TDK-Lambda DSP30-24 DIN Rail Mount Switching Power Supply

DSP DIN rail AC-DC power supply, DSP30-24, rated output 24VDC / 30W class, DIN35 rail mounting, Class II double insulation, no protective earth terminal required

1. Core Electrical Specifications

Input

AC: 90~264VAC, 47~63Hz (wide input voltage for global use)

DC input compatible: 120~370VDC

Built-in PFC, compliant with EN61000-3-2

Cold-start inrush current: 25A@115VAC /50A@230VAC

Output

Rated voltage: 24VDC, adjustable range 24~28VDC via potentiometer

Rated current: 1.3A, rated power 31.2W

Voltage regulation accuracy: ±1%; ripple & noise: 50mV (20MHz bandwidth)

Protection functions: Overcurrent protection (110~160%, fold-back current limiting, short-circuit protection), overvoltage protection 30~36Vdc, overtemperature protection

Hold-up time: 25ms @115VAC input

Efficiency: Typical 83%~87%

2. Mechanical & Environmental

Mounting: Standard 35mm DIN rail

Dimensions: W53mm × H95.5mm × D55.6mm

Weight: Approx. 200g

Cooling: Natural convection, fanless

Operating temperature: -25℃ ~ +71℃; derating starts above 61℃ (2.5%/℃)

Storage temperature: -25~+85℃; humidity 20~90%RH (non-condensing)

3. Indicator LEDs & Terminal Definition

L: AC Line; N: AC Neutral

+: 24V Output Positive; −: Output Negative

Vout ADJ: Output voltage trim potentiometer

Green LED: DC OK (Output normal)

Red LED: DC LO (Undervoltage / Fault)

4. Certifications & Safety

Safety standards: EN60950-1, UL60950-1, UL1310 Class2 output, CE/UKCA

EMC: EN55032 Class A; Immunity to EN61000-4 series

Isolation withstand voltage: 3kV AC

5. Model Status & Replacements

DSP30-24 legacy model: NRND (Not Recommended for New Design); upgraded model DSP30-24/277A2, supports wider input 90~304VAC, direct rail replacement, verify pin definition before use

6. Typical Applications

PLC, sensors, solenoid valves, small control cabinets, building automation, 24V industrial low-voltage power supply, ideal for compact cabinet installation.

7. Common Troubleshooting
8. Green LED off: Check AC input L/N, internal fuse, and minimum input voltage
9. Red LED steady on: Output overload or short circuit; disconnect load to test power supply recovery
10. Output voltage too high/low: Adjust Vout ADJ potentiometer
11. Voltage drop under high temperature: Exceed derating temperature; reduce load or improve cabinet ventilation
12. Domestic Compatible Alternatives

Meanwell: DR-30-24 (30W, DIN rail)

Delta: DRP-24V30W

Mornsun: LI30-24B24

DSP30-24 (DSP30-24VDC) Application Cases

Core advantages: Slim depth (only 56mm), Class II double insulation without PE, fanless natural cooling, wide input voltage, well suited for wall-mounted small electrical boxes and slim control cabinets; rated 24V 1.3A, recommended total load power ≤25W for derating margin

Case 1: Building Management System (BMS) / HVAC Control (OEM Primary Application)

Loads: Small DDC controllers, temperature & humidity transmitters, differential pressure sensors, electric damper actuators, room panels

System Description: Slim wall-mounted low-voltage cabinet, DSP30-24 DIN-rail mounted locally to supply HVAC field I/O modules and sensors. Class II design eliminates PE wiring and simplifies cabling.

Selection Notes: Total current of multiple sensors + small dampers ＜1A; full power available if cabinet temperature ≤61℃.

Typical Sites: Office buildings, shopping malls, hospital air handling units, fresh air unit local control cabinets.

Case 2: Access Control & Security / Fire Alarm Systems

Loads: Access controller, door contacts, card readers, fire alarm input modules, sounder beacons, zone modules

System Description: Wall-mounted security/fire control cabinet, AC220V feeds DSP30-24, 24VDC output powers access host and alarm modules. Wide 90~264VAC input provides tolerance against grid voltage fluctuation. Built-in short/overcurrent protection prevents host damage from field wiring short-circuit.

