Mitsubishi MR-J4-350A Servo Amplifier

(MELSERVO-J4 Series, 3.5 kW)

MR-J4: 4th-generation high-performance servo amplifier of J4 series

350: Rated power 3.5 kW

A: Pulse + analog general-purpose interface (hard-wired command, no SSCNET optical fibre bus). Bus version: MR-J4-350B. Suffix -RJ: Supports external linear encoder for full closed-loop control.

⚠️ Models of 3.5 kW and higher only accept 3-phase AC200-240V main power supply. Single-phase supply is NOT allowed.

Core Electrical Specifications

Compatible Servo Motors (200V Class)

Medium inertia: HG-SR352, HG-SR353; With brake: HG-SR352B, HG-SR353B

Low inertia: HG-KR353, HG-KR353B (with brake)

J2S / JE series motors cannot be used directly due to encoder protocol incompatibility.

Interface Overview

1. CN1: I/O signal terminal block, pulse/direction, ±10V analog input, digital DI/DO, STO safety circuit
2. CN2: Motor encoder connector
3. CN3: USB service port, for PC connection with MR-Configurator2 for commissioning, monitoring and parameter backup
4. CN4: Full-closed-loop linear encoder interface (activated for -RJ variant only)
5. Main circuit terminals: L1/L2/L3 main power; U/V/W to motor; B1-B2 for external regenerative resistor.

Main Features

Three switchable control modes: Position, Speed, Torque. Compatible with pulse-output PLC (FX/Q/L/R series) and 3rd-party pulse motion controllers.

Advanced Vibration Suppression Ⅱ, adaptive filter, auto-tuning, ToughDrive instantaneous power failure protection, quadrant protrusion compensation, machine diagnosis function.

A/B/Z phase encoder pulse output, 2-channel analog monitor output.

Drop-in replacement for MR-J3-350A (mechanical mounting compatible; parameters require re-tuning).

Alternative Selection Reference

1. Same series bus version: MR-J4-350B (SSCNET Ⅲ/H optical fibre bus, for multi-axis synchronous systems)
2. New-generation upgrade: MR-J5-350A (higher bandwidth; hardware mounting not fully compatible, wiring and motor compatibility to be verified).
3. Retrofit for legacy equipment: Upgrade MR-J3-350A to this unit; pay attention to regenerative resistor and parameter migration.

Second-hand Unit Inspection Checklist

1. Visual check: Burnt marks, scorched terminals, bulging capacitors.
2. Insulation test: Megger test between main-circuit U/V/W and protective earth.
3. Power-on without motor: Check for alarms; verify STO circuit status.
4. No-load motor jog test: Check abnormal noise, vibration and encoder feedback.
5. Use MR-Configurator2 to read internal alarm history.

Common Alarms

AL.30: Regenerative error. Check regenerative resistor sizing. External resistor is mandatory for frequent start-stop or vertical axis applications.

AL.16: Encoder communication error. Inspect CN2 cable and connectors.

AL.E6: STO circuit open. CN1 STO terminals not short-circuited or external safety signal triggered.

Supplementary Notes for MR-J4-350A (Section 2)

2. Typical Pulse-Direction Wiring for Position Control

CN1 terminals, differential signalling (recommended for high noise immunity, for PLC differential output)

1. Pulse command: PP ← PLC pulse output; NP ← pulse negative
2. Direction command: PD ← PLC direction output; ND ← direction negative
3. STO safety circuit: Short-circuit STO1-STO2 and STO3-STO4 on CN1, otherwise AL.E6 occurs and servo cannot run.
4. DC24V control supply: DICOM to 24V+; DOCOM to 24V-.

Parameter Settings for Pulse-Direction Mode

Open-collector Mode (Legacy PLC, not recommended for long cable runs)

Max. pulse frequency limited to 200 kpps; cable length ≤3 m, susceptible to electromagnetic interference.

Wiring Precautions

1. L1/L2/L3 must be fed with 3-phase 200-240V AC. Never apply single-phase 220V to MR-J4-350A, power-supply fault alarm will trigger.
2. Incorrect U/V-W phase sequence causes shaking and AL.37 alarm.
3. Use Mitsubishi shielded servo cable for CN2 encoder wiring; shield grounding at both ends.

Commissioning Software

MR-Configurator2. Connect PC USB to CN3 for jog operation, auto-tuning, alarm history reading and parameter backup.

Full Differences & Replacement Guide: MR-J4-350A replacing MR-J3-350A

Original unit: MR-J3-350A; Replacement unit: MR-J4-350A; Both 3.5 kW, 200V class.

