Application Scenarios
A machine tool integrator was retrofitting a CNC grinding machine that required sub-micron positioning accuracy on the workpiece feed axis. The original analog servo drive drifted with temperature changes in the shop, causing gradual dimensional errors that only appeared after several hours of operation. The maintenance team replaced it with the 1398-DDM-075, which uses a microprocessor to close all control loops in the digital domain. Because the drive’s velocity and position regulators operate on numerical values rather than analog voltages, the thermal drift that plagued the original system disappeared entirely.
The practical value became obvious during a production run of precision bearing races: the 1398-DDM-075 maintained position repeatability throughout a 12-hour shift without needing mid-shift recalibration. The shop foreman noted that the drive’s built-in position window and in-position discrete outputs allowed the machine‘s PLC to confirm axis completion without polling, simplifying the control logic.
3. Parameter
| Parameter | Value / Description |
|---|---|
| Product Model | 1398-DDM-075 |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Category | Digital Servo Drive (Positioning) |
| Series | Ultra 200 / Bulletin 1398 |
| AC Input Voltage | 100–240 VAC, single-phase or three-phase |
| AC Input Frequency | 47–63 Hz |
| Continuous Output Current | 15 A (single-phase); 35 A (three-phase) |
| Peak Output Current | 50 A (single-phase); 75 A (three-phase) |
| Continuous Output Power | 7.5 kW at 240 VAC (three-phase) |
| Peak Power Output | 14 kW (single-phase); 20 kW (three-phase) at 240 VAC |
| DC Bus Voltage | 141–339 VDC |
| Control Modes | Torque, Velocity, Position (closed-loop digital) |
| Feedback Interface | Resolver, incremental encoder, or absolute encoder |
| Communication | RS-232/RS-485 serial; SERCOS fiber-optic ring (select models) |
| Discrete I/O | 5 opto-isolated inputs; programmable discrete outputs |
| Analog I/O | 2 inputs (0–10 V, 10-bit); 2 outputs (±10 V) |
| Operating Temperature | 0°C to +55°C |
| Cooling | Forced air (dual fans) |
| Mounting | Panel mount, IP20 enclosure required |
| Weight | Approximately 9.98–11.34 kg |
4. Technical Principles and Innovative Values
- Full Digital Control Loop: The 1398-DDM-075 replaces the analog compensation networks of earlier servo drives with a microprocessor that executes all current, velocity, and position loops numerically. This eliminates drift from component aging and temperature variation—a persistent problem in analog drives used in non-climate-controlled environments .
- Single or Three-Phase Input Flexibility: Unlike many servo drives that mandate three-phase power, the 1398-DDM-075 accepts single-phase input without external transformers. Field engineers can commission the drive on available single-phase supply for setup and testing, then switch to three-phase for full-power production once the electrical infrastructure is ready .
- SERCOS Fiber-Optic Multi-Axis Capability: Select 1398-DDM-075 configurations include a SERCOS interface that allows a single motion controller to coordinate up to 32 drives over a fiber-optic ring. Synchronization accuracy is in the microsecond range, enabling multi-axis interpolation for applications like CNC contouring and electronic line-shafting .
- Local Indexing Function (X Models): The “-075X” variant of the 1398-DDM-075 embeds positioning sequences—homing, relative moves, absolute moves—directly in the drive. The host controller can trigger an index and then attend to other tasks, reducing controller scan-time burden in multi-axis systems .
- Configurable Discrete I/O Matrix: The drive provides five selectable circuit inputs and programmable discrete outputs (in-position, at-speed, zero-speed, fault indications, etc.) that can be wired directly to a PLC or relay panel. This eliminates the need for a separate motion interface module in many applications .
