ABB NDCU-21C
ABB NDCU-21C - Image 2

ABB NDCU-21C

Product Brief:​ The NDCU-21C is the inverter-side control unit​ used in ABB ACS800 / ACSM1 drives — particularly in multi-drive (common DC link) configurations where it acts as a DDCS slave receiving speed/torque reference from a master RDCU or PLC via DDCS fiber link. In single-drive applications the NDCU-21C functions equivalently to the RDCU (minus some master functions) — it runs DTC motor control, interfaces to the AINT gate-driver board, and provides local I/O (start/stop, DI/AI via NIOC piggyback). It is the “C” revision of NDCU-21 (improved EMC, conformal coat option). The unit includes the same DSP/DTC engine as the RDCU but lacks certain master-network capabilities (no direct fieldbus unless RDCO option added — though in slave mode fieldbus is on master).

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Category: SKU: ABB NDCU-21C

Description

ABB NDCU-21C

  • Technical Specifications (similar to RDCU but DDCS slave-focused):
    • Processor / Algorithm: Same DTC engine as RDCU-12C — 25 µs flux/torque estimation cycle
    • DDCS Interface: 1 × DDCS IN (fiber from master / NDBU-95), 1 × DDCS OUT (daisy-chain / unused); ST connectors
    • Local I/O: Via NIOC (NIOC-01 / NIOC-02) piggyback — 6 DI, 2 DO, 2 AI (with NAIO-03), 2 AO (with NAIO-03)
    • Motor Control: Induction, PMSM (with option), synchronous — 2 motor sets selectable
    • Power: 24 V DC from internal SMPS (derived from drive 230 V ACcontrol supply or external 24 V DC)
    • Indicators: Run, Fault, Ready LEDs on drive door; internal test LEDs on NDCU
    • Firmware: ACS800 drive firmware (same family as RDCU — must match power stack type)
    • Operating Temp.: –20 °C to +60 °C
    • Mounting: Inside inverter module on DIN rail / standoffs; connects to AINT gate-driver board via 40-pin ribbon + fiber
  • Functional Features:
    • Receives speed/torque setpoint, run/stop, direction from DDCS master (another ACS800 RDCU, or a DDCS master PLC/gateway)
    • Executes DTC motor control, monitors motor currents via AINT, protects on overcurrent/earth fault/overload
    • Can operate stand-alone (with local start/stop via NIOC) if DDCS master not used — jumper-configurable to “Single Drive” mode ignoring DDCS
    • Supports motor ID run (static/rotating) — must be initiated locally or via DDCS if master allows
  • Application Scenarios:
    • Slave inverter in common-DC-link multi-drive (paper machine sections, printing press towers, textile lines)
    • Retrofit replacement of faulty control unit in ACS800 inverter module
    • Stand-alone inverter with local control panel (keypad GOP / ACS-CP-D) — NDCU-21C + NIOC + NAIO-03 + RDCO (for keypad only, no fieldbus)
  • Material & Structure / Working Principle / Installation / Precautions:
    • In multi-drive: set DDCS node address via DIP switches on NDCU-21C or on AINT board (address 1–15); ensure unique addresses
    • Connect DDCS IN fiber from master/NDBU-95; verify Link LED illuminates
    • After replacement: download matching firmware via DriveWindow or USB if version mismatch indicated; perform motor ID if motor parameters lost
    • Precaution:​ NDCU-21C is ESD-sensitive — handle with wrist strap. Firmware must be compatible with power stack (frame size & type — inverter vs frequency converter vs DC choke unit). If used in single-drive mode, ensure parameter 51.01 (Module Type) is set correctly and DDCS ignore jumper is set if no master present.

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