The MR-J2S-500A is Mitsubishi Electric’s 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 — one of the highest-power models in the MR-J2S-A pulse train sub-series, providing 5 kW continuous servo control at 23 A for HC-SFS502 and HC-RFS503 series servo motors in active J2S-based heavy-duty servo systems where direct maintenance replacement is the primary requirement. The MR-J2S-500A is available through Atlantech Drives — quote within 24-48 hours, worldwide express shipping, 12-month warranty.
What Is the MR-J2S-500A?
The MR-J2S-500A is a MELSERVO-J2 Super series servo amplifier providing 5 kW (5,000 W) continuous output power for Mitsubishi HC-SFS502, HC-RFS503, and equivalent 5 kW servo motors with the J2S-era serial encoder protocol. As the upper range of the MR-J2S-A standard catalogue, the MR-J2S-500A was specified for the most demanding pulse-train-commanded servo axis applications of the J2S era — large CNC machining centre spindle and main feed axis drives, heavy industrial robot base axes, and large-format processing machine primary traverse drives where 5 kW of continuous servo power provides the sustained torque required at the rated rapid traverse and cutting speeds. The MR-J2S-500A accepts position command pulses via differential RS-422A or open-collector input, implements the J2S three-loop servo control architecture with approximately 1.5 kHz current loop bandwidth, and communicates with the legacy MR Configurator software via RS-232C. Three-phase 200–240 VAC supply is required at full 5 kW output — while single-phase supply is technically supported at reduced power levels, full-rated 5 kW output requires three-phase supply for balanced current draw. The MR-J2S-500A does not include a built-in STO safety function, requiring an external safety contactor rated for 23 A at 200 VAC for safety compliance.
Key Technical Specifications
- Model: MR-J2S-500A
- Rated Output Power: 5 kW (5,000 W)
- Power Supply: 200–240 VAC single-phase or three-phase, 50/60 Hz
- Continuous Output Current: 23.0 A
- Maximum Output Current: 69.0 A (3× continuous peak)
- Compatible Servo Motors: HC-SFS502, HC-RFS503 (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 (external safety contactor required)
- 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): 130 mm × 240 mm × 178 mm
- Weight: Approx. 4.0 kg
Architecture & Design Overview
The MR-J2S-500A implements the MELSERVO-J2 Super three-loop digital servo control architecture at 5 kW scale, using a dedicated servo DSP processing position, speed, and current control loops at approximately 88 µs per control computation cycle. The IGBT power stage provides three-phase variable voltage, variable frequency output to the servo motor from the rectified 200 VAC DC bus (approximately 280 VDC), with the current control loop maintaining the commanded torque via closed-loop PWM modulation at approximately 10 kHz switching frequency. The J2S-era auto-tuning algorithm estimates the load inertia ratio by analysing the servo response to a series of controlled velocity steps, setting the servo proportional and integral gains to achieve stable response at the identified inertia ratio. Compared to the MR-J3 and MR-J4 auto-tuning algorithms, the J2S auto-tuning provides adequate results for standard mechanical systems but may require additional manual adjustment for high-inertia systems (inertia ratio above 15:1) or systems with significant friction. The MR-J2S-500A’s encoder interface is the J2S proprietary serial encoder protocol — this protocol is specifically designed for the HC-SFS and HC-RFS motor series and is not compatible with any encoder used in MR-J3 or MR-J4 era motors. The amplifier’s RS-232C communication port operates at 9,600 bps or 19,200 bps for parameter read/write communication with MR Configurator — this low-speed serial interface reflects the technology standards of the J2S design era and is substantially slower than the USB interface of current-generation amplifiers, making full parameter read/write sessions noticeably longer than with MR-J3 or MR-J4 amplifiers.
Maintenance Tips
The MR-J2S-500A at 5 kW generates significant heat during sustained high-load operation, making cooling fan maintenance the highest-priority preventive maintenance task for units approaching 10+ years of service. The cooling fan’s bearing life at 40°C ambient is approximately 30,000–40,000 hours — for machines operating 16 hours per day, this corresponds to approximately 5–7 years before the fan bearing reaches rated life. Replace the MR-J2S-500A cooling fan every 4–5 years regardless of observed condition, scheduling the replacement during planned maintenance windows to avoid the unplanned downtime of emergency cooling fan failure. The DC bus electrolytic capacitors in the MR-J2S-500A have rated service life of approximately 10 years at 40°C — units in service beyond 12 years should be evaluated for proactive capacitor replacement by a qualified servo drive repair specialist before catastrophic capacitor failure causes secondary damage to the power stage IGBT module. Maintain the complete MR-J2S-500A parameter set as a backup file in the MR Configurator .par file format stored with the machine documentation — this backup enables rapid parameter restoration after an emergency replacement without relying on parameter printouts or machine drawings that may be incomplete. For machines where the MR-J2S-500A’s RS-232C cable has been lost or damaged over the years, a 9-pin D-Sub to 9-pin D-Sub null modem cable with crossed RxD/TxD pins is required for MR Configurator communication — standard straight-through RS-232C extension cables will not establish communication with the MR-J2S-500A.
Frequently Asked Questions
Q: Is there any current-generation Mitsubishi servo amplifier that can replace the MR-J2S-500A while retaining the existing HC-SFS502 servo motor?
A: No current-generation Mitsubishi servo amplifier (MR-J3, MR-J4, or MR-JE series) is compatible with the HC-SFS502 motor’s J2S encoder protocol. A like-for-like MR-J2S-500A replacement (from aftermarket inventory) is the only path to retaining the existing HC-SFS502 motor. Upgrading to any current-generation amplifier requires simultaneous motor replacement — MR-J2S-500A + HC-SFS502 → MR-J4-500A + HG-SR502, along with new encoder cable, potentially new motor power cable, and complete servo re-tuning.
Q: Can the MR-J2S-500A operate in torque control mode for tension winding applications?
A: Yes. The MR-J2S-500A supports torque control mode via the analogue torque command input (VC terminal), where the analogue voltage (±10 VDC) proportionally commands the motor torque as a percentage of rated torque. This mode is used for winding, unwinding, and tension control applications where the motor must maintain constant torque rather than follow a position or speed command. Select torque control mode via amplifier parameter PA01 and connect the tension control signal to the VC terminal on the CN1 connector.
Q: What is the expected availability horizon for MR-J2S-500A units in the aftermarket, and should spare units be stockpiled?
A: The MR-J2S-500A has been discontinued for 15+ years and the available aftermarket inventory is declining as units are consumed for maintenance replacement worldwide. Authentic units from reputable sources are still available as of 2025, but availability is expected to become more constrained over the next 2–5 years. For facilities with multiple MR-J2S-500A units in critical production equipment, maintaining a minimum of one spare unit per five installed units in controlled storage is recommended — the alternative of emergency sourcing at the time of failure carries increasing price premium and lead time risk as the available inventory pool shrinks.
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