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DIN-Rail Power Supplies — 2025 Industrial Buyer’s Handbook



A step-by-step sizing, selection, and installation guide focused on Leyu Power’s MDR, NDR, and LPV DIN-rail product families. Follow along, and you’ll finish with a spec-checked bill of materials ready for your PLC cabinet. No third-party datasheets or downloads are required.


Why DIN-Rail PSUs Dominate Modern Control Panels


Industrial automation keeps surging: Analysts peg the global DIN-rail PSU market at ≈ US $2.5 billion by 2030, climbing 6 % CAGR on the back of Industry 4.0 retrofits and smart-factory builds. These compact AC/DC bricks snap onto a standard metal rail, feed everything from PLC CPUs to IIoT edge gateways, and—with the right headroom and derating—run ten years or more without a fan.


DIN-Rail Hardware & Standard Dimensions


DIN EN 60715 defines three common “top-hat” rail profiles:

Rail codeWidth × Height
TS35 × 7.535 mm W × 7.5 mm H
TS35 × 1535 mm W × 15 mm H
G-type 1515 mm W × 5.5 mm H


(35 mm rails cover ~95 % of industrial cabinets.) Allow at least a 7.5 mm air gap on each side of the PSU for cooling and clip clearance.


Core Electrical Parameters to Verify


ParameterLeyu spec targetWhy it matters

Input range

88 – 264 VAC

Global mains compatibility

Output tolerance

±1 % V<sub>OUT</sub>

Stable PLC & sensor rails

Ripple/noise

≤ 100 mV<sub>pp</sub> @ 20 MHz

Prevents analog drift

Efficiency

≥ 90 % at full load

Cooler cabinets, lower OpEx

MTBF

≥ 300 k h @ 25 °C

Predictable preventive swap-outs


Leyu Series Cheat-Sheet

SeriesPower rangeKey advantage

MDR

15 – 60 W

Ultra-slim housings for dense I/O stacks

NDR

75 – 480 W

Wide input + active PFC; “-P” models add current-sharing

LPV

35 – 300 W

IP67 epoxy-potted housings for dusty or wet sites


Exact Sizing Workflow (with Worked Example)


The golden rule is to sum all steady currents, convert peak/inrush loads, add a future buffer and temperature derating, and then round up to the next nominal wattage.

Step 1 – Inventory Loads

DeviceQtySteady I (A)Inrush ×Duty %Peak I (A)Weighted I (A)

PLC CPU

1

1.2

1.0

100

1.2

1.2

Servo drive

2

2.0

1.8

40

3.6

2.9

HMI panel

1

0.6

1.0

100

0.6

0.6

Totals

5.4

4.7


Step 2 – Add 20 % Expansion Buffer

Industrial panel guidelines typically reserve 20 % spare capacity for future I/O:

4.7 A × 1.20 ≈ 5.6 A

Step 3 – Apply Temperature Derating

Leyu NDR units run 100 % up to 50 °C, then derate linearly to 50 % at 70 °C. At 55 °C:

I_derated = 5.6 A × [1 − 0.025 × (55 − 50)] ≈ 4.9 A

Select: NDR-120-24 (24 V, 5 A, 120 W). For redundancy, parallel two NDR-120-24-P supplies.


Protection & Safety Checklist


ProtectionTrip pointRecovery

OVP

115 – 140 % VOUT

Latch; power-cycle

OCP

105 – 140 % IOUT

Hiccup auto-reset

OTP

+100 °C internal

Auto-restart after cool-down

Comply with IEC 61010-1 (safety) and EN 55032 Class B (EMC). IEC 60204-1 also recommends documenting spare capacity for risk mitigation.


Mechanical & Thermal Design Rules


  • Mounting orientation: Vertical preferred; horizontal costs ~15 % extra derating.

  • Clearances: ≥ 25 mm above/below for airflow; keep cable ducts from blocking vents.

  • DIN-clip torque: 0.6 N·m max—prevents rail distortion.

  • Conformal coating: Specify in RH > 90 % or salt-fog sites; extends board life.


Wiring & EMC Practices


  1. Wire gauge: AWG 18 (0.82 mm²) for ≤ 5 A; derate one size per 10 °C above 40 °C.

  2. Twist +V and –V conductors to shrink the EMI loop area.

  3. Surge protection: Add Type 2 SPD upstream with high lightning risk (IEC 61643-11).

  4. Negative rail bonding: Bond –V to PE at one point only to avoid ground loops.


Commissioning & Preventive Maintenance


IntervalTask

Startup

Confirm “DC OK” LED steady; adjust trim pot ±1 % of 24 V

18 months

ESR-test electrolytics; replace if > 2× spec

3 years

Infrared scan—flag hotspots > 85 °C

8–10 years

Replace unit during scheduled downtime; recycle per WEEE


Troubleshooting Quick-Guide


SymptomLikely causeFix

LED blinking 2 Hz

OCP engaged

Check load for shorts

Output 0 V, LED off

OTP tripped

Improve airflow, cool the cabinet

27 V output

OVP latched

Cycle AC mains, verify trim


Ready-to-Order Checklist


  • Rail type & length (TS35 × 7.5 or TS35 × 15)

  • Input voltage (single-phase 230 VAC or -phase variant)

  • Output voltage & continuous current + 20 % buffer

  • The highest ambient temperature expected

  • Required safety & EMC marks

  • Planned future I/O expansion

Tick every box, and a Leyu MDR or NDR unit will slap into it.


About Leyu Power


Founded in 2005, Leyu Power manufactures ISO 9001-certified switching PSUs, LED drivers, and inverters for 50+ export regions. They are backed by a 2-year warranty and rapid OEM customization.


Frequently Asked Questions


QuestionAnswer

What safety standards must a DIN-rail PSU meet for industrial panels?

At minimum, IEC 61010-1 for electrical safety and EN 55032 for EMC emissions. If shipping to North America, UL 508 listing is common.

How do I account for temperature when sizing?

Consult the datasheet’s derating curve. Above +50 °C ambient, reduce output current by ~2 % per °C or add forced-air cooling.

Can Leyu DIN-rail PSUs share current in parallel?

Yes. Models with an “-P” suffix include active current-sharing; set their outputs within ±50 mV before paralleling.

What is the typical service life?

Leyu specifies MTBF > 300 000 h at 25 °C, translating to 8–10 years of continuous service if the cabinet stays below 50 °C.

Is field wiring required to be copper only?

IEC 60204-1 recommends copper conductors for control circuits. If aluminium is used, apply antioxidant paste and torque-check annually.




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