Allen-Bradley 1746-P3 SLC 500 DC Power Supply

1746-P3 Power Supply by Allen-Bradley for SLC 500

Product Introduction

The Allen-Bradley 1746-P3 is a DC-powered supply module tailored for the SLC 500 control system. Unlike its AC-input counterparts, this unit operates directly from a 24 VDC source, making it perfect for applications that utilize DC distribution panels, battery plants, or renewable energy sources.

This module mounts in the leftmost position of the 1746 chassis and does not consume a numbered slot. It converts the incoming DC voltage into stable backplane power, delivering 3.6 A at 5 VDC and 0.87 A at 24 VDC to support all connected I/O and processor modules. Furthermore, it provides a user-power output of 24 VDC at 200 mA for external field devices.

The 1746-P3 features built-in fuse protection (replaceable with the 1746-F3 kit) to guard against short-circuit conditions. Additionally, its design includes 600 Volts AC RMS dielectric withstand capability between the chassis ground and input terminals for enhanced safety in industrial environments.

Technical Specifications

The 1746-P3 power supply is engineered for reliable operation in DC-powered industrial settings. Its comprehensive specifications are listed below:

• Nominal Input Voltage: 24 VDC

• Input Voltage Range: 19.2 to 28.8 VDC

• Input Power: 61 Watts (typical) / 90 VA

• Inrush Current: 20 Amps (maximum)

• Internal Current Capacity: 3.6 A at 5 VDC and 0.87 A at 24 VDC

• User-Power Output: 24 VDC at 200 mA (range: 18 to 30 VDC)

• Backplane Current (5V): 3.6 Amps

• Backplane Current (24V): 0.87 Amps

• Isolation (Version B or later): 600 Volts AC RMS for 1 second (between chassis ground and input terminals; no isolation between backplane and input)

• Fuse Protection: Uses 1746-F3 or equivalent (e.g., BUSSMAN AGC 5 or Nagasawa ULCS-61ML-5)

• Terminals: Accommodates up to two AWG wires per terminal

This module is certified for hazardous locations, holding UL and C-UL listings for Class 1, Division 2, Groups A, B, C, D. It is also rated for Pollution Degree 2 environments and Category II installation applications.

Mechanical and Environmental Parameters

The 1746-P3 features a compact and rugged design suitable for demanding industrial conditions. Its physical and environmental specifications are as follows:

• Dimensions (H x W x D): 5.5 x 2.9 x 5.7 inches (139.7 x 79.2 x 144.8 mm)

• Weight: 2.5 pounds (1.1 kilograms)

• Operating Temperature: 0 to 60 °C (32 to 140 °F)

• Derating: Current capacity is derated by 5% when the ambient temperature exceeds 55 °C (131 °F).

• Altitude: Suitable for operation up to 2000 meters without derating

• Enclosure Type: Open-type (requires installation within a protective chassis)

Installation Guidelines

Proper installation of the 1746-P3 ensures safe and reliable system operation. Follow these steps carefully:

1. Mount in the Chassis: Secure the module in the leftmost slot of the SLC 500 chassis using the provided mounting screws. Only a 1/8-inch flat head and a 1/4-inch Phillips head screwdriver are required.

2. Connect DC Power Wiring: Attach the positive (+), negative (-), and ground wires to the designated terminals. Each terminal accepts up to two AWG wires.

3. Verify Polarity: Double-check DC polarity before applying power. Reverse polarity can damage the module or connected components.

4. Protect Against ESD: Keep the module in static-shield packaging when not in use. Avoid touching the connector pins, backplane connector, or circuit components.

Safety Note: Always disconnect input power before connecting or disconnecting wires. The 1746-P3 provides a CPU hold-up time of 5 ms at full load and 1000 ms at no load, allowing the processor to ride through brief power interruptions.

Important Revision Note

For Version B or later units, the 1746-P3 provides 600 Volts AC RMS isolation between the chassis ground terminal and input terminals. Earlier versions lack this isolation feature. Always verify your unit's revision level for accurate safety planning.

Packaging List

Your shipment includes the following items:

• (1) Allen-Bradley 1746-P3 Power Supply Module

• (1) User manual and installation guide (digital copy)

• (1) Pre-installed input terminal block

Frequently Asked Questions (FAQ)

1. What type of input power does the 1746-P3 require?
The 1746-P3 requires a DC input voltage between 19.2 and 28.8 VDC, with a nominal rating of 24 VDC. It is not compatible with AC mains power.

2. Which fuse should I use for replacement?
Use the recommended Allen-Bradley 1746-F3 fuse kit or an equivalent such as the BUSSMAN AGC 5 or Nagasawa ULCS-61ML-5 fuse. Always verify the fuse rating matches your application wiring.

3. Does the 1746-P3 provide isolation between input and backplane?
No, there is no isolation between the input terminals and the backplane. However, Version B or later units provide 600 Volts AC RMS dielectric withstand between the chassis ground terminal and input terminals.

4. What is the CPU hold-up time for this module?
The 1746-P3 offers a hold-up time of 5 milliseconds at full load and up to 1000 milliseconds at no load, enabling the processor to maintain operation during brief voltage dips.

5. Is this module suitable for hazardous locations?
Yes, the 1746-P3 is UL and C-UL listed for Class 1, Division 2, Groups A, B, C, D hazardous locations, making it suitable for use in potentially explosive environments when properly installed.