The MR-J3-700A is Mitsubishi Electric’s 7 kW MELSERVO-J3 series servo amplifier for 200 V three-phase AC power supply with pulse train position command input — a legacy servo amplifier from Mitsubishi’s third-generation MELSERVO platform, providing 7 kW continuous servo control at 37 A for HC-SFS702 and HC-RFS703 series servo motors in active high-power pulse-train-commanded servo systems requiring direct maintenance replacement. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the MR-J3-700A?
The MR-J3-700A is a MELSERVO-J3 series servo amplifier providing 7 kW (7,000 W) continuous output power for Mitsubishi HC-SFS702, HC-RFS703, and equivalent 7 kW servo motors with the MR-J3’s 17-bit multi-turn absolute encoder. As the highest standard-catalogue power level in the MR-J3-A pulse train sub-series at 200 V, the MR-J3-700A is specified for the most power-demanding single-axis pulse-train-commanded servo applications of the J3 era — large CNC machining centre feed axes, heavy robotic base axes, and large-format material handling drive systems where 7 kW of continuous servo power is required. The amplifier accepts position command pulses via open-collector or differential RS-422A input at up to 4 Mpps, implementing the MELSERVO-J3 three-loop servo control architecture with 2 kHz current loop bandwidth and Advanced Vibration Suppression Control (first-generation AVSC, single notch filter). Three-phase 200–240 VAC supply is required exclusively — at 7 kW and 37 A continuous output, single-phase operation is not rated. The MR-J3-700A does not include a built-in STO safety function, requiring an external safety contactor rated for the full 37 A motor operating current for IEC 62061 / EN ISO 13849 safety compliance. The MR-J3-700A has been superseded by the MR-J4-700A and should be specified for direct maintenance replacement only.
Key Technical Specifications
- Model: MR-J3-700A
- Rated Output Power: 7 kW (7,000 W)
- Power Supply: 200–240 VAC three-phase only, 50/60 Hz
- Continuous Output Current: 37.0 A
- Maximum Output Current: 111.0 A (3× continuous peak)
- Compatible Servo Motors: HC-SFS702, HC-RFS703, HG-SR702 (J4 motor, J3 compat. mode)
- Command Interface: Pulse train input (open-collector or differential RS-422A)
- Maximum Input Pulse Frequency: 4 Mpps (differential), 200 kpps (open-collector)
- Encoder Interface: Serial 17-bit absolute encoder (131,072 pulses/rev)
- Safety Function: None built-in (external safety contactor required)
- Regenerative Brake: Built-in, external MR-RB series resistor connectable
- Communication: USB (MR Configurator2), RS-422
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 170 mm × 260 mm × 200 mm
- Weight: Approx. 4.5 kg
Compatibility & System Integration
The MR-J3-700A is compatible with any host controller capable of generating differential or open-collector pulse train output at up to 4 Mpps — Mitsubishi QD75MH4 and QD75D4 MELSEC-Q positioning modules, FX2N-10PG and FX3U-2PG positioning modules for compact PLC systems, and third-party CNC controllers with RS-422A differential pulse output. For parameter configuration and servo tuning, MR Configurator2 connects via USB and provides full access to the MR-J3-700A’s parameter set — the same software used for MR-J4 amplifiers, simplifying maintenance tooling in facilities running both J3 and J4 servo generations. Current-generation HG-SR702 and HG-SR7024 servo motors (MR-J4 standard) can operate with the MR-J3-700A in motor compatibility mode (parameter PA22 = 1) — enabling motor-only upgrades to 22-bit encoder motors while retaining the MR-J3-700A amplifier, or amplifier-only upgrades to MR-J4-700A while retaining the existing HC-series motor. The external safety contactor for the MR-J3-700A must be rated for the motor’s operating parameters — at 37 A continuous and 111 A peak, a safety contactor of at least AC-3 duty class at 37 A and 200 VAC is required, with make current rating verified against the 111 A peak. Refer to Mitsubishi’s MR-J3 safety sub-function manual for approved contactor specifications at the 7 kW power level. The MR-J3-700A’s RS-422 port enables multi-axis parameter cascade connection for simultaneous parameter programming from a single MR Configurator2 USB connection to the first amplifier in the cascade chain — useful during commissioning and maintenance of multi-axis panels with multiple MR-J3-700A units.
