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Spindle Inverter Drive 3.7 kW – Fuji Electric FRN3. 7M5-2
The FRN3. 7M5-2 is a 3.7 kW CNC spindle inverter drive (“Spindle Inverter Drive”) from the FRENIC 5000MS5 series, manufactured by Fuji Electric. Designed specifically for variable-speed spindle control in CNC machine tools (vertical and horizontal machining centres, CNC lathes, milling machines), the drive converts three-phase mains voltage into variable-frequency, variable-voltage output to control spindle motor speed and torque. It incorporates features dedicated to machine tool requirements: spindle orientation for automatic tool change, C-axis mode, and DC braking. Available in multiple power ratings within the same MS5 family.
The FRENIC 5000MS5 spindle inverter drive is the electronic unit that converts three-phase mains power into variable frequency and voltage to govern spindle motor speed and torque throughout every phase of the machining cycle. It manages critical functions including spindle orientation for automatic tool changers, closed-loop control via encoder feedback, and rapid braking on stop. A failure of this unit renders the spindle completely uncontrollable, halting production and requiring immediate specialist intervention.
Fuji Electric Co., Ltd. is a Japanese industrial group founded in 1923 and one of the world’s leading manufacturers of industrial inverters, electric drives and automation systems. The FRENIC 5000MS5 series was dedicated specifically to the CNC machine tool industry and is today legacy / discontinued, superseded by newer lines such as FRENIC-Ace and FRENIC-MEGA; spares are available only as used units, surplus stock or through specialist repair services.
Main Technical Specifications
| Type | CNC spindle inverter drive (Spindle Inverter Drive) |
| Part number | FRN3. 7M5-2 (FRN37M52) |
| Brand | Fuji Electric |
| Series | FRENIC 5000MS5 |
| Known application | CNC machining centres, CNC lathes and milling machines with variable-speed spindle |
| Function | Spindle motor speed and torque control; spindle orientation; C-axis mode; DC braking |
| Rated output power | 3.7 kW |
| Input voltage | 3-phase 200–220 V AC, 50/60 Hz (200 V class) |
| Output frequency | 0–400 Hz (typical for spindle drives) |
| Output voltage | 0–200 V three-phase variable (PWM) |
| Feedback | Incremental encoder / tachogenerator from spindle motor |
| Interfaces / connectors | Multi-function control terminal strip; encoder connector; power terminals R/S/T – U/V/W |
| Weight | ~3–6 kg |
| Dimensions | ~200×300×150 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |
Variable Frequency Drive (Inverter) – FUJI FRN003M3-21
The FRN003M3-21 is a variable frequency drive / inverter (“Variable Frequency Drive” – VFD) belonging to the FRENIC family manufactured by FUJI Electric. The part number identifies a compact frequency converter in the ~0.3–0.4 kW power class, 200 V class, designed for the speed control of three-phase induction motors in industrial applications and CNC machine tools. The unit belongs to one of the historical compact FRENIC series produced by FUJI Electric from the 1990s onward for motion control applications across a wide range of manufacturing sectors.
The frequency inverter converts fixed-frequency mains power into a variable-frequency, variable-amplitude three-phase output, enabling continuous and precise speed regulation of the driven induction motor. In a CNC machine tool it can serve the low-power spindle drive, coolant pump, chip conveyor, or auxiliary axes. A failed inverter immediately halts the controlled function in an uncontrolled manner: without it the motor cannot start or vary its speed, rendering the served machine section completely inoperative.
FUJI Electric Co., Ltd. is a leading Japanese power electronics manufacturer, founded in 1923 as a joint venture between Furukawa Electric and Siemens. The FRENIC inverter family covers power ratings from a few watts to hundreds of kilowatts and is deployed worldwide in CNC, HVAC, and industrial automation applications. Models from the M3 series and contemporaneous variants are to be regarded as legacy / discontinued: available only as used, surplus, or through specialist repair.
