Description:
The NDBU-85 (ABB article number 57520001-BR) is an ABB DDCS (Direct Data Communication System) Branching Unit / optical fiber hub used in ABB drive systems—including ACS600, ACS1000, ACS800 (certain multi-drive configs), and DCS500 DC drive lineups—to distribute the fiber-optic DDCS link from a master drive or control module to up to five slave nodes (other drives, I/O modules, or gate units). It converts a single DDCS transmit/receive pair from the master into five replicated optical ports, allowing a single drive controller to synchronize and exchange process data with multiple subordinate drives or expansion boards without signal degradation.h2 Application Scenarios:A steel rolling mill operates a 3-stand tandem mill where the main 4.16 kV ACS1000 master drive communicates via DDCS fiber link to three ACS600 auxiliary drives (pinch rolls, side guides) and a standalone SDCS-CON-2 control board in the same cubicle row. Originally daisy-chained, the link suffered intermittent CRC errors during high-current acceleration due to marginal optical budget. The retrofit installed an NDBU-85 branching unit powered from the cabinet’s 230 V AC service. The master’s DDCS fiber was patched to the NDBU-85 INPUT port; OUTPUT ports 1–4 were connected to the three ACS600 slaves and the CON-2 board (Port 5 left unused / terminated per manual). The star topology improved optical margin by eliminating mid-chain connectors and gave each slave a dedicated optical path. Post-installation, DDCS communication error counts dropped to zero across all drives even during full torque steps. The drive systems engineer commented that the NDBU-85 “turned a fragile daisy chain into a bulletproof star—five minutes to install, years of quiet operation.”h2
Parameter:
| Main Parameters | Value/Description |
|---|---|
| Product Model | NDBU-85 (ABB Spare Part No. 57520001-BR) |
| Manufacturer | ABB (Drives / Discrete Automation Division) |
| Product Category | DDCS (Direct Data Communication System) Branching Unit / Optical Fiber Hub |
| Number of Ports | 1 × Input (FROM Master / Controller) 5 × Output (TO Slaves / Expansion Boards) |
| Fiber Type / Wavelength | 1000 µm POF (Plastic Optical Fiber), 820 nm typical — mates with ABB HFBR / DDCS fiber connectors |
| Maximum Fiber Length (per port) | ≤ 30 m (recommended; max. per DDCS POF spec — verify against your installation) |
| Power Supply | 110–120 V AC or 220–240 V AC (selectable via internal link / voltage selector — verify label) |
| Power Consumption | < 5 W typical |
| Status Indication | PWR LED (green = supply OK), LINK / ACT per port (some versions show Input Activity only) |
| Isolation / Protection | Short-circuit & overload protected PSU; optical ports are inherently galvanically isolated |
| Mounting Method | 35 mm DIN rail (TS35) — typically in drive control cabinet near master drive |
| Operating Temperature | 0 °C to +55 °C |
| Housing / Protection | IP20 (terminal side); unit intended for installation inside enclosed cubicle |
| Dimensions (approx.) | 110 × 75 × 45 mm (H × W × D) |
| Key Note | Match article number 57520001-BR; earlier NDBU-01/02 exist with fewer ports — confirm your system needs 5-output NDBU-85 |
| Certifications | CE, cULus (per ABB drive-system component listing) |
h2 Technical Principles and Innovative Values:
- Innovation Point 1 — Star Topology DDCS Distribution with Regenerated Optical Signals. The NDBU-85 doesn’t merely split the optical power (which would weaken the signal 5-way); it receives the serialized DDCS telegram from the master, regenerates and buffers it electronically, then retransmits identical copies to each of the five output ports. This preserves the original optical signal quality and allows each slave to be connected with standard-length POF without exceeding the DDCS link budget—a critical advantage over passive T-couplers.
- Innovation Point 2 — Galvanic Isolation Inherent in Fiber Links with Centralized PSU Supervision. Because all DDCS links are plastic optical fiber, there is zero electrical connection between the master drive, the NDBU-85, and the slave drives—eliminating ground-loop induced noise in mixed-power installations (e.g., a DC drive and an AC drive sharing DDCS). The branching unit’s own power supply is short-circuit protected and monitored by the front-panel PWR LED; loss of supply is immediately visible during cabinet walkthroughs, unlike passive splitters that fail silently.
- Innovation Point 3 — Simplified Multi-Drive Commissioning & Reduced Cable Stress. By providing dedicated output ports, the NDBU-85 eliminates the need to daisy-chain multiple drives/modules on a single DDCS fiber loop—a practice that increases connector count in the signal path and makes fault isolation difficult (a bad connector in the middle of the chain breaks communication to all downstream nodes). With the NDBU-85, a faulty slave’s fiber can be unplugged without affecting the others, and spares verification is as simple as patching a known-good drive to an unused port.
