The MR-J2S-20A is Mitsubishi Electric’s 200 W 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 200 W continuous servo control for HC-KFS23 and HC-MFS23 series servo motors in active J2S-based servo systems where direct maintenance replacement of failed units is required. Atlantech Drives holds stock of the MR-J2S-20A. Contact us for fast worldwide delivery and competitive pricing.
What Is the MR-J2S-20A?
The MR-J2S-20A is a MELSERVO-J2 Super series servo amplifier providing 200 W (0.2 kW) continuous output power for Mitsubishi HC-KFS23, HC-MFS23, and equivalent 200 W servo motors with the J2S-era absolute encoder (2,048 pulses/rev incremental with multi-turn counting, 17-bit equivalent). The «J2S» designation identifies the second-generation MELSERVO Super platform — a major upgrade from the original J2 series providing improved encoder resolution, faster auto-tuning, and the then-new SSCNET network capability in the J2S-B variants. The MR-J2S-20A accepts position command pulses from a host controller via open-collector or differential RS-422A pulse input, implementing the J2S three-loop servo control architecture with current loop bandwidth of approximately 1.5 kHz — lower than the 2 kHz of the MR-J3 and 3.5 kHz of the MR-J4, reflecting the older control processor technology. The MR-J2S-20A does not include a built-in STO safety function and uses older servo parameter architecture accessible via the legacy MR Configurator software (not MR Configurator2 — verify compatibility before ordering if MR Configurator2 is the only available software tool). The MR-J2S-20A represents a two-generation older product than the current MR-J4-20A and should be specified only for like-for-like maintenance replacement when the full system (motor, controller, cabling) is to be retained without modification.
Key Technical Specifications
- Model: MR-J2S-20A
- Rated Output Power: 200 W (0.2 kW)
- Power Supply: 200–240 VAC single-phase or three-phase, 50/60 Hz
- Continuous Output Current: 1.5 A
- Maximum Output Current: 4.5 A (3× continuous peak)
- Compatible Servo Motors: HC-KFS23, HC-MFS23 (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 (2,048 pulses/rev incremental base with multi-turn absolute function)
- Safety Function: None built-in
- Regenerative Brake: Built-in
- Communication: RS-232C (MR Configurator legacy software)
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 40 mm × 130 mm × 120 mm
- Weight: Approx. 0.7 kg
Architecture & Design Overview
The MR-J2S-20A implements the MELSERVO-J2 Super servo control architecture — a digital three-loop controller using a dedicated servo DSP processing the position, speed, and current loops in firmware, with the control computation rate approximately 88 µs per control cycle (compared to approximately 62 µs for the MR-J3 and 31 µs for the MR-J4). The encoder interface uses a proprietary serial encoder protocol specific to the J2S/J3-era HC-KFS and HC-MFS motor series — this encoder protocol is not compatible with the 17-bit or 22-bit encoder systems used by MR-J3 and MR-J4 amplifiers, meaning that servo motor changes between J2S and J3/J4 generations require motor replacement along with amplifier replacement. The MR-J2S-20A’s auto-tuning function operates on the fundamental principle of mechanical inertia estimation, but with a more limited tuning algorithm than the J3 and J4 generations — in high-inertia systems or systems with significant friction, manual gain adjustment is frequently required after auto-tuning to achieve adequate servo performance. The amplifier’s communication interface uses RS-232C (9-pin D-Sub) rather than the USB interface of MR-J3 and MR-J4 amplifiers — a modern PC without an RS-232C port requires a USB-to-RS-232C adapter to connect to MR Configurator. MR Configurator2 (the current Mitsubishi servo commissioning tool) has limited or no support for MR-J2S parameter access — verify MR Configurator compatibility before attempting to configure the MR-J2S-20A with MR Configurator2.
Replacement & Upgrade Notes
The MR-J2S-20A is two generations removed from current Mitsubishi servo technology and represents a significantly more challenging maintenance replacement scenario than MR-J3 parts — the combination of discontinued production, aging installed base, and incompatibility with current servo motors and commissioning tools makes MR-J2S-20A sourcing increasingly difficult. For direct like-for-like replacement where the HC-KFS23 or HC-MFS23 motor and all associated wiring are being retained, the MR-J2S-20A is the required specification — no current-generation amplifier is directly backward compatible with J2S-era HC-KFS and HC-MFS motor encoders. For planned upgrades from MR-J2S-20A to current technology, the minimum replacement requires both the amplifier (MR-J2S-20A → MR-J4-20A) and the servo motor (HC-KFS23 → HG-KR23 or HG-MR23) simultaneously — the J2S encoder is not readable by J4 amplifiers even in compatibility mode, making motor-only or amplifier-only upgrade impossible. Additional changes required for a complete J2S-to-J4 upgrade include updated pulse command wiring (if the pulse train cable connector type differs), updated encoder cable (J2S encoder cable is not compatible with J4 amplifier encoder connector), and complete servo re-tuning using MR Configurator2. For facilities with multiple MR-J2S-20A units, the total cost of upgrading all units (amplifiers + motors + cables + commissioning) should be evaluated against the risk-adjusted cost of continued operation on J2S hardware — increasingly expensive emergency sourcing, longer lead times, and potential extended downtime on motor failures (which require finding J2S-compatible replacement motors) all support proactive upgrade over reactive maintenance for machines with 10+ year J2S installations.
Frequently Asked Questions
Q: Can MR Configurator2 (the current Mitsubishi software) configure the MR-J2S-20A?
A: MR Configurator2 support for MR-J2S amplifiers is limited — while some parameter viewing may be possible, full parameter editing, auto-tuning, and waveform monitoring may require the legacy MR Configurator software (not MR Configurator2). Verify MR-J2S compatibility in the MR Configurator2 release notes or by contacting Mitsubishi technical support before assuming MR Configurator2 will provide full MR-J2S-20A configuration capability.
Q: Is any current-generation Mitsubishi servo motor compatible with the MR-J2S-20A amplifier?
A: No current-generation Mitsubishi servo motor (HG-KR, HG-MR, HG-SR, HG-RR series) is compatible with the MR-J2S-20A amplifier — the J2S encoder protocol is specific to the HC-KFS and HC-MFS motor series and is not supported by any J3 or J4 era motors. The MR-J2S-20A can only drive HC-KFS23 and HC-MFS23 motors with the J2S-era encoder. If the HC motor has failed and cannot be sourced, a complete simultaneous replacement of both the MR-J2S-20A amplifier and the motor (with a current-generation pair such as MR-J4-20A + HG-KR23) is the only viable path forward.
Q: What is the maximum input pulse frequency of the MR-J2S-20A compared to the MR-J3-20A?
A: The MR-J2S-20A accepts differential pulse input at up to 500 kpps and open-collector input at up to 200 kpps. The MR-J3-20A accepts differential input at up to 4 Mpps (4,000 kpps) — eight times higher than the J2S maximum. In practice, the 500 kpps J2S limit is adequate for most stepper-like pulse positioning applications, but it restricts the maximum axis speed at high encoder resolution — at 2,048 pulses/rev and 500 kpps maximum pulse rate, the maximum motor speed is approximately 14,600 RPM, which exceeds most servo motor mechanical limits. For positioning modules generating pulses below 500 kpps, the J2S pulse input limitation is not a practical constraint.
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