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AC Servo Drive – OKUMA BDU-15A
The BDU-15A is an AC servo drive unit (“AC Servo Drive Unit”) manufactured by OKUMA, belonging to the BDU (Brushless Drive Unit) series of integrated CNC axis drives. It is documented as a component of OKUMA CNC machining centres and turning centres equipped with the proprietary OSP (Open System Platform) control. The number 15 in the part number denotes the rated output current (15 A); the letter A identifies the construction variant. The unit manages the current and velocity loops of the servo axis motor, receiving position and velocity references from the CNC CPU via the proprietary OKUMA bus.
The BDU-15A is the electronic controller that converts trajectory commands from the CNC CPU into phase currents for the servo motor, closing the current and velocity loops in real time and ensuring rapid, precise axis positioning throughout machining cycles. If it fails, the controlled axis loses all movement capability: the machine triggers an alarm and stops immediately, making any productive operation impossible.
OKUMA Corporation is one of the world’s leading CNC machine tool manufacturers, founded in 1898 in Nagoya, Japan. It is the only manufacturer in the world that designs and produces machines, CNC controls (OSP), drives, and motors entirely in-house: a fully integrated, proprietary ecosystem. Components in the BDU series are legacy / discontinued: available only as used, surplus, or through specialist repair.
Main Technical Specifications
| Type | AC servo drive unit for CNC axis |
| Part number | BDU-15A (BDU15A) |
| Brand | OKUMA Corporation |
| Known application | OKUMA CNC machining centres and turning centres with OSP (Open System Platform) control |
| Function | Axis servo motor current and velocity regulation; current and velocity loop closure |
| Rated output current | 15 A |
| Supply voltage | 3-phase 200–230 V AC, 50/60 Hz |
| DC bus voltage | ~280–320 V DC |
| Feedback | Incremental encoder / resolver from servo axis motor |
| Interfaces / connectors | Proprietary OKUMA serial bus (OSP); multiple connectors for encoder, motor power and I/O |
| Built-in protections | Over-current, over-temperature, DC bus over-voltage, output short-circuit |
| Weight | ~1.5–3.5 kg |
| Dimensions | ~150–250 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |