Mitsubishi MR-J2S-350A AC Servo Drive Amplifier – MELSERVO-J2-Super

Mitsubishi MR-J2S-350A — 3.5 kW AC Servo Drive Amplifier in the MELSERVO-J2-Super Series

The MR-J2S-350A is a 3.5 kW capacity AC servo drive amplifier from Mitsubishi Electric’s MELSERVO-J2-Super (MR-J2S) platform. Designed for closed-loop motion control in industrial machinery, this unit governs the torque, velocity, and position of matched servo motors through sinusoidal PWM current regulation. Its role in a control loop is to receive command pulses or analog references from an upstream controller — typically a MELSEC PLC or CNC unit — and translate those references into precise three-phase output current waveforms that drive the motor shaft to the commanded state with minimal lag and overshoot.

At 3.5 kW, the MR-J2S-350A occupies the mid-range of the J2-Super family, bridging the gap between lighter-duty positioning axes and the high-inertia drives used in heavy gantry or winding applications. The amplifier accepts three-phase or single-phase 200–230 V AC mains input, rectifies it to a regulated DC bus, and synthesises the output waveform through an IGBT inverter stage. The current control loop operates at a bandwidth sufficient to suppress torque ripple below 1% of rated torque under steady-state conditions, which is a prerequisite for surface-finish quality in grinding and honing applications.

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Technical Parameters

Hardware Logical Analysis

The MR-J2S-350A’s internal architecture is built around a dedicated DSP that executes the current, velocity, and position control loops in a deterministic sequence. The current loop — the innermost and fastest — runs at a fixed 88 µs cycle, which is short enough to track the sinusoidal reference waveform at motor speeds up to 4,500 rpm without phase lag accumulation. The velocity loop closes at 0.444 ms, and the position loop at 0.888 ms. These nested loop periods are not configurable by the user, which is a deliberate design choice: fixed timing eliminates jitter-induced positioning error that would otherwise appear as surface waviness in precision machining.

EMC Architecture: The drive’s DC bus is decoupled from the IGBT gate-drive circuitry by an isolated gate driver IC with a common-mode rejection ratio exceeding 50 dB. The input rectifier stage incorporates a three-phase line reactor equivalent (internal impedance) that limits di/dt on the mains side, reducing conducted emissions in the 150 kHz–30 MHz band. For installations requiring CE EMC compliance, an external FR-BIF or equivalent Class C2 line filter is recommended; the drive’s internal filtering alone meets Class C3 limits per IEC 61800-3.

Vibration Suppression: The adaptive notch filter embedded in the velocity loop can identify and suppress mechanical resonance frequencies between 10 Hz and 2,250 Hz. The filter centre frequency is updated in real time based on FFT analysis of the velocity feedback signal, without requiring the machine to be stopped. This is particularly relevant for long ball-screw axes where the first torsional resonance mode typically falls between 80 Hz and 300 Hz depending on screw diameter and unsupported length.

Absolute Encoder Battery Backup: When paired with an absolute encoder motor (HC-SFS352B or equivalent), the MR-J2S-350A maintains encoder position data through a 3.6 V lithium battery (MR-BAT) connected at CN4. The battery sustains SRAM retention for a minimum of 10,000 hours at 25 °C. On power restoration, the drive reads the stored multi-turn counter and single-turn position register, reconstructing absolute position without a homing cycle. The battery voltage is monitored continuously; an AL.92 alarm is generated when voltage drops below 3.1 V, providing advance warning before data loss occurs.

Regenerative Energy Path: During deceleration, kinetic energy from the motor and load is returned to the DC bus as regenerative current. The MR-J2S-350A’s built-in resistor can absorb up to 100 W continuously and 3,500 W peak (for short duty cycles). For applications with high-inertia loads — rotary tables, winding mandrels, or vertical axes with counterweights — the external MR-RB032 (30 Ω, 100 W) or MR-RB12 (13 Ω, 100 W) resistors extend the permissible regenerative duty cycle. The drive monitors bus voltage and switches the regenerative transistor at a threshold of approximately 400 V DC, preventing bus overvoltage faults during rapid deceleration ramps.

