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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 code	Width × Height
TS35 × 7.5	35 mm W × 7.5 mm H
TS35 × 15	35 mm W × 15 mm H
G-type 15	15 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

Parameter	Leyu spec target	Why 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

Series	Power range	Key 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

Device	Qty	Steady 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

Protection	Trip point	Recovery
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

Wire gauge: AWG 18 (0.82 mm²) for ≤ 5 A; derate one size per 10 °C above 40 °C.
Twist +V and –V conductors to shrink the EMI loop area.
Surge protection: Add Type 2 SPD upstream with high lightning risk (IEC 61643-11).
Negative rail bonding: Bond –V to PE at one point only to avoid ground loops.

Commissioning & Preventive Maintenance

Interval	Task
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

Symptom	Likely cause	Fix
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

Question	Answer
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.