1. Mechanical Installation & Hardware
2. Mounting cut-out fully compatible: Screw hole positions match, direct retrofit without cabinet modification.
3. Overall dimensions nearly identical; heat-sink layout differs without impact on fitting.
4. Main-circuit terminals L1/L2/L3, U/V/W, B1-B2 for regenerative resistor: pin-to-pin identical. Existing power cables and external regenerative resistor can be reused.
5. ✅Major difference: CN1 control I/O connector

MR-J3-350A: Spring-clamp terminal block

MR-J4-350A: Removable plug-in connector

Field retrofit note: Existing MR-J3 CN1 harness cannot plug directly into MR-J4. Two options:

① Purchase dedicated CN1 plug for MR-J4 and re-terminate existing wires.

② Keep old J3 terminal block and implement external flying-wire adapter.

5. CN2 encoder connector: Same physical plug, different protocol

MR-J4-350A can drive legacy MR-J3 HF-SP352 motor (firmware version A8 or above).

MR-J3 cannot drive J4-series HG-SR motors.

Physical encoder cable plug fits, double-check for vertical axes; use genuine shielded cables.

6. New CN3 USB service port (absent on MR-J3). Use MR-Configurator2 for setup.
7. STO safety circuit (Root cause for AL.E6)

MR-J3 has no built-in STO safety function.

MR-J4 STO terminals are open by factory default. Short-circuit STO1-STO2 and STO3-STO4 on CN1, otherwise AL.E6 appears immediately after power-on. This is the most frequent field pitfall during replacement.

2. Regenerative Resistor Comparison

Existing external regenerative resistor can remain in-service. For frequent start-stop or vertical-axis loads, do not rely solely on internal resistor; keep external resistor connected.

3. Motor Compatibility
4. ✅MR-J4-350A supports legacy HF-SP352 / HF-SP352B motors from J3 platform, firmware ≥A8 required.
5. ❌MR-J3-350A cannot drive J4-series HG-SR352 motors.
6. Motor power cables: mechanically interchangeable for reuse. Encoder cables share identical plug but differ in protocol; legacy HF-motor cables are acceptable.
7. Parameter Migration (Do NOT import MR-J3 parameter files directly)

MR-J3 parameter files cannot be loaded into MR-J4. Partial parameter numbers have changed; enter values manually, do not copy all parameters wholesale.

Key Parameter Mapping (Pulse-Direction Position Mode)

MR-J4 accepts higher pulse frequency (4Mpps differential, MR-J3 only 1Mpps). Higher pulse rates from PLC are achievable after replacement.

Tuning Remarks

MR-J4 implements Advanced Vibration Suppression Ⅱ and adaptive filter gains. Do not copy gain values directly from MR-J3. Run auto-tune after replacement and fine-tune gains.

5. Step-by-Step Power-on Retrofit Procedure
6. Power off equipment; remove MR-J3-350A and mount MR-J4-350A in-situ.
7. Retain existing wiring for main-circuit L1/L2/L3, U/V/W and B1-B2 regenerative resistor.
8. Process CN1: Fit dedicated MR-J4 plug; short-circuit STO1-STO2 and STO3-STO4 to prevent AL.E6.
9. Connect CN2 encoder cable. For legacy HF-SP motors, confirm drive firmware ≥A8.
10. Power-on; perform factory reset first, then manually input critical parameters (mode, pulse-input format, electronic gear ratio).
11. No-load jog test to verify rotation direction. Reverse direction by modifying bit setting inside Pr.000 (software reversal), do not swap U/V/W power phases.
12. Execute auto-tune. Run machine under load; monitor for vibration or noise. Watch regenerative load factor to avoid AL.30 regenerative error.
13. Typical Replacement-related Faults
14. AL.E6: STO circuit not short-circuited. MR-J3 lacks STO, this fault is highly common in retrofits.
15. AL.16 Encoder error: Legacy J3 motor used with outdated drive firmware → upgrade firmware.
16. Poor positioning accuracy / vibration: Do not reuse J3 gain settings; perform new auto-tuning.
17. AL.30 Regenerative error: Frequent start-stop / vertical axis → inspect external regenerative resistor.
18. No response to pulse command: Double-check Pr.001 pulse-input-mode setting.
19. PLC Program Considerations

Power-up initialization duration differs between MR-J3 and MR-J4. For vertical-axis machines, add a short delay in PLC logic after servo-ready signal to prevent axis dropping.