Allen-Bradley 1746-P1 SLC 500 Power Supply Overview

The Allen-Bradley 1746-P1 is an SLC 500 power supply from Rockwell Automation. This module provides backplane power for all modules in a 1746 chassis. It has a nominal input voltage of 120/220 Volts AC with a frequency range of 47 to 63 Hertz. The 1746-P1 supplies internal current capacity of 2 A at 5 V DC and 0.46 A at 24 V DC to the backplane. It also provides a 24 V DC user output with 200 mA capacity and built-in fuse protection. This power supply must be installed at the leftmost slot of any SLC 500 chassis. Only one power supply is needed per chassis.

Input Specifications

The Allen-Bradley 1746-P1 accepts a wide range of AC input voltages. Line voltage can be 85 to 132 Volts AC or 170 to 265 Volts AC depending on jumper configuration. Input frequency spans 47 to 63 Hz for global compatibility. Typical line power requirement is 135 VA with maximum input power of 42 Watts. Inrush current reaches a maximum of 20 Amps during power-up. Consequently, use appropriate circuit protection rated for this inrush current.

Output Specifications

The Allen-Bradley 1746-P1 delivers reliable DC power to the backplane and user devices. Backplane current capacity is 2 Amps at 5 V DC for logic circuits. Backplane current capacity at 24 V DC is 0.46 Amps for output modules. User-power current capacity is 200 mA at 24 V DC with a voltage range of 18 to 30 Volts DC. The maximum user-supplied overcurrent protection should be rated at 15 Amps. Therefore, the 1746-P1 supports both backplane and external load requirements.

CPU Hold-Up Time & Undervoltage Protection

The Allen-Bradley 1746-P1 includes a valuable hold-up time feature. During an input power drop, the CPU continues operating for a limited period. The CPU hold-up time is 20 ms at full load. At no load, the hold-up time extends to 3000 ms (3 seconds) . If power returns to normal voltage during this period, the processor may continue normal operation without interruption. If undervoltage persists beyond the hold-up time, the 1746-P1 stops supplying power to the controllers. Operations resume automatically once normal input voltage returns.

Fuse Protection & Overcurrent Behavior

The Allen-Bradley 1746-P1 comes with built-in fuse protection. The internal fuse (part number 1746-F1 or equivalent) guards against fire hazards due to short-circuit conditions. However, overcurrent behavior differs based on manufacturing origin. For Series A units made in Japan, a user-power overcurrent condition causes power supply shutdown and a CPU fault. Recovery requires reloading the user program. For Series A units made in Malaysia, the CPU continues running but the 24 V DC user output shuts down. Recovery requires correcting the overcurrent condition only.

Isolation & Environmental Specifications

The Allen-Bradley 1746-P1 provides robust isolation for safety and noise immunity. Isolation between input terminals and the backplane is 1800 Volts AC RMS for 1 second. Operating temperature ranges from 0 to 60 degrees Celsius. Above 55°C, the current capacity is derated by 5% . Therefore, consider derating in high-temperature environments. Dimensions are 5.5 x 2.3 x 5.7 inches (H x W x D). Weight is 2 pounds (0.9 kilograms) .

Installation Guidelines

Follow these steps to install the Allen-Bradley 1746-P1 correctly. First, ensure the chassis is completely powered down before installation. Second, set the input voltage jumper for either 120V or 220V AC operation. This step is critical because exposed pins have hazardous voltage when power is applied. Third, install the 1746-P1 in the leftmost slot of the 1746 chassis. Fourth, secure the module with the retaining screws at top and bottom. Fifth, connect the AC input power to the designated terminals. Finally, apply power and verify normal operation.

Do not apply power before setting the input voltage jumper. Use a user-supplied overcurrent protection device rated at 15 Amps maximum. The 1746-P1 requires proper grounding for safe operation.

Package Contents

Your shipment includes the following items:

• 1 x Allen-Bradley 1746-P1 SLC 500 power supply

• 1 x Installation instructions sheet

• 1 x Input voltage jumper (pre-installed, position may vary)

No fuse is included with the 1746-P1 beyond the internal installed fuse. Therefore, order replacement fuse 1746-F1 separately if needed. No power cord is provided.

Frequently Asked Questions (FAQ)

1. What is the difference between the 1746-P1 and 1746-P2?
The 1746-P1 has 2A at 5V and 0.46A at 24V. The 1746-P2 has higher current capacity (5A at 5V). Choose based on your chassis loading requirements.

2. Can I install this power supply in an expansion chassis?
Yes. The Allen-Bradley 1746-P1 installs in the leftmost slot of main, expansion, or remote I/O racks. Each chassis requires its own power supply.

3. What is the CPU hold-up time for this power supply?
The 1746-P1 provides 20 ms hold-up time at full load. At no load, the hold-up time extends to 3000 ms (3 seconds).

4. How do I recover from a user-power overcurrent condition?
Recovery depends on the manufacturing origin of your 1746-P1. Japanese units require program reload; Malaysian units only need the overcurrent condition corrected.

5. What is the isolation voltage rating?
The Allen-Bradley 1746-P1 provides 1800 Volts AC RMS isolation for 1 second between input terminals and the backplane.

Why Choose the Allen-Bradley 1746-P1?

This SLC 500 power supply delivers reliable backplane power for small to medium systems. For starters, the Allen-Bradley 1746-P1 accepts both 120V and 220V AC inputs for global use. The 2A at 5V DC and 0.46A at 24V DC backplane capacity supports typical SLC 500 configurations. In addition, the 200 mA user-power output at 24V DC powers small field devices directly. The 20 ms CPU hold-up time at full load protects against brief power interruptions. At no load, the hold-up time extends to 3 seconds for even greater protection. The 1800V AC isolation ensures safety and noise immunity. Furthermore, the 1746-P1 includes built-in fuse protection against short-circuit fire hazards. The derating above 55°C allows operation in warmer industrial environments. Most importantly, this power supply integrates seamlessly into the leftmost slot of any SLC 500 chassis.

Order the Allen-Bradley 1746-P1 today for your SLC 500 power needs. Specifically, this power supply is perfect for small to medium SLC 500 systems, main racks, expansion chassis, and remote I/O racks requiring reliable 5V and 24V DC backplane power.