System Integration Benefits

• Native MELSEC PLC Compatibility: The MR-J2S-350A accepts differential pulse train input (up to 500 kpps) directly from MELSEC Q-series, L-series, and iQ-R positioning modules without an intermediate signal converter, reducing wiring complexity and eliminating pulse-count errors caused by single-ended signal degradation over cable runs exceeding 2 m.
• MR Configurator2 Diagnostic Transparency: The RS-422 interface provides real-time oscilloscope-class waveform capture of torque command, motor speed, position error, and bus voltage at 88 µs resolution. Engineers can diagnose mechanical resonance, load inertia mismatch, and cable fault conditions without external instrumentation.
• Gain Auto-Tuning: One-touch tuning measures load inertia ratio in under 3 seconds and sets proportional, integral, and derivative gains for the velocity loop automatically. The resulting gain set is stored in non-volatile EEPROM and survives power cycling, eliminating re-tuning after maintenance shutdowns.
• Switchable Control Modes: Position, speed, and torque modes are selectable via digital input signals (CN1B pins) without firmware changes. This allows a single drive to serve dual roles — for example, operating in torque mode during a winding tension phase and switching to position mode for a cut-and-register step — within the same machine cycle.
• Fault History Logging: The drive stores the last 16 alarm codes with timestamps in non-volatile memory, accessible via MR Configurator2 or the front-panel display. Each alarm record includes the motor speed, torque command, and bus voltage at the moment of fault, providing root-cause data without requiring a data logger.
• Inertia Ratio Monitoring: The drive continuously estimates load-to-motor inertia ratio during normal operation. A sudden change in the estimated ratio — for example, a 30% increase — can indicate a mechanical coupling failure or gearbox wear, enabling condition-based maintenance scheduling before a catastrophic failure occurs.
• Backward Compatibility with MR-J2 Series: The MR-J2S-350A is a drop-in electrical and mechanical replacement for the earlier MR-J2-350A. Connector pinouts, mounting hole patterns, and parameter structures are preserved, allowing field upgrades without panel redesign or PLC program modification.
• Multi-Axis Synchronisation via MELSEC Motion CPU: When controlled by a Q172DCPU or Q173DCPU motion controller, the MR-J2S-350A participates in synchronous multi-axis interpolation at the SSCNET (Servo System Controller NETwork) level, achieving axis-to-axis synchronisation error below ±1 pulse count across up to 32 axes.

Quality Assurance & Global Logistics

Every MR-J2S-350A unit dispatched from our Xiamen, China facility is sourced directly from Mitsubishi Electric’s authorised distribution network. Authenticity is verified through manufacturer lot codes, date codes, and holographic labels cross-referenced against Mitsubishi Electric’s product traceability database. Units are not repackaged or relabelled; original factory packaging is preserved where available.

Pre-shipment inspection covers: DC bus capacitor ESR measurement, IGBT gate-drive signal integrity check, encoder interface continuity test, fan bearing acoustic check, and a full power-on functional test including fault-code readout and parameter initialisation. Each unit ships with a test record card documenting measured values.

Export logistics from Xiamen are handled through bonded warehouse channels with access to major international freight forwarders. Standard transit times: 3–5 business days to Southeast Asia, 5–7 days to Europe and North America via air freight, 25–35 days via sea LCL. All shipments include a commercial invoice, packing list, and certificate of origin. HS Code 8504.40 (static converters) is declared on all export documents. EXW, FOB Xiamen, and CIF terms are available. The 12-month warranty covers manufacturing defects; field damage caused by incorrect wiring or parameter configuration is assessed case-by-case with repair quotation provided within 48 hours.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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