Siemens C98043-A7001-L24 CUD1 Control Board for SIMOREG 6RA70 DC Drives

The Siemens C98043-A7001-L24 is a CUD1 (Control Unit for DC Drives) electronic board designed for the SIMOREG 6RA70 series of DC converters. This board provides closed‑loop control for both armature and field circuits of industrial DC motors. The CUD1 executes the drive's control algorithms, including speed control, torque control, current limiting, and field weakening. It accepts analog and digital inputs from the motor and process, processes them through its firmware, and generates firing pulses for the thyristor power section. The board is equipped with an EPROM (or flash memory) containing the operating software. This particular variant (L24) corresponds to a specific software version and hardware revision.

Technical Specifications

• Model: C98043-A7001-L24

• Product Type: CUD1 (Control Unit for DC Drives)

• Compatible Drive Series: SIMOREG 6RA70 (DC converter)

• Primary Functions: Armature and field circuit closed‑loop control

• Control Modes: Speed control (with/without encoder), torque control, EMF control

• Field Control: Regulated field supply for shunt-wound motors (field weakening)

• Firmware Storage: EPROM / flash memory (software version > 3.0)

• Communication Interfaces: PROFIBUS DP (optional via CBP2), USS, RS‑485

• Analog Inputs: 2 (speed setpoint, auxiliary)

• Analog Outputs: 2 (actual speed, actual current)

• Digital Inputs: 6 (enable, reversing, fault reset, etc.)

• Digital Outputs: 4 (ready, running, fault, etc.)

• Power Supply: 24V DC (from drive's auxiliary power)

• Operating Temperature: 0°C to 45°C

• Dimensions: Standard Eurocard form factor

Functional Description

The CUD1 board is the intelligence behind the SIMOREG 6RA70 DC drive. It samples the armature current via internal current transformers, the armature voltage via voltage dividers, and the motor speed via an optional encoder or tachometer. The board's microcontroller executes a field‑oriented control algorithm, generating firing angles for the thyristor bridge. For field control, the CUD1 also controls the field converter, providing regulated field current to enable field weakening above base speed. The board includes a dedicated field regulator that maintains constant field current or implements weakening according to a pre‑programmed curve.

Firmware and Software Versions

The software version is indicated by the last character(s) in the C98043-A7001-Lxx numbering. The L24 variant corresponds to a firmware version later than 3.0 (as L1 and L2 indicate earlier versions). The firmware implements the drive's parameter structure, fault handling, and communication protocols. Updates require replacing the EPROM or re‑flashing the memory. The parameter set is stored in non‑volatile EEPROM on the board, retaining settings even when power is removed.

Communication and Fieldbus

The CUD1 board includes a PROFIBUS DP interface via an optional CBP2 (Communication Board PROFIBUS) module, which plugs into the board. It also supports USS protocol on the RS‑485 port, allowing communication with Siemens PLCs and HMIs. The analog and digital I/O can be configured for various functions: speed setpoint (0–10V, 4–20mA), actual speed output, fault relay, and ready signal.

Diagnostics and Status Indication

The CUD1 includes diagnostic LEDs: READY (green), RUN (green), FAULT (red), and optional communication status. In case of a drive fault (overcurrent, overspeed, field failure, etc.), the board stores a fault code that can be read via the operator panel or communication link. The board also has an internal watchdog timer that resets the processor in case of software lock‑up. A hardware watchdog independently monitors the firing pulse generation for safety.

Applications

The CUD1 board is used in SIMOREG 6RA70 drives that power industrial DC motors in applications such as paper machine winders/unwinders, extrusion lines, crane hoist drives, elevator motors, and test stands. The board is a common spare part for maintaining these legacy drives.

Installation and Replacement

The CUD1 board is mounted vertically inside the 6RA70 drive enclosure, attached to the drive's power chassis. To replace a faulty board, power down the drive, remove the front cover, disconnect ribbon cables (to the operator panel and I/O), and extract the board from its guide rails. Install the new board, ensuring all connectors are fully seated. After replacement, reload the motor parameters from a backup or re-enter them via the operator panel. The board is ESD‑sensitive; take appropriate precautions.

Conclusion

The Siemens C98043-A7001-L24 CUD1 control board provides the precise, real‑time closed‑loop control essential for SIMOREG 6RA70 DC drives, supporting industrial DC motor applications requiring high dynamic performance and reliability.