CONTROL TECHNIQUES Servo Drive

---

AC Variable Speed Drive – CONTROL TECHNIQUES SP1404

The SP1404 is an electronic AC variable speed drive (“AC Variable Speed Drive / Inverter”) by Control Techniques, part of the Unidrive SP series. Designed for control of three-phase induction motors and permanent magnet motors, it supports open-loop vector (RFC-A), closed-loop vector with encoder feedback, and servo control modes. Nominal input voltage 380–480 V AC three-phase 50/60 Hz; nominal output current approximately 14 A continuous; power class 5.5–7.5 kW at 400 V. Features an onboard PLC, digital and analogue I/O, RS485 serial interface, and expansion slots for optional fieldbus modules.

The AC variable speed drive is the power electronic converter that transforms fixed-frequency mains supply into variable voltage and frequency to regulate motor speed and torque. In CNC machine tools it controls the spindle, feed axes, or auxiliary motors, ensuring precise and continuous regulation across the full operating range. A drive failure results in the immediate loss of control of the affected axis or spindle, halting the machine and preventing resumption of machining.

Control Techniques is a British manufacturer of variable speed drives and servo systems, founded in 1973 and headquartered in Newtown, Wales. Acquired by Emerson Electric in 1992 and subsequently by Nidec Corporation in 2017, it now operates as Nidec Control Techniques. The Unidrive SP series is legacy / discontinued in its original variants, progressively replaced by the Unidrive M series: spare units are available primarily as used stock, NOS surplus, or through specialist repair services.

Main Technical Specifications