Product Description:

The RAC 2.3-250-380-API-W1 is a spindle drive controller manufactured by Bosch Rexroth Indramat within the RAC Spindle Drive Controllers series. Installed in milling machines, lathes, and grinding centers, it forms the link between the facility's CNC and the induction or synchronous main spindle. The controller converts command values into regulated three-phase power so that cutting speed and torque remain consistent during varying load conditions. This supports stable spindle behavior during acceleration, steady cutting, and rapid speed changes between machining steps.

The unit connects to plant power at 3 x AC 400 V and operates over the 50-60 Hz utility range. It supplies up to 250 A of output current, allowing high-inertia spindles to accelerate quickly without current derating. Heat generated by the power electronics is extracted by an internal blower, so the built-in fan removes the need for external ducting and helps keep the cabinet layout straightforward. Speed references are accepted as an analog (±10 V) command, enabling direct coupling to common motion controllers that deliver differential velocity setpoints. For panel wiring, all low-level signals are landed on the X4 9-pole terminal, which groups encoder, enable, and fault lines into one connector.

Tightly coordinated motion is supported by an integrated incremental encoder output that feeds real-time spindle position back to the CNC for threading or rigid tapping cycles. A separate additional encoder input for spindle feedback allows the drive to close its velocity loop around an external sensor when higher accuracy is required. Internally, signals are interpolated by a high-resolution INDRAMAT encoder, giving fine speed granularity across the full operating range. The drive operates without an additional bleeder resistor, so regenerated energy during deceleration is managed through the inverter's DC-bus allocation rather than a dedicated resistor. This keeps the enclosure compact while accommodating typical braking profiles.