Description

The 1391-DES45-DI-AQB-A​ is a digital AC servo drive from Allen-Bradley, part of the Bulletin 1391 family of single-axis motion controllers built for closed-loop speed and torque control. It is a full-size servo amplifier rather than a plug-in module, intended for cabinet mounting alongside its dedicated isolation transformer.The 1391-DES45-DI-AQB-A​ rectifies a three-phase 230 V AC supply into a 300 V DC bus and delivers 45 A RMS continuous and 90 A RMS peak to an AC servomotor, with speed held to within 0.05 % across a 95 % load change. The trailing -A suffix specifies a 24 V DC contactor coil, which is a detail that decides whether a replacement unit energises at all.

Application Scenarios

A packaging line built around an IMC S-class controller has been running for twenty years. One axis drives the film feed, and it has to accelerate, settle, and hold registration thousands of times per shift. The machine builder chose an Allen-Bradley 1326 servomotor with a matching drive, and the line still hits its original cycle time.The drive behind that axis is the 1391-DES45-DI-AQB-A. It takes a ±10 V DC speed command from the motion controller, reads rotor position back from the motor resolver, and closes the current loop in hardware at a 2500 Hz modulation rate. When the resolver cable is disturbed during a bearing change, the drive reports a fault on its integral display instead of running away, and the maintenance team reads the code off the two-line LCD rather than connecting a laptop in a cramped cabinet.What makes this matter commercially is the alternative. Replacing one axis of that machine means new drive, new motor, new feedback cabling, and a rewritten motion program, with validation time that usually exceeds the hardware cost by a wide margin. Keeping a 1391-DES45-DI-AQB-A​ on the shelf keeps the original architecture intact, and the line keeps its proven cycle time.

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