Note: Not for fire main backup power loops, used for auxiliary monitoring and access control subsystems only.

Case 3: Small Industrial Automation Cabinets (Standalone Stations)

Loads: Micro PLC (Siemens S7-200SMART, Mitsubishi FX3U compact CPU), proximity sensors, photoelectric sensors, relay modules, small solenoid valves

System Description: Local control cabinet for assembly line stations, inspection benches, small conveyors. One PLC + 4~8 sensors + 2~3 small solenoid valves.

Caution: Solenoid valves draw high inrush current, reserve margin for surge current during load calculation; recommended total steady-state load ≤25W.

Suitable for: Sorting stations, inspection equipment, small packaging machine local controls.

Case 4: Remote Monitoring & IoT Data Acquisition Cabinets

Loads: RTU, data acquisition modules, 4G/5G gateways, pressure/level transmitters, wireless sensors

System Description: Remote acquisition cabinets for water, heat, oil & gas sites or equipment rooms. Wide input range and -25℃ cold-start capability for non-constant-temperature environments.

Features: Fanless natural convection, no wearing parts, maintenance-free for unattended sites.

Case 5: Small Intelligent Lighting Control Systems

Loads: DALI lighting gateway, dimmer modules, 24V lighting bus sensors

System Description: Wall-mounted control cabinets for shopping malls and conference rooms, power supply for lighting bus controllers. Low profile fits slim lighting distribution boxes.

Case 6: Test & Measurement / Laboratory Small Tooling

Loads: Test fixture I/O boards, signal conditioning modules, sensor signal transmitters

System Description: Simple production test benches and small laboratory measurement cabinets. Stable 24V DC with low ripple, ideal for transmitter powering.

Selection & Application Limitations (Engineering Key Points)

1. Max continuous output: 31.2W /1.3A, engineering design recommended derate to 80% (≤25W)
2. Derating required when ambient temperature＞61℃; further reduce load for high cabinet temperature
3. Fanless design; reserve ventilation gaps on left/right, do not stack tightly beside circuit breakers
4. NRND legacy model; use DSP30-24/277A2 for new designs; DSP30-24 only for spare replacement on existing equipment
5. Class II double insulation, no PE wire required, simplifies wiring for many wall-mounted low-voltage cabinets, but not applicable for safety loops beyond extra-low voltage safety requirements

Typical Wiring Topology Reference

AC L/N → DSP30-24 → 24V+ /24V→ Parallel loads: PLC/DDC + Sensors + Relay modules; recommend fuse and surge absorber on output side to protect inductive loads such as solenoid valves.

DSP30-24 Engineering Selection Checklist

Applicable for: TDK-Lambda DSP30-24 (24VDC 31.2W, DIN rail, Class II, natural cooling)

Purpose: New project evaluation / field retrofit / spare part verification; legacy NRND model, use DSP30-24/277A2 for new projects

✅ 1. Load Power & Current Verification (Core)

Rated: 24V, 1.3A, 31.2W; recommended 80% derating limit: 25W /1.04A

1. Sum steady-state loads

Sum rated current of all 24V devices: PLC, DDC, sensors, transmitters, relays, gateways, etc.

Inductive loads (solenoid valves, small actuators): inrush current must be considered, not only steady-state value

Total steady-state current ≤1.04A (recommended); short peak up to 1.3A, not continuous

2. Load type restrictions

✅ Suitable: Transmitters, proximity/photoelectric switches, small I/O, RTU, access controllers, DALI gateways

⚠️ Use caution: High-power solenoid valves, large actuators, heating loads, motors

❌ Prohibited: Direct battery float charging (no charge management), high-power LED constant-current boards

3. Output side protection selection

Recommended series fuse at output: 2A slow-blow fuse (24V side)

Inductive loads (solenoid / damper actuators): Freewheeling diode or RC snubber across coil to suppress back EMF and prevent power supply damage

