Allen-Bradley 1391-DES45-DI-AQB Replacement Solution

Product Overview

Allen-Bradley 1391-DES45-DI-AQB Replacement Solution: Seamless Transition from Legacy 1391 Series Servo Drives

The Allen-Bradley 1391-DES45-DI-AQB is a 45A digital servo drive from Rockwell Automation’s 1391 Series, designed for high-performance motion control in demanding industrial environments. As this model reaches end-of-life and spare parts become increasingly scarce, many facilities running legacy servo systems — including older 1391-DES, 1391-BDES, and 1391-ES variants — are now facing urgent replacement and modernization decisions. TOPNLMS stocks verified 1391-DES45-DI-AQB units and provides full migration support to help your team execute a smooth, low-downtime transition.

Whether your plant operates a multi-axis CNC cell, a packaging line, a press brake, or a conveyor system built around the 1391 Series platform, this guide covers the critical compatibility factors: wiring pinouts, AQB encoder interface, power supply requirements, communication architecture, cabinet space, and commissioning steps — so your engineering team can plan the retrofit with confidence.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful 1391-DES45-DI-AQB retrofit rarely involves the drive alone. In practice, your migration team will also need to address the surrounding system components to ensure a fully integrated, reliable result. During the upgrade process, engineers commonly work with the following components:

On the controller side, the 1391-DES45-DI-AQB interfaces directly with Allen-Bradley 1756-M02AE or 1756-M08SE servo motion modules installed in a ControlLogix chassis, or with a 1747-SCNR ScanPort adapter in legacy SLC 500 systems. If your existing rack uses a 1756-L71 or 1756-L73 ControlLogix controller, the drive’s digital command interface can be mapped through the motion axis configuration in Studio 5000 Logix Designer without requiring a full program rewrite — only axis parameter tuning is needed.

For power distribution within the control cabinet, the drive requires a properly rated 1606-XLP power supply or equivalent 24VDC logic supply for the control board, alongside the main 3-phase AC bus. If your cabinet uses a 1321-3R line reactor upstream of the drive, this can typically be retained, as the 1391-DES45-DI-AQB is compatible with standard AC line conditioning equipment used across the 1391 family.

On the feedback side, the AQB encoder interface accepts standard A-Quad-B incremental encoder signals. If the existing servo motor — such as an MPL-B430P or MPL-B540K Allen-Bradley servo motor — is already equipped with an AQB encoder, the existing encoder cable and connector can be reused directly, significantly reducing rewiring time. For axes previously using resolver feedback, a 1391-ACNR resolver-to-encoder converter or a motor swap to an AQB-equipped unit will be required.

At the I/O level, if your system uses a 1734 POINT I/O or 1769 Compact I/O module rack for digital interlocks and drive enable/fault signals, these remain fully compatible with the 1391-DES45-DI-AQB’s digital I/O interface. Signal isolation between the drive’s fault output and the PLC input card can be handled with a 1492-IFM20F interface module or equivalent signal conditioner, which is recommended in high-noise environments such as press rooms or welding cells.

For commissioning and parameter backup, a 1203-USB or 1203-GK5 programming cable connected to the drive’s ScanPort interface allows direct parameter upload/download using DriveExplorer or DriveExecutive software. Backing up the existing drive parameters before removal and restoring them to the replacement unit is strongly recommended to minimize tuning time during startup.

Retrofit Guidance FAQ

Q: Can I reuse my existing motor power cables when replacing the 1391-DES45-DI-AQB?
A: In most cases, yes. The 1391-DES family uses a consistent TB1 motor power terminal layout. Verify wire gauge and insulation rating against the replacement unit’s nameplate current rating. If the original installation used shielded motor cable with a proper ground drain, this can be retained without modification.

Q: Will my existing PLC program need to be rewritten?
A: No full rewrite is required for a like-for-like 1391-DES45-DI-AQB replacement. If replacing a same-SKU unit, only axis tuning parameters (Kp, Ki, velocity feedforward) may need re-optimization after installation. If migrating from an earlier 1391-ES or analog-command variant, the motion command interface may differ and a partial program update may be needed to map digital command words correctly.

Q: Is the AQB encoder interface compatible with my existing servo motor?
A: The 1391-DES45-DI-AQB accepts standard A-Quad-B incremental encoder signals (typically 1024 or 2048 PPR). If your motor uses a resolver, you will need either a resolver-to-encoder converter module or a motor replacement. Confirm the encoder specification on your motor nameplate before ordering.

Q: How much physical space does the replacement drive require in the control cabinet?
A: The 1391-DES45-DI-AQB shares the same panel-mount footprint as other 1391-DES series drives. In most installations, the replacement unit mounts directly to the existing mounting plate without requiring cabinet modifications. Allow adequate clearance above and below the drive for airflow per the 1391 installation manual.

Q: What communication protocols does this drive support?
A: The 1391-DES45-DI-AQB uses a digital I/O command interface and ScanPort for parameter access. It does not natively support EtherNet/IP or DeviceNet as a network node. Integration with a ControlLogix or SLC 500 system is achieved through analog/digital command signals and motion module configuration, not a fieldbus connection from the drive itself.

Q: What is the recommended procedure for replacing a failed 1391-DES45-DI-AQB in a live production environment?
A: (1) Back up existing drive parameters via ScanPort using DriveExplorer. (2) De-energize and lock out the drive per LOTO procedures. (3) Label and photograph all wiring connections before removal. (4) Install the replacement unit and restore wiring per the original layout. (5) Restore parameters from backup. (6) Perform a no-load jog test before returning the axis to production. (7) Monitor for fault codes during the first production cycle.

Warranty Assurance

Every 1391-DES45-DI-AQB unit shipped by TOPNLMS is covered by a 12-Month Warranty against functional failure under normal operating conditions. Prior to shipment, each unit undergoes a functional verification check to confirm power-up, parameter access, and I/O response. Units are packed in anti-static, shock-protected packaging suitable for international freight.

If a unit develops a fault within the warranty period, TOPNLMS provides replacement support with priority processing. Our technical team is available to assist with fault code diagnosis, parameter configuration questions, and compatibility verification before and after purchase. We maintain stock of 1391 Series drives to support urgent replacement needs, with same-day or next-business-day dispatch available for in-stock units.

For volume procurement, OEM integrators, and MRO purchasing teams, we offer quantity pricing, inspection reports on request, and consolidated shipping to reduce per-unit logistics cost. Contact our team to discuss your project requirements.