The MR-J2S-350A is Mitsubishi Electric’s 3.5 kW MELSERVO-J2 Super series servo amplifier for 200 V single-phase or three-phase AC power supply with pulse train position command input — a legacy servo amplifier from Mitsubishi’s second-generation MELSERVO Super platform, providing 3.5 kW continuous servo control at 17 A for HC-SFS352 and HC-RFS353 series servo motors in J2S-based servo systems requiring direct maintenance replacement without platform migration. Atlantech Drives holds stock of the MR-J2S-350A. Contact us for fast worldwide delivery and competitive pricing.
What Is the MR-J2S-350A?
The MR-J2S-350A is a MELSERVO-J2 Super series servo amplifier providing 3.5 kW (3,500 W) continuous output power for Mitsubishi HC-SFS352, HC-RFS353, and equivalent 3.5 kW servo motors with the J2S-era serial encoder. At 17 A continuous output current and 51 A peak (3×), the MR-J2S-350A fills the gap between 2 kW and 5 kW in the MR-J2S-A series — addressing heavier axis loads than the MR-J2S-200A can handle while avoiding the larger housing and higher power supply requirements of the MR-J2S-500A. The J2S-era 3.5 kW class was commonly specified for the primary feed axes of large-format CNC machining centres, the base rotation axes of medium-payload industrial robots, and the primary gantry axes of large-format cutting and processing machines built during the MR-J2S platform era. The MR-J2S-350A accepts position command pulses via differential RS-422A or open-collector input, implements the J2S three-loop servo control architecture, and communicates with the legacy MR Configurator software via RS-232C. Like all MR-J2S-A amplifiers, the MR-J2S-350A includes no built-in STO safety function and is appropriate only as a direct maintenance replacement.
Key Technical Specifications
- Model: MR-J2S-350A
- Rated Output Power: 3.5 kW (3,500 W)
- Power Supply: 200–240 VAC single-phase or three-phase, 50/60 Hz
- Continuous Output Current: 17.0 A
- Maximum Output Current: 51.0 A (3× continuous peak)
- Compatible Servo Motors: HC-SFS352, HC-RFS353 (J2S/J3-era motors)
- Command Interface: Pulse train input (open-collector or differential)
- Maximum Input Pulse Frequency: 500 kpps (differential), 200 kpps (open-collector)
- Encoder Interface: Serial encoder (J2S-era HC motor encoder protocol)
- Safety Function: None built-in
- Regenerative Brake: Built-in, external regenerative resistor connectable
- Communication: RS-232C (MR Configurator legacy software)
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 85 mm × 190 mm × 180 mm
- Weight: Approx. 2.5 kg
Typical Industrial Applications
The MR-J2S-350A is found in active service in heavy-duty servo axis applications from the MELSERVO-J2 Super era. In large-format CNC horizontal boring and milling machines, the MR-J2S-350A drives the X and Y axis saddle drives where the combined saddle mass and cutting force reaction demands 3.5 kW of sustained servo power at the machine’s programmed feed rates. Medium-payload industrial robots (30–60 kg payload) from the J2S era use the MR-J2S-350A for the primary trunk rotation and elevation axes, where the robot’s arm-plus-payload inertia requires 3.5 kW at rated acceleration and speed. In large-format waterjet and plasma cutting machines built during the J2S era, the MR-J2S-350A drives the primary gantry traverse axis where the beam structure mass and cutting head weight demand sustained 3.5 kW at the programmed traverse speeds. Press brake backstop positioning systems with servo backstop masses of 30–60 kg use the MR-J2S-350A for the backstop axis drive, providing the rapid positioning speed and sustained thrust required for multi-bend production cycles. The MR-J2S-350A is also found in extruder haul-off drives and tension control winding systems from the J2S era, where 3.5 kW in torque control mode provides the regulated torque required for consistent product tension during continuous web or profile production. In currently active service, MR-J2S-350A maintenance replacement requests typically arise from machines in automotive component manufacturing, sheet metal fabrication, and composite material processing where the machine’s mechanical systems remain viable but individual amplifier failures require parts that are no longer in standard distribution channels.
Replacement & Upgrade Notes
The MR-J2S-350A upgrade to current Mitsubishi servo technology follows the same two-component mandatory replacement approach as all MR-J2S models — the amplifier (MR-J2S-350A → MR-J4-350A) and the servo motor (HC-SFS352 → HG-SR352) must both be replaced simultaneously, as the J2S encoder protocol in the HC motor is not readable by any MR-J4 amplifier. Additional changes required for a complete J2S-350A-to-J4-350A upgrade include: new encoder cable (J2S and J4 encoder connectors differ in type and pinout), new motor power cable if the connector type has changed at the motor end, and complete servo parameter setup and auto-tuning from scratch using MR Configurator2. The MR-J4-350A provides the same 3.5 kW power with 22-bit encoder resolution (versus J2S base resolution), built-in dual-channel STO safety function, AVSC II dual notch filter, 0.888 ms or 0.444 ms SSCNET III/H command cycle (for the B variant), and MR Configurator2 USB commissioning interface. For facilities planning J2S-350A fleet migration, the total project scope per axis includes parts (amplifier + motor + cables), servo commissioning time (typically 4–8 hours per axis for gain tuning and acceptance testing), and production downtime during the mechanical and electrical changeover — plan the total project scope per axis before committing to the migration schedule. As an interim measure for machines where the MR-J2S-350A has failed but a J2S replacement cannot be sourced and a complete J2S-to-J4 upgrade cannot be executed immediately, Mitsubishi authorised service centres may offer MR-J2S-350A unit refurbishment (capacitor replacement, fan replacement, cleaning, functional test) as a temporary option to extend the service life of an existing working unit until the full upgrade can be scheduled.
Frequently Asked Questions
Q: Can the MR-J2S-350A be connected to a QD75MH4 MELSEC-Q positioning module for pulse train control?
A: Yes. The QD75MH4 positioning module generates differential RS-422A pulse output at up to 4 Mpps, and the MR-J2S-350A accepts differential pulse input at up to 500 kpps. The QD75MH4 pulse output is compatible with the MR-J2S-350A’s differential input — configure the QD75MH4’s maximum output pulse rate to 500 kpps or below to remain within the MR-J2S-350A’s rated input frequency. The QD75MH4’s 4 Mpps maximum output capability is not a problem — simply configure the commanded pulse rate within the MR-J2S-350A’s input limit.
Q: What size external regenerative resistor is recommended for the MR-J2S-350A driving a large horizontal machining centre feed axis?
A: For a 3.5 kW feed axis with frequent rapid deceleration cycles typical of CNC machining centre operation (10–20 decelerations per minute from rapid traverse speed), calculate the average regenerative power using the axis inertia, deceleration rate, and cycle frequency. For most horizontal machining centre feed axes at 3.5 kW with normal duty cycles, the MR-J2S-350A’s built-in regenerative resistor (approximately 20–30 W continuous capacity) is insufficient — an external MR-RB resistor of at least 100 W continuous rating (MR-RB14 or equivalent J2S-compatible external resistor) is typically required. Verify the specific external resistor resistance and power rating in the MR-J2S-350A hardware manual before ordering.
Q: How does the MR-J2S-350A differ from the MR-J2S-350A1 variant sometimes listed in industrial parts databases?
A: The MR-J2S-350A1 is a minor revision of the MR-J2S-350A with specific component changes made during the production run — the functional performance, parameter set, and servo motor compatibility are identical between the two revision levels. In most maintenance replacement scenarios, the MR-J2S-350A and MR-J2S-350A1 are interchangeable without modification to the machine program or servo parameters. Verify the specific revision compatibility with Mitsubishi technical support if the machine application is unusually sensitive to amplifier firmware differences.
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