Purchase now: Allen-Bradley 1756-PB72 Power Supply
Purchase now: Atlantechdrives provides you the 1756-PB72, a highly robust, industrial-grade 24V DC standard power supply meticulously engineered by Rockwell Automation exclusively for the ControlLogix 1756 programmable automation controller (PAC) system. The power supply is the absolute literal heartbeat of any PLC architecture, and the 1756-PB72 is designed to deliver incredibly clean, stable, and uninterrupted power to the high-speed internal backplane. Rather than directly powering field devices, this specific power supply takes incoming 24V DC line power from the factory (typically generated by an external bulk power supply like a SolaHD or an Allen-Bradley 1606-XLS) and converts it into the highly regulated 1.2V, 3.3V, 5.1V, and 24V DC currents required by the ControlLogix CPU, communication bridges, and I/O modules resting in the chassis. This module mounts strictly on the far-left side of standard 1756-A4, A7, A10, A13, or A17 chassis, and is universally deployed in control cabinets where maintaining a 24V DC control power architecture is required for safety and battery-backup (UPS) reasons.
Technical Specifications of the 1756-PB72
The 1756-PB72 is a standard (non-redundant) power supply designed to provide a maximum backplane output power of 75 Watts. It features built-in overcurrent and overvoltage protection to shield the delicate and expensive ControlLogix processor from incoming electrical anomalies.
- Part Number: 1756-PB72
- Platform: ControlLogix 1756 System
- Input Voltage Range: 18…32V DC
- Nominal Input Voltage: 24V DC
- Maximum Input Power: 95 Watts
- Maximum Output Power (Backplane): 75 Watts
- Current Capacity at 5.1V DC: 10 Amps
- Current Capacity at 24V DC: 2.8 Amps
Expert Tips: Backplane Power Calculation and Overloading
A catastrophic engineering mistake frequently made during the design phase of a new automation panel is failing to calculate the backplane power consumption. Expert Tip: Just because a 1756 chassis has 13 empty slots does not mean the 1756-PB72 can power 13 modules. High-performance modules, such as the 1756-L85E processor, 1756-EN3TR fiber network bridges, and massive 32-point isolated analog output cards, draw heavily from the 5.1V and 24V backplane traces. The 1756-PB72 provides a strict maximum of 10 Amps at 5.1V DC. If you fill a chassis with power-hungry modules and exceed this 10 Amp limit, the power supply will instantly enter a thermal or overcurrent protection shutdown, crashing the entire PLC and halting the factory. Always utilize Rockwell’s Integrated Architecture Builder (IAB) software prior to purchasing to digitally build your rack and verify that your selected modules do not exceed the 75W maximum capacity of the PB72.
Installation Advice: Input Wiring and Redundancy Limits
When wiring the incoming 24V DC power to the front terminal block of the 1756-PB72, you must use correctly sized copper wire (typically 14 AWG or 12 AWG) to minimize voltage drop across long control cabinet runs. Furthermore, automation engineers must clearly understand that the 1756-PB72 is a standard power supply. It cannot be used in a chassis power redundancy setup. If your critical infrastructure requires two power supplies sharing the load on a single chassis (so if one fails, the other takes over seamlessly), you cannot use the PB72. You must specifically purchase the 1756-PB75R (the «R» stands for Redundant) along with the corresponding redundant power supply chassis adapter.
Frequently Asked Questions (FAQs)
Q: Does the 1756-PB72 provide 24V DC power to my field sensors and solenoid valves?
A: No. The 1756-PB72 strictly powers the internal ControlLogix backplane and the silicon circuitry of the modules themselves. You must route separate 24V DC field power from your external bulk power supply to the Removable Terminal Blocks (RTBs) of your input and output modules to power physical field devices.
Q: How do I know if the power supply is functioning correctly?
A: The 1756-PB72 features a prominent green LED on the front faceplate. If this light is solid green, the supply is outputting the correct backplane voltages. If it is off or flashing red while input power is applied, the unit has detected an internal fault or a severe backplane short circuit.
Do you need more references from this brand? Explore our full catalog of Allen-Bradley here.
This 12/24V DC power supply is the standard choice for providing stable backplane current to a 1756-A10 10-slot chassis.
