Allen-Bradley 1746-P2 SLC 500 Power Supply 5A

1746-P2 Power Supply by Allen-Bradley for SLC 500

Product Introduction

The Allen-Bradley 1746-P2 is a high-output power supply designed specifically for the SLC 500 platform. This module provides substantial backplane power, making it the preferred choice for larger racks that host numerous I/O modules and communication adapters.

This power supply accepts a wide input voltage range from 85 to 265 VAC at 47–63 Hz, ensuring global compatibility. Its key strength lies in its internal current capacity: 5 A at 5 VDC and 0.96 A at 24 VDC for the backplane. Additionally, it offers a user-power output of 24 VDC with a capacity of 200 mA, suitable for powering external field devices.

A built-in fuse (replaceable with the 1746-F1 kit) provides protection against short-circuit hazards. Furthermore, the module features 1800 Volts AC RMS isolation between the input terminals and the backplane, which significantly enhances electrical safety and noise immunity in industrial environments.

Technical Specifications

The 1746-P2 power supply is engineered to handle high current loads with exceptional stability. Its detailed specifications are as follows:

• Input Voltage: 85 to 132 VAC or 170 to 265 VAC (jumper-selectable)

• Input Frequency: 47 to 63 Hz

• Input Power: 70 Watts (typical) / 180 VA

• Inrush Current: 20 Amps (maximum)

• Internal Current Capacity: 5 A at 5 VDC and 0.96 A at 24 VDC

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

• Backplane Current (5V): 5 Amps

• Backplane Current (24V): 0.96 Amps

• Isolation: 1800 Volts AC RMS for 1 second

• Fuse Protection: Uses 1746-F1 or an equivalent replacement

• Terminals: Accommodates up to two AWG wires per terminal

This module installs exclusively in the leftmost slot of a 1746 chassis. Notably, its slot position is not counted in the rack's slot numbering; the processor or communication adapter occupies Slot 0. Only one power supply is required per chassis.

Mechanical and Environmental Parameters

The 1746-P2 features a slightly wider profile than lower-power models to accommodate its higher output capacity. Its compact yet robust construction ensures reliable performance in harsh industrial settings.

• Dimensions (H x W x D): 5.5 x 3.3 x 5.7 inches (140 x 84 x 145 mm)

• Weight: 2.5 pounds (1.1 kilograms)

• Operating Temperature: 0 to 60 °C

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

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

Installation Guidelines

Correct installation of the 1746-P2 is essential for safety and system reliability. Follow these steps carefully:

1. Set the Input Jumper: Before connecting power, verify the voltage selector jumper matches your line voltage (100/120V or 200/240V). Exposed pins become hazardous when power is applied.

2. Mount in the Chassis: Secure the module in the leftmost slot of the SLC 500 chassis using the provided mounting screws.

3. Connect Wiring: Attach the AC line, neutral, and ground wires to the appropriate terminals. Each terminal accepts up to two AWG wires.

4. Apply Overcurrent Protection: For the user-power circuit, ensure external protection does not exceed 15 A.

Safety Note: Always disconnect input power before connecting or disconnecting wires. Active connections can produce electric arcs that may damage the electronic backplane. Additionally, consider using an isolation transformer if your installation involves high-inductive loads that could cause voltage surges.

The 1746-P2 provides a CPU hold-up time of 20 ms at full load and 3000 ms at no load. During brief undervoltage events, the processor continues scanning I/O data. If input voltage remains low beyond the hold-up period, the module shuts down but automatically restores operation when normal voltage returns.

Overcurrent Behavior by Series Revision

It is important to note the behavior differences across revisions:

• Series A and B: A power supply shutdown and CPU fault occur during user-power overcurrent. Recovery requires reloading the user program.

• Series C: Only the 24 VDC user-output shuts down while the CPU continues running. Recovery simply involves correcting the overcurrent condition.

Packaging List

Your shipment includes the following items:

• (1) Allen-Bradley 1746-P2 Power Supply Module

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

• (1) Input voltage selection jumper (pre-installed on the board)

Frequently Asked Questions (FAQ)

1. What is the main difference between the 1746-P1 and the 1746-P2?
The 1746-P2 offers significantly higher backplane current capacity. It provides 5 A at 5 VDC and 0.96 A at 24 VDC, compared to the 1746-P1 which delivers 2 A and 0.46 A respectively. This makes the 1746-P2 better suited for larger racks with more modules.

2. Can I use the 1746-P1 fuse (1746-F1) for this model?
Yes, the 1746-P2 uses the same fuse protection kit, part number 1746-F1, or an equivalent replacement.

3. What should I do if the user-power output experiences an overcurrent?
For Series A or B units, the power supply shuts down and you must reload the user program after correcting the fault. For Series C units, simply correct the overcurrent condition; the CPU will continue running without program loss.

4. How many 1746-P2 power supplies can I install in one chassis?
Only one power supply is required and supported per SLC 500 chassis. It must be installed in the leftmost slot, which is not counted in the slot numbering.

5. Why is the 1746-P2 wider than other SLC power supplies?
The 1746-P2 has a wider profile (3.3 inches) to accommodate its larger internal components, which are necessary to deliver the higher 5 A backplane current. It still fits the standard 1746 chassis without issues.