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Brushless Servo Drive – OKUMA BLII-D50A
The BLII-D50A is a brushless servo drive amplifier (“Brushless Servo Drive Amplifier”) manufactured by OKUMA, part of the BL II (Brushless II) family designed for OKUMA CNC systems with OSP control. The D50A designation indicates a continuous output current class of 50 A, sized for controlling linear and/or rotary axis servo motors on OKUMA machining centres and turning centres. The unit interfaces the power stage with the CNC via OKUMA’s proprietary serial bus and acquires encoder feedback from the brushless axis motor.
The brushless servo drive is the power conversion and regulation unit that governs each machine axis motor: it receives position and speed references from the CNC, converts them into precise three-phase current for the brushless motor, and closes the position, speed, and current control loops. A drive failure renders the affected axis completely inoperable, triggers alarms that halt the entire machine, and prevents any machining until the unit is replaced or repaired.
OKUMA Corporation is one of Japan’s leading CNC machine tool manufacturers, founded in 1898 and listed on the Tokyo Stock Exchange (TSE). The company is renowned for its “One Source” philosophy: it independently designs and manufactures CNC controls (OSP series), motors, drives, and machine tools, ensuring full integration between all system components. Products in the BL II family are legacy / discontinued in the current catalogue: available mainly as used, surplus, or through specialist repair.
Main Technical Specifications
| Type | Brushless servo drive amplifier (Brushless Servo Drive Amplifier) |
| Part number | BLII-D50A (BLIID50A) |
| Brand | OKUMA Corporation |
| Known application | OKUMA CNC machining centres and turning centres with OSP control (e.g. MB, MU, LB, MA series) |
| Function | Position, speed, and current control of brushless axis servo motor |
| Rated output current | ~50 A continuous (from D50A designation) |
| Input voltage | 200–240 V AC three-phase, 50/60 Hz |
| CNC interface | OKUMA proprietary serial bus / board connectors and terminal strip |
| Feedback | Incremental / absolute encoder from OKUMA servo motor |
| Logic supply voltages | ±15 V and +5 V DC (typical, from centralised PSU) |
| Weight | ~3–7 kg |
| Dimensions | ~250–400 × 150–220 × 80–130 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |