Product Core Brief

• Model: NDBU-95
• Part Number: 63985341 (also cross-referenced as 64008366 for the same hardware)
• Brand: ABB
• Series: ABB DDCS distributed drive communication family
• Core Function: DDCS fiber optic branching unit that expands one master fiber link into up to nine slave channels, enabling star-topology communication for ABB drive systems.
• Product Type: DDCS Optical Branching Unit / Fiber Star Hub
• Key Specs: 1× Master + 9× Slave channels | POF plastic fiber | 24 V DC supply | DIN-rail mounting | Independent channel fault isolation
• Condition: New Original / New Surplus

Key Technical Specifications

• Part number: 63985341
• Model designation:
• Function: DDCS fiber optic branching unit
• Channel configuration: 1× Master input, 9× Slave outputs (CH0–CH8)
• Fiber type: 1 mm POF plastic optical fiber
• Communication rate: 1–4 MBd, set by hardware DIP switches
• Supply voltage: 24 V DC ±10%, typical current ~300 mA
• Mounting: 35 mm DIN rail
• Dimensions: Approx. 264 × 84 × 50 mm (H × W × D)
• Weight: Approx. 0.7 kg
• Protection class: IP20, control cabinet installation
• Operating temperature: 0 °C to +50 °C
• Compatible systems: DCS600 and DCS800 DC drive systems; exact firmware/topology should be confirmed against the original equipment documentation
• Status indication: Per-channel receive LEDs for communication monitoring
• Note: NDBU-95 is not the same as NDBU-95C; the two variants differ in channel count and hardware configuration and are not directly interchangeable.

 

Product Introduction (No Fluff)

The ABB NDBU-95, part number 63985341, is a DDCS fiber optic branching unit used to distribute drive communication signals in ABB multi-drive systems. It takes one master DDCS fiber link and expands it into up to nine independent slave channels, allowing a star topology instead of a simple daisy chain.

This module is commonly referenced in DCS600 and DCS800 DC drive applications, including rolling mill and paper machine drive systems. Its main advantage is fault isolation: if one slave drive loses power or develops a fiber fault, the remaining drives can continue communicating. The unit is powered by 24 V DC and uses 1 mm POF plastic optical fiber, not glass fiber.

Because NDBU-95 and NDBU-95C have different channel configurations, the exact model must be matched to the original installation before replacement.

 

QA & Testing SOP (Dynamic & Transparent)

DDCS branching units should be checked for both physical integrity and communication readiness:

1. Inbound authenticity check: Confirm ABB branding, NDBU-95 marking, part number 63985341, label condition, fiber ports, DIP switches, and housing finish. Units with mismatched labels or damaged ports are quarantined.
2. Mechanical inspection: Check DIN-rail latch, fiber connectors, power terminal, PCB condition, and signs of overheating, moisture, or physical damage.
3. Variant verification: Confirm the unit is NDBU-95 (9 slave channels), not NDBU-95C (5 channels). The two are not directly interchangeable.
4. Power-up check: Apply 24 V DC and verify power LED and basic status indicators.
5. Channel inspection: Visually inspect all fiber ports for contamination or damage; confirm per-channel LEDs respond when a known-good fiber link is connected.
6. Final packing: Units are shipped with fiber port protection, anti-static packaging, and moisture control.

 

Installation Pitfalls & Guide (Engineer to Engineer)

❗ Do not substitute NDBU-95 with NDBU-95C. NDBU-95 provides 9 slave channels, while NDBU-95C has a different channel configuration. Hardware and topology settings are not directly interchangeable.

❗ Use only POF plastic optical fiber. Glass fiber or incorrect fiber types may cause link failures or excessive attenuation.

❗ Verify DIP switch settings before commissioning. Communication rate and node settings must match the existing DDCS network. Incorrect settings can prevent drive recognition.

❗ Check star topology wiring. Each slave drive should connect to its own NDBU-95 slave channel. Miswiring can create communication loops or orphaned nodes.

❗ De-energize before wiring changes. Although fiber links are electrically isolated, power and control wiring should only be modified when the system is safely de-energized.

Replacement steps:

1. Pre-install: Record the original part number, DIP switch positions, fiber port assignments, and drive node mapping.
2. Removal: De-energize the 24 V DC supply, label fiber cables, and disconnect power and fiber links.
3. Install: Mount the NDBU-95 on the DIN rail, set DIP switches, reconnect fiber cables to the correct slave channels, and apply 24 V DC.
4. Commissioning test: Verify per-channel LEDs, confirm drive communication, and check that individual slave faults do not collapse the entire DDCS link.

 

Technical FAQ

1. What does the NDBU-95 do?
It is a DDCS fiber optic branching unit that expands one master fiber link into up to nine slave channels, enabling star-topology communication for ABB drive systems.

2. Is 63985341 the same as 64008366?
Yes. These part numbers have been referenced as cross-equivalent for the same NDBU-95 hardware.

3. Can NDBU-95 replace NDBU-95C?
No. NDBU-95 and NDBU-95C differ in channel count and hardware configuration and should not be treated as direct replacements without confirming system compatibility.

4. What fiber type does it require?
It requires 1 mm POF plastic optical fiber. Glass fiber is not supported.

5. Which drives is it compatible with?
It is referenced for DCS600 and DCS800 DC drive systems. Exact compatibility, firmware requirements, and topology limits should be confirmed against the original equipment documentation.