Long cable runs: Add 24V-rated TVS for surge protection

✅ 2. Input Side Verification

1. AC input voltage: 90~264VAC, 47~63Hz; compatible with DC 120~370VDC

Sites with large voltage fluctuation (old factories): Confirm minimum field voltage ≥90VAC

2. Input wiring: L Line, N Neutral; Class II, PE earth not required for power supply

Note: Cabinet shell should connect to protective earth for EMC, power supply itself does not require PE

3. Input inrush current: 25A@115VAC; 50A@230VAC

When multiple power supplies switch on simultaneously in one distribution box, select MCB carefully to avoid tripping at switch-on

✅ 3. Ambient Temperature & Derating Verification (Common Pitfall)

Operating temperature range: -25℃ ~ +71℃

Derating rule: Derating starts above 61℃ at 2.5%/℃

Example: Cabinet temperature 66℃, 5℃ above 61℃ → 12.5% power derating, max available power=31.2×(1-0.125)=27.3W

Engineering recommendation: Reserve extra margin if cabinet temperature＞55℃, ideally keep ≤60℃

1. Installation ventilation requirements

Minimum gap top/bottom ≥10mm; left/right ≥5mm clearance

❌ Do not mount tightly next to heat-generating components such as breakers and contactors

❌ Do not enclose inside fully sealed airtight boxes

2. Storage temperature: -25~+85℃, power off

✅ 4. Mechanical Installation Verification

1. Mounting: Standard 35mm DIN rail, vertical installation (terminals upward)

Horizontal / upside-down mounting not recommended; worsens heat dissipation and accelerates derating

2. Dimensions: W53 × H95.5 × D55.6 mm; preferred for slim cabinets
3. Vibration & shock: Suitable for general industrial and building automation; add rail lock for heavy machinery with high vibration

✅ 5. Protection Function Verification (Fault Modes)

Built-in protections: Fold-back current limiting / short-circuit protection, overvoltage protection, overtemperature protection

Protection behavior: Hiccup mode on some versions; auto-recovery after fault removal

1. Overcurrent: 110~160% rated current, fold-back limiting
2. Overvoltage protection: Trigger at 30~36VDC
3. Overtemperature protection: Shutdown on overtemperature, auto retry after cooling

Note: Repeated short-circuit / thermal cycling shortens service life; output fuse should not be omitted

✅ 6. Status Indicators Verification

DC OK (Green): Output healthy

DC LO (Red): Undervoltage / overload / short-circuit fault

Vout ADJ potentiometer: Output adjustable 24~28VDC

Commissioning tip: Do not turn voltage up to 28V upper limit under no-load; re-measure voltage with load connected to avoid overvoltage damage to transmitters

✅ 7. EMC, Isolation & Safety Verification

1. Isolation rating: Class II double insulation, input-output isolation withstand 3kV AC
2. EMC: EN55032 Class A; immunity meets EN61000-4 (ESD, burst, surge)

⚠️ Class A: For industrial environments; not recommended for residential environments due to EMI non-compliance risk

3. Certifications: UL/CE/UKCA; safety standard EN60950-1
4. Cabling: Route 24V DC cables away from 220V AC power cables to reduce coupling interference

✅ 8. Model Lifecycle Verification (Critical Engineering Reminder)

DSP30-24: NRND Not Recommended for New Design

For repair & replacement on existing equipment: DSP30-24 acceptable

New projects: Upgrade to DSP30-24/277A2, input 90~304VAC, direct DIN rail replacement, verify terminal definition

Alternative domestic models: DR-30-24, LI30-24B24

✅ 9. Site Commissioning Procedure (Power-up Sequence)

1. Disconnect all loads, power supply alone, measure no-load output voltage, trim Vout ADJ to 24V
2. Connect loads gradually, monitor output voltage, temperature rise and LED status
3. Perform short-circuit test (short duration), confirm hiccup protection activates and auto-recovers after fault removal
4. Run full load for 30min, check housing temperature rise for abnormal heating
5. Check voltage drop on long wiring runs; slightly increase output voltage to compensate for cable drop if wire gauge is thin or distance is long

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