Mitsubishi MR-J4-350A4-RJ

Within Mitsubishi's Servo lineup, the MR-J4-350A4-RJ functions as a 3.5 kW AC servo amplifier rated for 480V three-phase input, positioned in the upper-mid power tier of the MR-J4 fourth-generation series. The MR-J4 family represents Mitsubishi's current-generation motion control platform, designed to replace the earlier MR-J3 series across demanding industrial applications. At its core, the Mitsubishi MR-J4-350A4-RJ is a fully digital servo drive, translating commanded motion profiles into precise torque, velocity, and position outputs delivered to a paired servo motor. The "350" in the model designation corresponds to the 3.5 kW capacity, while "A4" denotes the 480V voltage class, distinguishing it from the standard 200V "A" variants in the same family. The "-RJ" suffix indicates built-in CC-Link IE Field Network Basic communication capability, setting it apart from base MR-J4 models that require separate network interface options. The unit operates as the intermediary between a motion controller or PLC and the mechanical load, continuously processing encoder feedback to maintain commanded motion with minimal positional error.

Integration-wise, the MR-J4-350A4-RJ is engineered to operate within Mitsubishi's iQ-R and iQ-F platform ecosystems, communicating natively with MELSEC series controllers over CC-Link IE Field Network Basic without requiring additional network cards. The drive is compatible with Mitsubishi's MR Configurator2 setup software, which provides parameter configuration, auto-tuning, and real-time oscilloscope diagnostics — reducing commissioning time on complex multi-axis installations. Compared to lower-capacity siblings in the MR-J4 line, this 3.5 kW, 480V variant is specifically suited for applications where higher torque output is required alongside compliance with North American 480V electrical infrastructure. The one-touch auto-tuning feature, shared across the J4 family, dynamically adjusts gain parameters to match varying load inertia without manual intervention. Industries that commonly deploy the Mitsubishi MR-J4-350A4-RJ include automotive body welding and stamping lines, CNC machine tool spindle positioning, packaging machinery, and semiconductor wafer handling systems where precise, repeatable motion is non-negotiable. The drive also supports advanced functions such as functional safety (STO — Safe Torque Off) to IEC 61800-5-2 standards, a feature increasingly mandated in collaborative industrial environments. Facilities sourcing motion control components can reference our Servo repair catalog to confirm compatibility with existing Mitsubishi infrastructure.

Like other Servo units in heavy industrial duty, the MR-J4-350A4-RJ is subject to predictable wear patterns tied to thermal cycling, capacitor aging, and sustained high-cycle operation in environments with airborne contaminants or vibration. In 480V installations, the DC bus capacitors and gate driver circuits are among the first components to show degradation, often manifesting as fault codes AL.30 (regenerative error), AL.32 (overcurrent), or AL.50 (overload) before complete failure occurs. Encoder communication faults — appearing as AL.16 or AL.1A — are also reported on units that have accumulated high operating hours, particularly in high-vibration machine tool and press applications. Facilities evaluating an MR-J4-350A4-RJ replacement due to repeated faults should cross-reference the fault history log in MR Configurator2 before assuming the amplifier is the root cause, as motor winding degradation can produce identical fault signatures. Operations looking to buy MR-J4-350A4-RJ stock as a spare or active replacement can source new, MR-J4-350A4-RJ refurbished, or repaired units depending on lead time constraints and budget. Mitsubishi's Mitsubishi Servo repair support chain covers this model, and component-level evaluation by qualified technicians can often recover units that appear failed at the system level. For full repair scope and turnaround options, see our industrial Servo repair services page for current availability and exchange pricing. Facilities can ship the MR-J4-350A4-RJ to Flexa Systems for board-level repair, exchange for a refurbished unit, or order new stock — repairs are backed by a 2-year warranty from our Lewisville, TX shop.