Product Description:

The RAC 2.3-250-460-A0I-W1 is manufactured by Bosch Rexroth Indramat and is part of the RAC Spindle Drive Controllers series. Classified as an AC main spindle drive controller, it converts fixed plant power into variable, high-current output so that milling and turning spindles can follow programmed speed profiles. By modulating voltage and frequency in closed-loop response to machine commands, the unit supports precise cutting forces and consistent surface finishes in automated machining cells. In machining service, that control helps the spindle maintain commanded speed as cutting loads change across the tool path.

This controller is supplied without additional bleeder resistors, so external braking hardware must dissipate regenerated energy during rapid deceleration. Thermal management is handled by a built-in fan, with internal blower cooling allowing installation in cabinets where forced-air exchange is preferred over liquid systems. The mains terminals accept 3 x AC 400 V, 50 Hz, ±15%, or 3 x AC 460 V, covering common European and North American plant voltages without tap changes. Under those conditions, the power section can deliver a continuous output of 250 A, enough for large-frame induction or synchronous spindles that draw high startup currents. Speed reference arrives as an analog setpoint, and the control board interprets an analog (±10 V) signal for integration with legacy CNCs that generate differential voltage commands. This arrangement supports control systems that still use voltage-based speed commands instead of digital network references.

Field wiring lands on connector X4, 9 poles, providing a compact path for digital I/O and power supply leads to the logic circuitry. For position feedback distribution, the drive offers a buffered incremental encoder output, allowing downstream axis controllers or recorders to share the real-time spindle pulse train. The buffered signal can be used by external monitoring equipment without interrupting the primary feedback path. The unit operates without an additional encoder input, so any redundant feedback must be handled upstream. The unit is Version 3, which uses series-2 control algorithms for improved current linearity at low speeds.