AC servo motor
Mitsubishi Electric HK servo motors (MELSERVO-J5)
Rotary servo motors for MELSERVO-J5 from 50 W to 22 kW in ultra-low (HK-MT, HK-RT), low (HK-KT), medium inertia (HK-ST) and heavy-duty (HK-JT) series, with a 26-bit batteryless absolute encoder and up to 10,000 rpm on HK-MT.
Key specifications
| Speed (max) | 10,000 rpm |
|---|---|
| Power | 50–22,000 W |
| Feedback | 26-bit batteryless absolute (67,108,864 pulses/rev) |
| Resolution (max) | 26 bit |
| Sizes | HK-MT 0.05–1 kW; HK-RT 1–7 kW; HK-KT 0.05–2 kW (rated 3,000 rpm); HK-ST 0.5–7 kW (rated 2,000 rpm); HK-JT 7–22 kW |
Summarised in our own words from Mitsubishi Electric Corporation's published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Specify Motion is not affiliated with Mitsubishi Electric Corporation. Mitsubishi Electric and HK servo motors (MELSERVO-J5) are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
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Our experienced engineers are on hand, ready to help with your project. Whether you need the Mitsubishi Electric HK servo motors (MELSERVO-J5) itself, help sourcing it, or a modified or custom design built around your load, speed and space, tell us what the machine has to do and we'll come back with the right option.
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- Complete axis: motor, drive, gearing and feedback matched together
What an AC servo motor is
An AC servo motor is a permanent-magnet synchronous motor designed for closed-loop control of position, speed and torque. A wound stator is driven by a servo drive with sinusoidal three-phase current, while magnets on the rotor follow the rotating field. A high-resolution encoder or resolver on the shaft feeds position back to the drive, which adjusts current many thousands of times a second. The result is precise, dynamic motion with high peak torque, typically about three times the continuous rating for short periods.
When engineers choose an AC servo motor
Choose an AC servo for machine axes needing fast, accurate motion under varying loads, such as packaging, robotics, machine tools and printing. Compared with steppers, servos keep torque at high speed and cannot silently lose position. The trade-offs are cost and set-up: a servo needs a matched drive, feedback and tuning. For simple, low-speed indexing with a steady load, a stepper may be cheaper. For very low speeds and high torque, a gearbox or direct-drive motor may be needed.
How to specify the Mitsubishi Electric HK servo motors (MELSERVO-J5)
Send these with your enquiry and an engineer can confirm the right HK servo motors (MELSERVO-J5) variant or an equivalent:
- Continuous and peak torque (Nm)
- Rated and maximum speed (rpm)
- Load inertia and inertia ratio
- Supply voltage: 230 V single-phase or 400 V three-phase
- Feedback: incremental or absolute encoder, resolution (bits)
- Holding brake, IP code and shaft options
- Flange size and mounting (mm)
Common mistakes to avoid
- Sizing on peak torque without checking RMS torque over the cycle
- Ignoring load-to-motor inertia ratio, which makes tuning hard
- Forgetting the brake is for holding, not dynamic stopping
- Using a motor and drive pair that the supplier has not matched
Mitsubishi Electric HK servo motors (MELSERVO-J5): frequently asked questions
What is the Mitsubishi Electric HK servo motors (MELSERVO-J5)?
Rotary servo motors for MELSERVO-J5 from 50 W to 22 kW in ultra-low (HK-MT, HK-RT), low (HK-KT), medium inertia (HK-ST) and heavy-duty (HK-JT) series, with a 26-bit batteryless absolute encoder and up to 10,000 rpm on HK-MT. Published series figures include speed 10,000 rpm, power 50 W, power 22,000 W, resolution 26 bit. It is made by Mitsubishi Electric Corporation; Specify Motion can help source it or propose an equivalent.
Who makes the Mitsubishi Electric HK servo motors (MELSERVO-J5)?
The Mitsubishi Electric HK servo motors (MELSERVO-J5) is made by Mitsubishi Electric (Mitsubishi Electric Corporation) and is listed here for engineers comparing options. Specify Motion is not affiliated with Mitsubishi Electric Corporation; brand names are used only to identify the product.
What is the speed of the Mitsubishi Electric HK servo motors (MELSERVO-J5)?
The published series maximum speed is 10,000 rpm. Individual models and sizes in the HK servo motors (MELSERVO-J5) range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Mitsubishi Electric HK servo motors (MELSERVO-J5)?
Yes. Our engineers can propose an equivalent built around your load, speed and environment. An engineer confirms the fit against your application before recommending anything.
What is the inertia ratio in servo sizing?
The inertia ratio compares the load inertia reflected to the motor shaft with the motor's rotor inertia. High ratios make the axis harder to tune and slower to settle. Many engineers aim for below about 10:1, and lower for highly dynamic axes, using a gearbox to reduce reflected inertia where needed.
Do AC servo motors need an absolute encoder?
Not always. Incremental encoders need a homing routine after power-up, which is acceptable on many machines. Absolute encoders know their position at power-on, avoiding homing, which saves time and suits robots and multi-axis machines. Multi-turn absolute encoders track turns even when power is off.
Further reading: How to select a servo motor · Servo vs stepper · Servo and stepper motors
Other ac servo motor series
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