 mm² for 2.6 kW circuits). Cable length should account for voltage drop — for 380 V DC distribution within a rack row, 10-20 m is typical.
- Polarity marking: DC connectors must be clearly marked for polarity (+ and -) to prevent reverse-connection damage to ICT equipment.
- RCD/GFCI protection: DC residual current detection is different from AC; ensure residual current devices are rated for DC operation.
- Connector intermateability: Only connectors conforming to the same standard should be mated. Mixing with connectors from other standards (e.g., IEC 60320 or IEC 60309) is prohibited.
Critical: The standard’s ambient temperature rating of 40 °C with 24h average not exceeding 35 °C is often challenged in high-density data centres where rack inlet temperatures may reach 45-50 °C. In such environments, derating of the connector’s current-carrying capacity may be necessary. Consult the manufacturer’s derating curves and consider active cooling of the power distribution infrastructure.
5. Frequently Asked Questions
Q1: Can IEC 62735-1 connectors be used for AC applications?
A: No. The standard is specifically designed for DC applications only. The connector dimensions, contact design, and clearances are optimized for DC voltage (294-400 V). Using these connectors for AC mains would not comply with AC-specific standards and could create safety risks.
Q2: What is the difference between TS 62735-1 and TS 62735-2?
A: Part 1 specifies the connector system for 2.6 kW. Part 2 (not yet published at the time of this writing) addresses higher-power DC connector systems for ICT equipment, covering ratings beyond 2.6 kW for larger equipment and future power demands.
Q3: Are these connectors compatible with existing 48 V DC telecom systems?
A: No. The 294-400 V DC range of IEC 62735-1 is incompatible with traditional -48 V DC telecom systems. The higher voltage is used for efficient power distribution to modern ICT equipment. Legacy 48 V systems require different connectors (e.g., Anderson Powerpole or similar, covered by other standards).
Q4: How many insertion/withdrawal cycles are these connectors rated for?
A: The standard specifies 5000 cycles of mechanical endurance testing. In practice, quality connectors can achieve 5000-10000 cycles with proper maintenance. For frequently swapped equipment (e.g., test benches), consider using connectors rated for higher cycle counts or using sacrificial patch cords.
