ABB 3ASU21C110​ DCU30/7 Desk Control Unit: 4 Digital Inputs, 3 Digital Outputs, Backlit LCD for AC Drive & Pump/Fan Control Rooms

Description

Technical Specifications

Main Features and Advantages

Operator-first HMI for drive control desks.​ The 3ASU21C110​ exists because paper-machine drive sections and VSD control rooms still rely on physical desk positions where a lead operator needs local start/stop, speed trim, and fault-reset at hand height — not buried three menu layers deep in a PC-based SCADA. The backlit LCD on the 3ASU21C110​ shows speed, current, fault codes, and status words in real time, while the pushbutton array lets the operator navigate parameters, change speed reference, or acknowledge alarms without a laptop or a handheld communicator. For night-shift troubleshooting on a paper-machine drive floor, that local visibility is the difference between a five-minute reset and a two-hour hunt through MasterFieldbus diagnostics.4 DI / 3 DO built onto the desk unit.​ Although the 3ASU21C110​ is primarily an HMI, the embedded digital I/O means the desk itself can host simple local logic — e.g., a desk-mounted “Emergency Stop” mushroom wired to one of the 4 DIs, or a “Run Permission” feedback from a local guard switch, with the 3 DOs driving desk-side indication lamps or a small siren. This keeps trivial I/O off the drive’s main terminal strip and lets the desk function semi-autonomously if the upstream link glitches. For retrofits replacing DCU20, the DI/DO count is identical, so existing desk-side wiring lands without re-termination.Dual-protocol RS485: MasterFieldbus + Modbus RTU.​ ABB’s MasterFieldbus is the native serial multidrop used in paper-machine drive coordination (DCS ↔ drive sections ↔ desk units), and the 3ASU21C110​ speaks it natively — plug into the existing bus trunk alongside other DCU30/7 panels and DCS nodes, and the desk auto-enumerates. For non-ABB or mixed-brand plants, the same RS485 port also carries Modbus RTU, letting the 3ASU21C110​ land on a third-party PLC/SCADA as a generic HMI node. That dual-stack is unusual for a desk-unit this age and explains why the 3ASU21C110​ still finds work in brownfield modernization where the drive layer stays ABB but the DCS is migrating.0–10 V analog reference input.​ The 3ASU21C110​ accepts an external 0–10 V command — useful when the desk sits next to a manual potentiometer, a PLC analog output, or a process-variable transducer (flow/pressure) that the operator wants to “hand off” to the drive as speed reference. The analog path is separate from the digital comms, so even if MasterFieldbus is down for maintenance, the desk can still shove a manual speed ref into the drive (depending on drive-parameter configuration).Drop-in upgrade from DCU20.​ The DCU20 was the previous-generation ABB desk unit; connector pinout is identical between DCU20 and DCU30, but the DCU30/7 housing is slightly smaller. ABB supplies a conversion plate so the 3ASU21C110​ fits the DCU20 cutout without re-machining the desk — a 15-minute swap instead of a carpenter visit. For plants with ten DCU20 desks along a paper-machine drive aisle, standardizing spares on the 3ASU21C110​ simplifies the shelf even while old DCU20s linger.IP65 front, industrial build.​ The operator-facing bezel on the 3ASU21C110​ is IP65 — coffee spills, cleaning sprays, and paper-dust don’t kill the LCD or the pushbutton membrane. The rear (desk-interior side) isn’t IP65, but that’s fine since it lives inside the desk cavity. At 3.3 kg the unit feels substantial — zinc/aluminum alloy front frame, not plastic — which matters in a paper-mill environment where a hollow plastic bezel would get cracked by the first toolbox bump.