Main Technical Specifications
| Type | Frequency inverter / Variable Frequency Drive (VFD) |
| Part number | FRN003M3-21 (FRN003M321) |
| Brand | FUJI Electric – FRENIC series |
| Known application | CNC machine tools; auxiliary motor control, low-power spindle, coolant pump, chip conveyor |
| Function | Three-phase AC induction motor speed control via PWM modulation (V/f and/or sensorless vector) |
| Rated power | ~0.3–0.4 kW |
| Input voltage | Three-phase 200–240 V AC, 50/60 Hz |
| Output voltage | Three-phase 0–240 V AC, PWM modulated |
| Output frequency | 0–400 Hz |
| Rated output current | ~2.5 A |
| Interfaces / connectors | Power terminal block R/S/T (input) – U/V/W (output); control connector for analogue reference (±10 V) and digital I/O |
| Weight | ~0.5–1.5 kg |
| Dimensions | ~100–180 mm (H) × 80–140 mm (W) × 80–120 mm (D) |
| Production status | Legacy / discontinued — used / surplus / repair only |
AC Spindle Drive – FUJI FMD-11AC-21A
The FMD-11AC-21A is an AC spindle drive (“AC Spindle Drive”) from the FRENIC 5000M2 series by Fuji Electric. Designed specifically for vector speed and torque control of AC spindle motors on CNC machine tools, it sits between the mains supply and the spindle motor, converting fixed mains voltage into variable voltage and frequency. The prefix FMD identifies the spindle drive family within the FRENIC 5000M2 series; the numeric designation encodes the power class (~11 kW), AC indicates alternating-current technology, and 21A specifies the voltage variant (200 V class) and hardware revision. The unit may exist in multiple revisions and variants; option modules such as serial communication boards, EMI filters and encoder interface cards were available as separate accessories.
The AC spindle drive is the electronic core of the spindle speed control system in the machine tool: it receives the speed reference from the CNC, closes the speed and torque loop via encoder or tachogenerator feedback, and supplies the motor with the power required to hold the programmed speed constant under varying cutting loads. Failure of this unit causes immediate spindle shutdown and total machine downtime: no machining is possible until the drive is replaced or repaired, with consequent production losses and risk of scrapped workpieces.
Fuji Electric is a Japanese industrial group founded in 1923 and a world leader in the design and manufacture of AC/DC drives, inverters and industrial automation systems for precision applications. The FRENIC 5000M2 series belongs to the generation of CNC machine-tool spindle drives from the 1990s–2000s and is now legacy / discontinued: spare units are available only as used, NOS surplus, or through specialist repair centres.
Main Technical Specifications
| Type | AC spindle drive – vector inverter (AC Spindle Drive) |
| Part number | FMD-11AC-21A (FMD11AC21A) |
| Brand | Fuji Electric |
| Series | FRENIC 5000M2 |
| Known application | CNC machine tools with AC spindle motor (vertical/horizontal machining centres, CNC lathes) |
| Function | Vector speed and torque control of AC spindle motor |
| Power class | ~11 kW |
| Input voltage | 3~ 200 V AC ±10%, 50/60 Hz – 200 V class |
| Output voltage | 3~ variable 0–200 V, variable frequency 0–400 Hz |
| Reference input | Analogue ±10 V / 0–10 V; serial RS-232 / RS-422 (optional) |
| Feedback | Incremental encoder / tachogenerator from spindle motor |
| Built-in protections | Overcurrent, overtemperature, undervoltage, overvoltage, earth fault |
| Interfaces / connectors | Power terminal block, edge signal connectors, optional serial port |
| Weight | ~8–15 kg |
| Dimensions | ~300–500 mm × 200–350 mm |
| Production status | Legacy / discontinued — used / surplus / repair only |
Positioning Control Board – FUJI EP-3358C-C
The EP-3358C-C is an electronic positioning control board (“Positioning Control Board”) manufactured by FUJI Electric, designed for use in CNC systems and industrial automation equipment of the same make. The board handles axis position control and feedback processing from encoders or resolvers, interfacing with the servo drives within the same control system. It is not a CPU or generic I/O module, but a dedicated unit for precise machine axis positioning.
