The MR-J4-700A is Mitsubishi Electric’s 7 kW MELSERVO-J4 series servo amplifier for three-phase 200 V AC power supply, providing closed-loop servo control at continuous rated output current of 37 A for Mitsubishi HG-SR, HG-RR, and HG-UR series servo motors in the 7 kW frame — the high-end model of the MR-J4-A pulse train input sub-series at 200 V, designed for demanding large-scale machine axes, heavy-load industrial robots, and high-speed gantry systems where 7 kW of continuous servo power with 3× peak torque capability is required. Atlantech Drives holds stock of the MR-J4-700A. Contact us for fast worldwide delivery and competitive pricing.
What Is the MR-J4-700A?
The MR-J4-700A is a MELSERVO-J4 series servo amplifier providing 7 kW (7,000 W) continuous output power — the highest continuous output in the MR-J4-A 200 V single-amplifier range — for Mitsubishi servo motors in the HG-SR702, HG-SR7024, and equivalent 7 kW servo motor models. The amplifier accepts position command pulses from a host controller via open-collector or differential RS-422A pulse input at up to 4 Mpps (differential), interpreting the pulse train as position commands in the same way as all MR-J4-A variants. The three-loop servo control architecture (position, speed, current) operates at a current loop bandwidth of 3.5 kHz — identical to the MR-J4-500A — but with the power stage rated for the higher 37 A continuous current demand of 7 kW motors. The MR-J4-700A requires three-phase 200–240 VAC supply only — unlike the MR-J4-500A which accepts single or three-phase, the MR-J4-700A’s higher power level requires three-phase supply for balanced current draw and is not rated for single-phase operation. The amplifier includes the full MR-J4 feature set: 22-bit multi-turn absolute encoder support, Advanced Vibration Suppression Control II, STO safety function (IEC 61800-5-2), built-in regenerative resistor with external resistor connection capability, and MR Configurator2 USB and RS-422 connectivity for commissioning and monitoring.
Key Technical Specifications
- Model: MR-J4-700A
- 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: HG-SR702, HG-SR7024, HG-RR703, HG-UR703 and equivalent
- 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 22-bit absolute encoder (262,144 pulses/rev)
- Safety Function: STO (Safe Torque Off), IEC 61800-5-2
- Regenerative Brake: Built-in, external MR-RB series resistor connectable
- Communication: USB (MR Configurator2), RS-422 (multi-axis cascade)
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 170 mm × 260 mm × 200 mm
- Weight: Approx. 4.5 kg
Architecture & Design Overview
The MR-J4-700A implements the same three-loop digital servo control architecture as all MR-J4-A series amplifiers, with the power stage scaled for 7 kW continuous output. The amplifier’s IGBT power module uses a three-phase full-bridge inverter topology, converting the rectified 200 VAC DC bus voltage (approximately 280 VDC) into variable frequency, variable voltage three-phase AC for the servo motor windings. The current control loop operates at 3.5 kHz bandwidth, providing rapid torque response to track the position and speed loop commands. The MR-J4-700A’s position loop gain (Kp), speed loop gain (Kvp), and speed loop integration time constant (Ki) are all programmable via MR Configurator2, enabling the servo response characteristics to be tuned for the mechanical system’s inertia, stiffness, and damping. The built-in Advanced Vibration Suppression Control II function implements two independent notch filters whose frequencies are automatically identified by the amplifier’s machine resonance estimation algorithm — the algorithm excites the mechanical system with a swept-frequency signal during a dedicated machine resonance search procedure in MR Configurator2, identifies resonance peaks in the frequency response, and automatically configures the notch filter frequencies to suppress the identified resonances. This automated resonance detection and suppression is particularly valuable for large-scale machine axes where manual identification of mechanical resonance frequencies would require dedicated instrumentation. The MR-J4-700A also implements the Robust Filter function, which adds a second-order low-pass filter to the velocity loop command to attenuate high-frequency noise from encoder differentiation — reducing speed ripple without compromising low-frequency servo bandwidth.
Installation Advice
The MR-J4-700A at 7 kW generates substantial heat during operation — the amplifier’s forced-air cooling fan draws air through the bottom of the unit and exhausts from the top, requiring a minimum 100 mm clearance above the amplifier housing in the control panel for unobstructed hot air exhaust. In densely populated control panels, ensure the MR-J4-700A is not installed below heat-sensitive components (contactors, relays, PLC modules) in the hot air exhaust path. The three-phase 200 VAC input power cables for the MR-J4-700A should be routed separately from the servo motor power cables (U, V, W) — the motor cables carry pulsed voltage waveforms with high dV/dt from the IGBT switching, and the radiated electromagnetic interference from motor cables can induce noise into adjacent control cables including the pulse train command signal. Install the motor power cables in a separate conduit or maintain at least 150 mm physical separation from the command pulse cables. For the pulse train command signal (if using long cable runs from a remote PLC), use differential RS-422A connection rather than open-collector — the MR-J4-700A’s differential input rejects common-mode interference from adjacent motor cables, maintaining reliable pulse reception at up to 4 Mpps even in electrically noisy panel environments where open-collector signals at high pulse frequencies may be compromised.
Frequently Asked Questions
Q: What is the main difference between the MR-J4-500A and the MR-J4-700A in terms of application suitability?
A: The MR-J4-700A provides 40% more continuous output power (7 kW versus 5 kW) and 60% more continuous output current (37 A versus 23 A), enabling it to drive larger servo motors in applications with higher continuous torque requirements. The MR-J4-700A also requires three-phase supply exclusively, while the MR-J4-500A accepts single-phase. In practical terms, specify the MR-J4-700A when the motor’s rated current exceeds 23 A or when the application’s continuous torque requirement cannot be met by a 5 kW motor at the required duty cycle without thermal derating. For most router, engraver, and press brake backstop applications, the MR-J4-500A is adequate; for large-format machining centre main spindles, heavy ASRS crane drives, and high-speed high-load gantry axes, the MR-J4-700A is appropriate.
Q: Can the MR-J4-700A be used in a synchronised multi-axis system with other MR-J4-A amplifiers under a QD75MH positioning module?
A: Yes. The MR-J4-700A’s pulse train input accepts commands from Mitsubishi QD75MH4 or QD75D series positioning modules via differential pulse output — the QD75MH4 manages coordinated multi-axis positioning, generating independent pulse trains for each axis including the MR-J4-700A. For higher performance multi-axis servo systems requiring SSCNET III/H network control, the MR-J4-700B (SSCNET III/H variant of the same power level) should be specified instead of the MR-J4-700A, as SSCNET III/H provides tighter synchronisation and higher command update rates than pulse train input.
Q: Does the MR-J4-700A include a dynamic brake (DB) resistor for controlled motor deceleration on E-stop?
A: The MR-J4-700A includes a built-in dynamic brake circuit that activates on emergency stop (when the servo enable input is deactivated or an alarm occurs), shorting the motor phases through internal braking resistors to decelerate the motor rapidly. The dynamic brake performance depends on the motor speed and load inertia at the moment of E-stop activation — at high speeds with large inertia loads, the braking energy can exceed the built-in DB resistor’s capacity. Mitsubishi’s MR-J4-500A to MR-J4-700A series applications with frequent E-stops at high speed should calculate the average DB energy per stop using the application’s deceleration parameters and verify against the MR-J4-700A’s DB resistor thermal capacity published in the hardware manual.
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