The MR-J4-15KA is Mitsubishi Electric’s 15 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 74 A for Mitsubishi HG-UR and HG-JR series high-power servo motors — the 15 kW model in the MR-J4-A pulse train input series, designed for large CNC machining centre spindle drives, heavy-duty industrial robot base and shoulder axes, and large-format material handling systems where 15 kW of continuous servo power with pulse train command interface is required. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the MR-J4-15KA?
The MR-J4-15KA is a MELSERVO-J4 series servo amplifier providing 15 kW (15,000 W) continuous output power for Mitsubishi servo motors in the HG-UR15K, HG-JR15K2, and equivalent 15 kW servo motor models. The amplifier accepts position command pulses from a host controller at up to 4 Mpps via differential RS-422A pulse input or 200 kpps via open-collector, interpreting pulse count as position command and pulse frequency as speed command within the standard MR-J4-A pulse train interface architecture. At 74 A continuous output current — significantly higher than the MR-J4-11KA’s 56 A — the MR-J4-15KA’s power stage uses a larger IGBT module and requires correspondingly heavier input power wiring and circuit protection. The amplifier is exclusively rated for three-phase 200–240 VAC supply; single-phase connection is not supported at this power level. All standard MR-J4 features are included: 22-bit multi-turn absolute encoder support, Advanced Vibration Suppression Control II with automated resonance detection, STO safety function compliant with IEC 61800-5-2, and full MR Configurator2 USB connectivity for commissioning, servo tuning, and waveform monitoring. External regenerative resistor connection is required for applications with significant braking energy — no internal regenerative resistor is provided at this power level.
Key Technical Specifications
- Model: MR-J4-15KA
- Rated Output Power: 15 kW (15,000 W)
- Power Supply: 200–240 VAC three-phase only, 50/60 Hz
- Continuous Output Current: 74.0 A
- Maximum Output Current: 222.0 A (3× continuous peak)
- Compatible Servo Motors: HG-UR15K, HG-JR15K2, HG-UR15K4 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: External MR-RB series resistor required
- Communication: USB (MR Configurator2), RS-422 (multi-axis cascade)
- Operating Temperature: 0°C to 55°C (forced air cooling)
- Dimensions (W × H × D): 220 mm × 380 mm × 250 mm
- Weight: Approx. 10.0 kg
Series Comparison & Selection Guide
Within the MR-J4-A 200 V pulse train series, the 11 kW and 15 kW models (MR-J4-11KA and MR-J4-15KA) represent the upper power range — beyond the 22 kW MR-J4-22KA, multi-axis common bus configurations using the MR-J4W-series or dedicated high-power drive systems become the standard architecture. The MR-J4-15KA is the correct selection when the servo motor’s rated current falls in the 56–74 A range at 200 V, or when the application’s continuous torque requirement at the operating duty cycle cannot be met by an 11 kW motor without thermal derating. Common applications specifying the MR-J4-15KA over the MR-J4-11KA include: horizontal machining centre spindle drives where 15 kW spindle power is required for heavy-duty roughing cuts in steel, large-format waterjet cutting gantry axes where the water pump and cutting head combined mass demands higher continuous servo power, and heavy ASRS crane drive systems with rated loads above 2,000 kg. For applications above 15 kW where 22 kW is required, the MR-J4-22KA provides the next power level. For applications where SSCNET III/H network control is preferred over pulse train, the MR-J4-15KB (SSCNET III/H variant) provides identical power with tighter multi-axis synchronisation. The MR-J4-15KA and MR-J4-22KA at 200 V represent the highest practical single-amplifier power levels before the thermal and electrical infrastructure requirements of common bus multi-axis systems become more economical.
Maintenance Tips
The MR-J4-15KA’s forced-air cooling fan is a critical maintenance item at this power level — the amplifier dissipates approximately 400–600 W of heat at full load, and cooling fan degradation directly causes amplifier overtemperature faults and eventual thermal damage. Inspect the cooling fan annually for blade contamination (metal dust, textile fibres, and oil mist are common contaminants in machine tool environments) and measure the fan current draw — a fan drawing more than 20% above its rated current indicates bearing wear approaching end of life. Replace the cooling fan every 3–4 years as a preventive maintenance action regardless of observed condition, as the amplifier’s value and the cost of an unplanned downtime event far exceeds the fan replacement cost. Check the heat sink fin condition during the annual inspection — metal swarf and fibrous contamination accumulate in the heat sink fins, reducing cooling airflow and increasing amplifier operating temperature above the acceptable limit. Clean the heat sink fins with dry compressed air (oil-free) annually. The MR-J4-15KA requires an external regenerative resistor — verify the resistor’s mounting, wiring connections, and thermal condition at the annual inspection. A regenerative resistor with degraded resistance (due to age or thermal damage) can cause the regenerative circuit to become ineffective, causing the DC bus voltage to rise to dangerous levels during motor deceleration. Measure the external resistor’s resistance with a multimeter and compare against the resistor’s rated value — a deviation of more than 10% from the rated resistance indicates resistor degradation requiring replacement.
Frequently Asked Questions
Q: What external regenerative resistor is recommended for the MR-J4-15KA driving a large horizontal machining centre spindle with frequent E-stop events?
A: For a 15 kW spindle with frequent deceleration cycles (such as E-stop from maximum spindle speed), calculate the average regenerative power per deceleration event using the formula: Preg = (0.5 × J × ω²) / t_dec × duty_factor, where J is the total inertia (motor + spindle), ω is the initial angular velocity, t_dec is the deceleration time, and duty_factor is the number of decelerations per second. For typical machining centre spindle E-stop applications, the MR-RB30 (300 W) or MR-RB50 (500 W) external regenerative resistor is appropriate — select the resistor with continuous rated power at least 1.5× the calculated average regenerative power. Install the resistor with adequate ventilation and maintain at least 50 mm clearance around the resistor body to prevent heat accumulation.
Q: Can the MR-J4-15KA be connected in parallel with another MR-J4-15KA to drive a single 30 kW motor?
A: No. Parallel operation of two MR-J4-15KA amplifiers to drive a single motor is not supported by Mitsubishi’s MR-J4 series — the individual amplifiers do not implement current sharing and the interaction between two amplifiers driving the same motor phases would cause control instability and potential amplifier damage. For applications requiring more than 22 kW from a single axis, Mitsubishi’s MR-J4W series common bus multi-axis amplifiers or dedicated high-power drive systems must be specified.
Q: Does the MR-J4-15KA’s STO function comply with EN ISO 13849-1 PLe as well as IEC 61800-5-2 SIL2?
A: Yes. The MR-J4-15KA’s STO function is certified to IEC 61800-5-2 SIL2 and EN ISO 13849-1 PLe (Category 3) — both safety standards applicable to servo drive safe torque-off functions in European machinery safety applications. The dual-channel STO input (STO1 and STO2 on the CN8 connector) achieves the Category 3 / PLe / SIL2 rating when both channels are used independently and the wiring follows the requirements in the MR-J4-15KA safety sub-function instruction manual.
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