Allen-Bradley 1746-P4/A – SLC 500 Series Power Supply Module | Rockwell Automation SLC Platform
Engineering Background
The Allen-Bradley 1746-P4/A is a high-capacity AC power supply module designed for the SLC 500 modular chassis family (1746 series). Engineered by Rockwell Automation, the SLC 500 platform has been a cornerstone of discrete and process control applications across global manufacturing since the 1990s. The 1746-P4/A specifically addresses installations requiring both logic-level (5 VDC) and field-device (24 VDC) power from a single, chassis-integrated supply — eliminating the need for external 24 V power rails in many standard I/O configurations.
Product Positioning
Targeted at maintenance engineers, system integrators, and OEM panel builders who operate or service SLC 500-based control systems, the 1746-P4/A is the preferred replacement supply for 4-slot and larger modular chassis. Its dual-voltage output architecture and wide AC input range make it suitable for both North American (120 VAC) and international (240 VAC) installations without hardware modification.
Complete Technical Specifications
| Parameter | Specification |
|---|---|
| Catalog Number | 1746-P4 / 1746-P4/A |
| Platform | Allen-Bradley SLC 500 (1746 Modular Chassis) |
| Input Voltage | 85–264 VAC, 47–63 Hz (universal AC input) |
| Input Current | 3.0 A @ 120 VAC / 1.5 A @ 240 VAC |
| Output – 5 VDC | 10 A (logic bus) |
| Output – 24 VDC | 0.46 A (field device / sensor power) |
| Total Output Power | 58 W (5 VDC × 10 A + 24 VDC × 0.46 A) |
| Backplane Connector | SLC 500 1746-series chassis backplane |
| Operating Temperature | 0 °C to +60 °C |
| Storage Temperature | -40 °C to +85 °C |
| Relative Humidity | 5–95% non-condensing |
| Dimensions (H × W × D) | Occupies 1 slot in 1746 chassis |
| Weight | Approx. 1.1 kg |
| Agency Certifications | UL Listed, CE Marked, CSA Certified |
| Enclosure Rating | Open type (chassis-mounted) |
| Fuse | Internal, non-user-replaceable |
| LED Indicators | POWER (green) — indicates DC output healthy |
Proven Application Environments
- Discrete Manufacturing — Assembly lines, conveyor control, and machine tool automation using SLC 5/03, 5/04, or 5/05 processors
- Process Control — Batch processing, pump/valve sequencing, and PID loop control in chemical and water treatment plants
- Material Handling — Sortation systems, palletizers, and automated storage/retrieval systems (AS/RS)
- Building Automation — HVAC control panels and facility management systems with legacy SLC 500 infrastructure
- OEM Machine Panels — Packaging machinery, printing presses, and food processing equipment requiring a compact, reliable power source
- Retrofit & Maintenance — Direct drop-in replacement for failed 1746-P4 units in existing installed base without chassis or wiring changes
Engineering Advantages
- Universal AC Input (85–264 VAC) — Single SKU supports both 120 VAC and 240 VAC sites; no jumper or tap selection required
- Dual-Voltage Output — Integrated 24 VDC output eliminates external power supplies for sensors and field devices in many applications, reducing panel footprint and wiring complexity
- High 5 VDC Current Capacity (10 A) — Supports fully populated 4-slot chassis with high-density I/O modules and processor without derating
- Chassis-Integrated Design — Backplane-mounted form factor ensures clean power distribution with minimal impedance; no external cabling between supply and chassis
- Robust Thermal Design — Rated to +60 °C ambient; suitable for non-air-conditioned industrial enclosures in warm climates
- Regulatory Compliance — UL, CE, and CSA certifications satisfy safety requirements for North American and European installations
System Architecture & Signal Flow
The 1746-P4/A occupies the leftmost slot of any 1746-series modular chassis (4-slot, 7-slot, 10-slot, or 13-slot). AC mains power enters via the terminal block on the supply faceplate. Internally, the switching power supply converts AC input to regulated 5 VDC and 24 VDC DC rails. The 5 VDC bus is distributed across the chassis backplane to all installed modules (processor, I/O, and communication modules). The 24 VDC output is available at dedicated terminals on the supply faceplate for direct connection to field sensors, proximity switches, or solenoid valve pilots rated ≤ 0.46 A total.
The POWER LED on the faceplate illuminates green when both DC outputs are within regulation. Loss of the LED indicates an input power fault, blown internal fuse, or output overload condition — triggering a controlled processor fault and safe system shutdown.
Sourcing & Quality Verification
- Origin: Sourced from authorized distributors and verified industrial surplus channels
- Inspection Protocol: Each unit undergoes visual inspection, label verification (catalog number, series, date code), and functional power-on test prior to shipment
- Authenticity: Catalog number, series letter, and Rockwell Automation branding verified against OEM documentation
- Condition Options: New-in-box (NIB), factory-refurbished, and tested-used grades available — condition stated explicitly in each listing
- Packaging: Anti-static bag + foam-lined carton; meets IEC 61340-5-1 ESD protection requirements for sensitive electronics
Procurement Process
- Confirm Compatibility — Verify your chassis catalog number (e.g., 1746-A4, 1746-A7, 1746-A10, 1746-A13) and current power supply slot occupancy
- Select Condition & Quantity — Choose NIB, refurbished, or tested-used based on project budget and criticality; contact us for volume pricing on 5+ units
- Place Order — Add to cart and complete checkout; HKD pricing displayed; multi-currency checkout available
- Order Confirmation — Automated confirmation email with order number and estimated ship date within 1 business day
- Shipping — DHL Express / FedEx International Priority standard; lead time 3–7 business days to most destinations; expedited options available on request
- Documentation — Certificate of conformance, test report, and commercial invoice provided upon request for customs and quality records
Technical FAQ
Q: Is the 1746-P4/A compatible with all SLC 500 chassis sizes?
A: Yes. It is compatible with all 1746-series modular chassis (4, 7, 10, and 13-slot). It is not compatible with the SLC 500 fixed (1747-L20/L30/L40) controllers, which have integrated power supplies.
Q: Can the 1746-P4/A replace a 1746-P2 or 1746-P3?
A: Physically yes — all 1746-P series supplies use the same chassis slot and backplane connector. However, verify that the P4/A’s 10 A / 5 VDC output meets or exceeds your chassis power budget. The P4/A is the highest-output standard supply in the 1746-P series and is a safe upgrade from P2 (5 A) or P3 (8 A) units.
Q: What causes the POWER LED to go off during operation?
A: Common causes include: (1) AC input power loss or voltage sag below 85 VAC, (2) chassis overload exceeding 10 A on the 5 VDC bus, (3) internal thermal shutdown due to blocked ventilation, or (4) end-of-life internal fuse failure. Check input voltage, remove non-essential modules to reduce load, and ensure minimum 50 mm clearance above and below the chassis for airflow.
Q: Is a 24 VDC external supply still needed with the 1746-P4/A?
A: For field devices drawing ≤ 0.46 A total from the 24 VDC terminal, no external supply is needed. Applications with higher 24 VDC demand (e.g., multiple solenoids or large sensor networks) will still require a supplemental 24 VDC power supply wired externally.
Q: What is the typical service life of the 1746-P4/A?
A: Rockwell Automation rates the SLC 500 platform for a minimum 10-year service life under normal operating conditions. Electrolytic capacitors in the switching supply are typically the life-limiting component; units operating continuously at elevated temperatures (>50 °C) may exhibit reduced MTBF. Konmask recommends proactive replacement at 10–15 years of service or upon first indication of output voltage instability.
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