Allen-Bradley 1756-OA8 ControlLogix AC Output Module 8-Point
Introduction:
The 1756-OA8 is a digital AC output module for ControlLogix systems. It provides 8 outputs (74-265VAC) in two groups of four, with 2A per point at 60°C.
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Product Overview
The 1756-OA8 belongs to the ControlLogix Series. Its product type is a Digital AC Output Module. The product classification is I/O Modules. The current price for this item is ¥3,280 RMB, and the product gross weight is 0.38 kg.
Rockwell Automation designed this module under the Allen-Bradley brand for the ControlLogix platform. The 1756-OA8 features eight (8) output channels organized as two groups of four (4) channels each . This module operates at voltage categories of 74 to 265V AC with a frequency range of 47 to 63 Hz . It installs directly into any 1756 local or remote chassis. Therefore, this output module suits both stand-alone and distributed I/O topologies.
Technical Specifications
Output Channels and Grouping
The module provides 8 output points organized as two I/O groups with 4 channels per group. Channel grouping allows each group to operate at different voltage levels (both must be AC). For example, one group may operate at 120V AC while the other operates at 240V AC. The terminal commons are not internally connected, providing isolation during troubleshooting.
Voltage Ratings
The nominal voltage category spans 120 to 240 Volts AC . The operating voltage range extends from 74 to 265 Volts AC at 47 to 63 Hz . This wide range accommodates various global power systems. The frequency tolerance covers both 50 Hz and 60 Hz systems.
Current Ratings
At 60°C , each output point handles 2 Amps maximum. The maximum current per group at 60°C is 2 Amps . The maximum current per module reaches 5 Amps at 30°C with linear derating to 4 Amps at 60°C . The surge current rating per point is 20 Amps for 43 milliseconds , repeatable every 2 seconds at 60°C. The minimum load current per point is 10 milliamps . The off-state maximum leakage current is 3 milliamps per point .
Output Delay Time
The output delay time is programmable based on line frequency. At 60 Hz , the delay measures 9.3 milliseconds (off to on and on to off). At 50 Hz , the delay measures 11 milliseconds . These delays synchronize with the AC line cycle for optimal performance.
Fault and Program Modes
The States in Fault mode per point can hold the last state (both on-state and off-state). Similarly, the States in Program mode per point can hold the last state. This flexibility allows safe system behavior during communication loss or programming changes.
Scheduled Outputs
The module supports synchronization within 16.7 seconds for scheduled outputs . This feature enables coordinated output timing across multiple modules.
Backplane Current and Power
The backplane current draw at 5 Volts is 200 mA . At 24 Volts , the draw is 2 mA . Total backplane power rating is 1.07 Watts . Maximum power dissipation reaches 5.1 Watts at 60°C . Thermal dissipation is 17.39 BTU per hour .
Isolation Voltage
The isolation voltage rating is 50 Volts continuous . This isolation protects the backplane and controller from field wiring faults.
Compatible Removable Terminal Blocks
Compatible removable terminal blocks include 1756-TBNH and 1756-TBSH . These RTBs provide convenient termination points for field wiring. With the RTB, signals can be wired without the actual module present. This design allows quick module replacement without rewiring.
Chassis Compatibility
Compatible ControlLogix chassis include 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17 . The module supports local or remote I/O chassis installation.
External Fusing Recommendation
This module does not come with fused channels . Therefore, install external fusing to provide module protection. Fuse sizing should reference the current rating per point (2A at 60°C). External fuses protect both the module and connected field devices.
Typical Applications
Output modules energize various electrical components. Typical loads include solenoids, relays, pilot lamps, sirens, horns, buzzers, annunciator panels, motors, and contactors .
Compatibility
The 1756-OA8 is compatible with any ControlLogix processor. It also works with any ControlLogix communication module, including encompass partner modules. It may also work alongside GuardLogix safety modules.
Installation Guide
Follow these steps to install your 1756-OA8 correctly.
Power Down the Chassis: Disconnect power from the ControlLogix chassis completely. This prevents electrical shock and module damage.
Select a Slot: Choose an available slot in the ControlLogix chassis. The 1756-OA8 occupies one slot.
Insert the Module: Align the 1756-OA8 with the slot guides. Push firmly until the module seats into the backplane connector.
Secure the Module: Tighten the retaining screws at the top and bottom. This secures the output module in place.
Wire the Terminal Block: Connect your AC loads to the appropriate terminals on the 1756-TBNH or 1756-TBSH terminal block. Install external fuses on each output for protection.
Install the Terminal Block: Plug the wired terminal block into the front of the 1756-OA8 . Ensure it seats fully and locks in place.
Apply Power: Restore power to the ControlLogix chassis. Verify the module powers up without errors.
Configure Outputs: Use Studio 5000 programming software to configure the output module. Set output delay times based on your line frequency (50 Hz or 60 Hz).
Test Operation: Energize each output channel individually. Confirm that each connected load responds correctly.
Package List
1 x 1756-OA8 ControlLogix Digital AC Output Module (8-point)
2 x Module retaining screws (pre-installed)
1 x Installation instruction manual
*Note: Removable terminal block (1756-TBNH or 1756-TBSH), external fuses, and field wiring are sold separately.*
Frequently Asked Questions (FAQ)
1. What voltage and frequency ranges does the 1756-OA8 support?
The module operates from 74 to 265V AC with a frequency range of 47 to 63 Hz . This covers both 50 Hz and 60 Hz systems worldwide. The nominal voltage category is 120-240V AC.
2. What is the current rating per output point?
At 60°C , each output point handles 2 Amps maximum. The surge rating is 20 Amps for 43 milliseconds , repeatable every 2 seconds. The minimum load current is 10 milliamps .
3. Can the two output groups operate at different voltages?
Yes, the two groups (4 points each) can operate at different AC voltage levels. The terminal commons are not internally connected , providing isolation between groups. One group may run at 120V AC while the other runs at 240V AC.
4. Does the 1756-OA8 have built-in fusing?
No, this module does not have fused channels . Install external fuses on each output for module protection. Size fuses based on the 2A current rating per point at 60°C.
5. What is the output delay time for this module?
The delay is programmable based on line frequency. At 60 Hz , delay is 9.3 milliseconds . At 50 Hz , delay is 11 milliseconds . These delays synchronize with the AC line cycle for optimal performance.