Maintenance Tips
The MR-J3-700A at 7 kW generates substantial heat in normal operation — the amplifier’s forced-air cooling fan is the highest-priority mechanical maintenance item. Inspect the cooling fan annually for bearing noise (a high-pitched whine or grinding sound during operation indicates bearing degradation) and replace the fan every 3–4 years regardless of observed condition, as the bearing life at 40°C ambient is approximately 30,000–40,000 hours. A failed cooling fan on the MR-J3-700A generates an overtemperature alarm (AL.46) and emergency stop within minutes of startup, causing significant production downtime — proactive fan replacement during scheduled maintenance prevents this failure mode entirely. The DC bus electrolytic capacitors in the MR-J3-700A have a rated service life of approximately 10 years at 40°C ambient — units approaching 10–12 years of service should be evaluated for proactive replacement or factory refurbishment to avoid capacitor failure during production. Capacitor degradation manifests as increased AL.30 (regenerative overvoltage) sensitivity, unstable DC bus voltage during acceleration, and in advanced cases, visible capacitor top bulging or electrolyte leakage visible through the amplifier’s ventilation openings. The encoder cable (CN2) connecting the MR-J3-700A to the servo motor experiences the highest mechanical stress in servo systems with moving motor mounts — inspect the cable jacket at both ends annually for cracking, and replace cables showing any visible damage even if the amplifier continues to operate intermittently, as a partially failed encoder cable can cause sudden axis runaway.
Frequently Asked Questions
Q: What is the recommended upgrade path from MR-J3-700A to current Mitsubishi servo technology?
A: The direct current-generation upgrade is the MR-J4-700A, providing the same 7 kW power at 200 V with 22-bit encoder resolution (versus 17-bit), built-in STO safety function (eliminating the external safety contactor), AVSC II dual notch filter, and improved auto-tuning. The MR-J4-700A accepts the same HC-SFS702 motor in J3 motor compatibility mode, enabling amplifier-only upgrade without motor replacement. The MR-J4-700A has the same 170 mm housing width and compatible mounting pattern as the MR-J3-700A, simplifying panel retrofit. Use MR Configurator2’s parameter conversion function to create an initial MR-J4-700A parameter set from the existing MR-J3-700A file before the upgrade.
Q: Can the MR-J3-700A be used with an MR-J3-500A on the same multi-axis panel with a shared AC supply?
A: Yes. Multiple MR-J3 amplifiers of different power ratings can share a common three-phase AC supply rail — wire each amplifier’s L1, L2, L3 main circuit terminals individually from the shared supply bus, and size the supply bus, wiring, and circuit protection for the sum of all amplifier rated input currents. For a panel with one MR-J3-700A (approximately 25 A input per phase) and one MR-J3-500A (approximately 17 A input per phase), the combined three-phase input current is approximately 42 A per phase — size the main circuit breaker and supply cabling accordingly, noting that simultaneous full-load operation of both amplifiers is unlikely in normal machine operation.
Q: Does the MR-J3-700A support speed control mode for spindle drive applications?
A: Yes. The MR-J3-700A supports speed control mode via the analogue speed command input (VC terminal, ±10 VDC) or via parameter-configured constant speed mode. In speed control mode, the position loop is disabled and the speed loop regulates motor speed proportional to the analogue command voltage. This mode is used for spindle drive applications, winding tension control, and conveyor speed synchronisation where velocity regulation rather than position accuracy is the primary requirement. The operating mode is selected via amplifier parameter PA01.
Do you need more references from this brand? Explore our full catalog of Mitsubishi here: https://atlantechdrives.com/manufacturers/mitsubishi/
