Product Description:

The RAC 2.2-250-460-L00-Z1 is an AC main spindle drive controller produced by Bosch Rexroth Indramat for the RAC Spindle Drive Controllers series. It converts digital speed references from a CNC or motion PLC into regulated three-phase power for machine-tool spindle motors. By controlling both motoring and regenerative operation, the unit supports the torque, braking response, and speed stability needed in turning, milling, and grinding applications. The controller continuously adjusts motor current and voltage so the spindle can maintain commanded speed as cutting load changes. It is commonly used where spindle speed must remain stable across varying chip loads.

The controller can deliver up to 250 A of continuous output, which supports large spindle motors that require high current at low speed. That operating range gives the power stage enough capacity for demanding spindle duty during heavy cuts. It can be connected directly to mains up to 3 x AC 460 V, which can simplify installation where that supply is already available. Command and diagnostic data are exchanged through the SERCOS interface over fiber optics, and those fibers terminate at the X4 optical waveguide connection to help isolate control electronics from switching noise. Fiber-optic communication also helps preserve signal quality in cabinets that contain fast-switching power devices. Heat from the power section is removed by an internal blower that moves cabinet air across the heat sink during sustained operation.

A dedicated resistor bank serves as an additional bleeder, absorbing regenerated energy during deceleration so the DC bus stays within its permitted range. This is useful on spindles that return energy to the drive during rapid speed changes. The drive is supplied without an additional encoder input, which reduces wiring when one motor feedback device is sufficient for the application. The unit is Version 2, and it is intended for closed-loop spindle service rather than separate axis-position feedback tasks.