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AC Servo Drive – NIKKI DENSO NPSA-5NN-50
The NPSA-5NN-50 is an AC servo amplifier (“AC Servo Amplifier”) manufactured by NIKKI DENSO (????), a Japanese specialist in servo drive systems for CNC machine tools. The unit belongs to the NPSA series, designed for the control of linear and/or rotary axes on machining centres, CNC lathes, and grinding machines of Japanese manufacture from the 1980s and 1990s. It manages the current and speed control loops of the AC servo motor, interfacing with the CNC controller via an analogue reference signal and receiving feedback from the incremental encoder mounted on the motor. The suffix NN denotes the configuration variant and 50 the power/size code within the series.
The servo drive is the power module that converts CNC commands into current, torque, and velocity on the axis servo motor: it closes the control loop in real time, ensuring the positioning and interpolation accuracy required by machining. A drive failure renders the axis completely inoperative; the machine cannot execute controlled movements, causing immediate production stoppage and risk of collision if control is lost during motion.
NIKKI DENSO (????????) is a Japanese manufacturer historically active in the design of AC servo drives and power amplifiers for industrial automation and CNC machine tools. Products in the NPSA series are legacy / discontinued: no longer available new from the manufacturer, and sourced exclusively through the used market, industrial surplus, or specialist repair services.
Main Technical Specifications
| Type | AC servo amplifier (AC Servo Drive) |
| Part number | NPSA-5NN-50 (NPSA5NN50) |
| Brand | NIKKI DENSO (????) |
| Known application | Japanese-built CNC machine tools (machining centres, lathes, grinding machines) |
| Function | Power amplification and speed/current loop control for AC servo motor |
| Input voltage | ~200–230 V AC three-phase |
| Rated current | ~5 A |
| Rated power | ~0.5–1.5 kW |
| Feedback | Incremental encoder from AC servo motor |
| Interfaces | On-board connectors; analogue reference input; encoder connector; power terminal strip |
| Weight | ~2–5 kg |
| Dimensions | ~150–250 × 100–200 × 80–150 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |