Mitsubishi MR-J2S-200A — MELSERVO-J2-Super Series 2 kW AC Servo Amplifier

The Drive at a Glance

Introduced as part of Mitsubishi Electric's MELSERVO-J2-Super platform, the MR-J2S-200A is a 2 kW general-purpose AC servo amplifier designed for machine tools, packaging lines, semiconductor handling equipment, and a broad range of industrial automation applications. It handles position control, speed control, and torque control from a single unit — and uniquely among servo drives of its era, allows the control mode to be switched in real time: position/speed, speed/torque, or torque/position, without re-wiring or swapping hardware.

For facilities running existing MELSERVO-J2-Super installations, this amplifier is a direct drop-in. For engineers evaluating it for a new design, the combination of a 131,072 pulses/revolution absolute encoder standard on all compatible motors, a built-in dynamic brake, a built-in regenerative resistor, and a cooling fan in a single enclosed package makes commissioning significantly more straightforward than older-generation drives that required these as external options.

Electrical Specifications

Built-in Features Worth Noting

Two items that often show up as extra line items on competing drives come included as standard on the MR-J2S-200A: a dynamic brake and a regenerative resistor. The dynamic brake engages automatically when the servo is de-energised or an emergency stop is triggered, dissipating kinetic energy through the drive itself rather than relying on the machine's mechanical braking. The built-in regenerative resistor handles the energy returned to the DC bus during deceleration — adequate for typical duty cycles at this power level. Applications involving very frequent deceleration from high speed, or those with large inertia loads, can connect an external regenerative brake option if the internal resistor's thermal capacity is exceeded.

A forced air cooling fan is integrated into the MR-J2S-200A housing, distinguishing it from the smaller amplifiers in the J2-Super range (the 100A and below) which are naturally cooled. This allows the 2 kW model to run at full rated output without the derating that would otherwise be required in enclosed panels without forced airflow.

Compatible Servo Motors

The MR-J2S-200A pairs exclusively with the following Mitsubishi MELSERVO motor models. All listed motors use the 131,072 ppr serial absolute encoder as standard:

HC-SFS Series (2,000 r/min, medium inertia, IP65): HC-SFS121, HC-SFS152, HC-SFS153, HC-SFS201, HC-SFS202, HC-SFS203

HC-RFS Series (2,000 r/min, low inertia, IP65): HC-RFS103, HC-RFS153

HC-UFS Series (flat-body, IP55): HC-UFS152

HC-LFS Series: HC-LFS152

Brake-equipped variants (suffix "B") and reduction gear variants of all the above are equally supported. Note that the HC-KFS and HC-MFS motor families (3,000 r/min series) connect to the smaller MR-J2S amplifiers (100A and below) rather than the 200A.

Control Modes

Three primary control modes are available on the MR-J2S-200A, selectable by parameter:

Position control mode — The amplifier receives pulse-train commands from a PLC, motion controller, or pulse generator and tracks position with electronic gear interpolation. Input formats supported include sign + pulse, forward/reverse pulse, and 90° phase-difference (A/B quadrature) — switchable by parameter, not hardware.

Speed control mode — Speed reference arrives as an analogue voltage of 0 to ±8 V DC on the VC terminal (input impedance 10–12 kΩ). Internal speed presets (up to three speeds selectable by digital inputs) are also available for applications that don't require a continuous analogue reference.

Torque control mode — A 0 to ±8 V DC analogue torque command reference, with torque limit settable by parameter or by a separate 0 to +10 V DC external input. Useful for tension control, winding, or press-fit applications where force repeatability matters more than position accuracy.

Mode switching in real time (P/S, S/T, T/P) is handled by a dedicated digital input — no drive restart required.

I/O and Communications

Digital inputs (8 channels, 24 V DC, sink or source compatible): Servo-on (SON), forward/reverse limit switches (LSP/LSN), emergency stop (EMG), reset (RES), proportional control (PC/ST1/RS2), torque limit/speed selection (TL/ST2/RS1), speed selection (SP2) — all standard, additional functions assignable by parameter.

Digital outputs: Relay contact and open-collector outputs for in-position, speed reached, torque limiting, alarm, and brake release signals.

Analogue monitor (CN3): Two analogue voltage outputs reflecting real-time servo status (speed, torque, position error). These feed directly into an oscilloscope for gain tuning without MR Configurator software active.

RS-232C / RS-422 (CN3): PC connection for MR Configurator parameter software, real-time monitoring, alarm history, and auto-tuning. RS-422 supports multi-drop connection of up to 32 amplifiers on a single cable for batch monitoring on large installations.

Protection Functions

The MR-J2S-200A monitors the following conditions and shuts down or alarms before hardware damage occurs:

Overcurrent · Regenerative overvoltage · Overload (electronic thermal relay) · Servo motor overheat · Encoder signal error · Regenerative brake fault · Undervoltage / instantaneous power failure · Overspeed · Excessive position error

A five-digit seven-segment LED display on the front panel shows alarm codes directly, and alarm history is stored internally — accessible without a laptop by using the front-panel MODE and SET keys.

Auto-Tuning and Vibration Suppression

Gain adjustment on the MR-J2S-200A operates in three modes. Automatic tuning mode 1 sets PID gains by continuously estimating load inertia from the motor's torque and speed response — no test move required. Automatic tuning mode 2 adds feedforward gain to the estimation loop for applications with rapidly changing loads. Manual mode gives full parameter-level control for engineers who prefer to tune by hand or who are matching gains to an existing machine baseline.

An anti-microvibration function specific to the J2-Super platform suppresses the ±1 pulse oscillation that older servo drives produce when stopped at a position command boundary — a detail that matters most in precision positioning machines where even sub-millimetre dither at the tool is unacceptable.

Availability note: The MR-J2S series was discontinued by Mitsubishi Electric, with official service support having ended. Units continue to circulate through certified surplus channels and specialist industrial automation suppliers. This amplifier is available new-old-stock (NOS) or refurbished. For engineers planning new installations, Mitsubishi's current MR-J4 and MR-J5 series offer the recommended migration path, with renewal kits and motor conversion cables available to ease the transition from existing J2-Super hardware.

FAQ

Q1: Which Mitsubishi servo motors are compatible with the MR-J2S-200A?

The MR-J2S-200A is designed specifically for Mitsubishi's 2 kW-class servo motors in the HC-SFS, HC-RFS, HC-UFS, and HC-LFS families. Confirmed compatible models include HC-SFS121, HC-SFS152/153, HC-SFS201/202/203, HC-RFS103, HC-RFS153, HC-UFS152, and HC-LFS152 — along with their brake-equipped (B suffix) and reduction gear variants. The HC-KFS and HC-MFS families (3,000 r/min, small-frame motors) are not rated for use with the 200A; those motors pair with the MR-J2S-100A or smaller amplifiers in the same series. Motor and amplifier combinations outside the published compatibility table in the instruction manual SH030006 should not be attempted, as encoder protocol and parameter sets are matched to specific motor types.

Q2: Can the MR-J2S-200A accept a single-phase power supply?

Yes, with a limitation. Three-phase 200–230 V AC is the standard input, but 1-phase 230 V AC is also supported — connect to L1 and L2 and leave L3 open. Note that continuous output current may need to be derated when running single-phase at full load due to the higher ripple on the DC bus. For installations where only single-phase supply is available, verify that the driven load's duty cycle does not push the amplifier into sustained peak current demand, and consider whether an external DC reactor is warranted to reduce input harmonic distortion.

Q3: How is absolute position retained when the MR-J2S-200A is powered off?

Adding an MR-BAT battery unit to the CN4 battery connector on the amplifier converts the standard 131,072 ppr incremental encoder output from the servo motor into a full absolute position detection system. With the battery installed, the amplifier retains the motor's shaft position across power cycles, eliminating the need for a home-position return at every startup. Without the battery, the encoder functions as a high-resolution incremental type — position is accurate during operation but is lost at power-down. Battery replacement interval depends on operating conditions; Mitsubishi generally recommends checking battery voltage after three to five years of service.

Q4: What is the difference between the MR-J2S-200A and the MR-J2S-200B?

Both are 2 kW amplifiers from the same J2-Super platform and share the same servo motor compatibility. The "-A" suffix indicates a general-purpose interface — pulse-train and analogue command inputs, compatible with virtually any PLC or motion controller. The "-B" suffix indicates an SSCNET interface (Mitsubishi's proprietary fibre-optic servo network), which requires a Mitsubishi SSCNET-capable motion controller such as the Q172D or Q173D. If your motion controller is from a third-party manufacturer, the MR-J2S-200A (A-type) is the correct choice. If you are running a fully Mitsubishi motion system, the B-type may offer simpler wiring and tighter synchronisation across multiple axes.

Q5: The MR-J2S series has been discontinued — is it still worth sourcing?

For facilities already running J2-Super equipment, replacing a failed MR-J2S-200A with a like-for-like unit is almost always faster and more economical than a full system migration. A full upgrade to MR-J4 or MR-J5 involves new motor-side cabling, encoder conversion cables, parameter re-mapping, and potentially mechanical changes at the motor mounting — work that is feasible but requires planned downtime. Where a machine is otherwise healthy and production-critical, sourcing a tested NOS or refurbished MR-J2S-200A is a legitimate and common choice. The main risk with surplus units is undisclosed storage history; buying from a supplier who performs electrical load testing before shipment is strongly advisable.