The positioning board is the electronic module that closes the position loop in the CNC system: it processes axis encoder feedback signals, calculates position error, and generates correction references for the servo drives. Without it, precise axis positioning is impossible: any machining operation requiring tight geometric tolerances would produce out-of-tolerance parts or risk collisions due to position reference errors.
FUJI Electric is a Japanese manufacturer with over a century of history in industrial electronics, founded in 1923 as a joint venture between Furukawa Electric and Siemens. Specialised in power electronics, drives, CNC systems and factory automation (FA), its product lines include the FRENIC inverter series and Alpha servo systems. Products in the EP-3358C-C family belong to a legacy / discontinued generation of controls and are available only as used units, NOS stock, or through specialist repair services.
Main Technical Specifications
| Type | Positioning control board (Positioning Control Board) |
| Part number | EP-3358C-C (EP3358CC) |
| Brand | FUJI Electric (legacy) |
| Known application | FUJI Electric CNC systems and industrial automation equipment |
| Function | CNC axis positioning control and regulation |
| Feedback | Incremental encoder / resolver (typical FUJI systems) |
| Logic supply voltages | ±15 V and +5 V DC (typical FUJI control boards) |
| Interfaces | Edge / flat cable connectors towards CPU and servo drives |
| Axes managed | ~1–4 axes |
| Weight | ~0.3–0.8 kg |
| Dimensions | ~150–280 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |
Axis Positioning Control Board – FUJI EP-3308D-C
The EP-3308D-C is an electronic axis positioning control board (“Axis Positioning Control Board”) manufactured by FUJI Electric, belonging to the numerical control and industrial automation product family of the same manufacturer. The board processes position commands from the CNC CPU, compares them with axis encoder feedback signals, and calculates the speed reference to be transmitted to the drives. The series identifier EP-3308 designates the board family within FUJI’s positioning control range for this generation; the suffix identifies variant D and revision C.
The axis positioning board is the central element of motion control: it receives position commands from the CNC processor, compares them with the feedback signal (encoder or resolver), and calculates the following error to continuously correct the axis trajectory. Without this board, the CNC system loses complete control of the axes: any movement becomes uncontrolled, with consequent risk of collision, dimensional rejection of the workpiece, or serious mechanical damage to the machine.
FUJI Electric is a Japanese industrial group founded in 1923, with strong specialisation in power electronics, inverters, drives, CNC systems and industrial automation. Historically present in the machine tool market with proprietary axis control systems, the group has progressively oriented its offering towards new-generation integrated solutions. The CNC control modules and boards of this series are legacy / discontinued: available exclusively as used, surplus or through specialist repair.
Main Technical Specifications
| Type | Axis positioning control board (Axis Positioning Control Board) |
| Part number | EP-3308D-C (EP3308DC) |
| Brand | FUJI Electric |
| Known application | FUJI Electric CNC systems and industrial automation; machine tools with FUJI numerical control (machining centres, CNC lathes) |
| Function | Axis position loop closure; encoder/resolver signal processing; following error calculation; speed reference output to drives |
| Variant / Revision | Variant D – Revision C |
| Supported feedback | Incremental encoder / resolver (typical for FUJI systems of this generation) |
| Supply voltages | ±15 V and +5 V DC (typical for FUJI control boards) |
| Interfaces / Connectors | Backplane bus connectors, axis encoder inputs, drive outputs and axis I/O signals (typical for FUJI rack systems) |
| Weight | ~0.2–0.6 kg |
| Dimensions | ~150–280 mm |
| Production status | Legacy / discontinued — used/surplus/repair only |