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AC Variable Speed Drive – CONTROL TECHNIQUES UNI2403

The UNI2403 is an AC variable speed drive (“Variable Speed Drive”) from the Unidrive Classic family, manufactured by Control Techniques. Documented on CNC machining centres, milling machines and lathes equipped with three-phase induction motors, it regulates motor speed and torque via PWM modulation. It operates in open-loop V/Hz, open-loop vector (sensorless) and closed-loop vector modes with encoder feedback. The Unidrive Classic is the first generation of the Unidrive platform, predecessor to the Unidrive SP and Unidrive M families.

The variable frequency drive is the power and regulation element that converts three-phase mains voltage into variable voltage and frequency, enabling precise speed and torque control of the induction motor. A drive failure completely disables the associated axis or spindle, bringing the machine to a standstill; typical faults include overvoltage, overtemperature, loss of encoder feedback or short-circuit on the IGBT power stage.

Control Techniques is a British manufacturer founded in 1973, specialising in AC and DC drives, servo systems and industrial motors. Acquired by Emerson Electric in 1994 and subsequently by Nidec Corporation in 2012, it now operates as the Nidec Control Techniques division. The Unidrive Classic line is legacy / discontinued: available only as used, NOS or through specialist repair.

Main Technical Specifications

AC Vector Inverter / Variable Speed Drive – Control Techniques SP2402

The SP2402 is an AC variable speed drive (“AC Inverter / Variable Frequency Drive”) from the Unidrive SP series, manufactured by Control Techniques. It belongs to the Frame 2, 400 V class and is employed on CNC machine tools and industrial automation systems requiring precise speed and torque control of AC induction or permanent-magnet synchronous motors. It supports four operating modes: scalar V/Hz, Open Loop Vector (sensorless), Closed Loop Vector (with encoder), and Servo. An integrated RS485 / Modbus RTU interface and an option slot for fieldbus expansion modules (Profibus-DP, CANopen, DeviceNet, EtherCAT) are included.

The inverter converts the fixed-frequency mains supply into a variable-voltage, variable-frequency three-phase output, enabling precise control of motor speed and torque. In a CNC machining centre, a drive failure causes immediate shutdown of the controlled axis or spindle: the machine stops, the workpiece risks being scrapped, and — should active safety not intervene — a collision may occur.

Control Techniques is a British manufacturer founded in 1968 and specialised in variable-speed drives for AC and DC motors. Acquired by Emerson Electric in 1992 and later by Nidec Corporation in 2017, it now operates as Nidec Industrial Solutions. The Unidrive SP series is legacy / discontinued: the platform has been superseded by the Unidrive M family; SP drives are available exclusively as used, NOS (surplus), or through specialist repair centres.

Main Technical Specifications

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

DC Motor Drive – Control Techniques DB 420 NP

The DB 420 NP is a DC motor drive (“DC Motor Drive”) manufactured by Control Techniques, belonging to the DB series of the Welsh manufacturer’s industrial drive range. The part number identifies a combined control and power unit for DC motors intended for industrial motion control applications; the NP designation denotes a specific constructional variant (typically “Non-Plug-in” or a configuration without a removable optional module). The drive manages the speed and torque regulation loops, interfacing with the CNC system’s control bus and with the motor’s tachogenerator or encoder feedback. The product is documented on CNC machine tools, automated production lines and numerical control systems using DC motors for axis or spindle drives.

The DC drive is the core of the motor control system: it receives the speed or torque reference from the numerical controller, regulates voltage and current to the motor armature and closes the feedback loop to deliver the required motion profile with precision and stability. A drive failure renders the controlled motor completely unmanageable, causing immediate process stoppage and a real risk of mechanical damage to moving parts; availability of a replacement unit is therefore critical to limiting unplanned machine downtime.

Control Techniques, founded in 1961 in Newtown (Wales, UK), is one of the world’s leading manufacturers of variable-speed drives for AC and DC motors, servo drives and motion control systems (Mentor, Unidrive, Commander, Digitax, Epsilon families). Acquired by Emerson Electric in 1992 and subsequently by Nidec Corporation in 2017, it continues to operate as an independent brand within the group. Products in the DB series are legacy / discontinued: available only as used, surplus or through specialist repair.

Main Technical Specifications