AC servo motor
Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) AC servo motor
Yaskawa's established AC servo motor generation with 24-bit encoders, covering low-inertia, medium-inertia and high-torque families from 200 W to 15 kW on 400 V.
Key specifications
| Rated torque (max) | 22.3 Nm |
|---|---|
| Peak torque (max) | 54 Nm |
| Speed (max) | 6,000 rpm |
| Power (max) | 15,000 W |
| Supply | 400 Vac class (200 V class also offered) |
| Feedback | 24-bit absolute or incremental encoder |
Summarised in our own words from Yaskawa Electric Corporation's published data; series maxima, individual models vary. Last checked 2026-10-29. Source 1
Notes on this data
From Sigma-7 400 V catalogue (German edition): SGM7J 0.2-1.5 kW, 0.637-4.77 Nm rated, 14.3 Nm peak; SGM7A 0.2-7 kW, up to 22.3 Nm rated, 54 Nm peak; SGM7G 450 W-15 kW at 1500 rpm but its torque figures were not in the extract, so torque maxima understate SGM7G. 200 V catalogue not read. Status current, though Sigma-X is the newer generation.
Specify Motion is not affiliated with Yaskawa Electric Corporation. Yaskawa and Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) model codes
Published model codes in the Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) range, with key figures from the manufacturer's data. Search this page for your part number, or send it to us for availability or an equivalent.
| Model code | Rated output (W) | Rated torque (Nm) | Description |
|---|---|---|---|
| SGM7J-02D | 200 | 0.637 | 400 V class |
| SGM7J-04D | 400 | 1.27 | 400 V class |
| SGM7J-08D | 750 | 2.39 | 400 V class |
| SGM7J-15D | 1500 | 4.77 | 400 V class |
| SGM7A-02D | 200 | 0.637 | 400 V class |
| SGM7A-04D | 400 | 1.27 | 400 V class |
| SGM7A-08D | 750 | 2.39 | 400 V class |
| SGM7A-10D | 1000 | 3.18 | 400 V class |
| SGM7A-15D | 1500 | 4.9 | 400 V class |
| SGM7A-20D | 2000 | 6.36 | 400 V class |
| SGM7A-25D | 2500 | 7.96 | 400 V class |
| SGM7A-30D | 3000 | 9.8 | 400 V class |
| SGM7A-40D | 4000 | 12.6 | 400 V class |
| SGM7A-50D | 5000 | 15.8 | 400 V class |
| SGM7A-70D | 7000 | 22.3 | 400 V class |
| SGM7G-05D | 450 | — | 400 V class |
| SGM7G-09D | 850 | — | 400 V class |
| SGM7G-13D | 1300 | — | 400 V class |
| SGM7G-20D | 1800 | — | 400 V class |
| SGM7G-30D | 2900 | — | 400 V class |
| SGM7G-44D | 4400 | — | 400 V class |
| SGM7G-55D | 5500 | — | 400 V class |
| SGM7G-75D | 7500 | — | 400 V class |
| SGM7G-1AD | 11000 | — | 400 V class |
| SGM7G-1ED | 15000 | — | 400 V class |
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Yaskawa part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Kinco's current-generation AC servo motor line, matched to the JD2 and FD5P PRO drives. Small-inertia 40-80 mm frames run at 3000 rpm on 220 V; large-inertia 130 and 180 mm frames are 1500 rpm machines reaching 47.8 Nm rated and 7.5 kW, with 23-bit multi-turn absolute encoders as standard.
| Published maximum | Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) | SMK Series AC Servo Motors (SMK40S/60S… |
|---|---|---|
| Rated torque | 22.3 Nm | 47.8 Nm meets or exceeds |
| Peak torque | 54 Nm | 119.5 Nm meets or exceeds |
| Speed | 6,000 rpm | 6,000 rpm meets or exceeds |
| Power | 15,000 W | 7,500 W |
Kinco's established AC servo motor range from 40 to 180 mm frames, covering 50 W to 7.5 kW and up to 48 Nm rated torque. Standard feedback is a 2500-line incremental encoder with Hall commutation, with absolute options and a resolver on the 180 mm frame. Pairs with FD2S and CD2S drives.
| Published maximum | Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) | SMH Series AC Servo Motors (SMH40S-SMH… |
|---|---|---|
| Rated torque | 22.3 Nm | 48 Nm meets or exceeds |
| Peak torque | 54 Nm | — |
| Speed | 6,000 rpm | — |
| Power | 15,000 W | 7,500 W |
A complete AGV drive wheel combining servo motor, drive, reducer, brake and polyurethane tyre in one unit on 24-60 VDC with CANopen. Three published sizes (150, 165 and 180 mm wheels) give 3.6-40 Nm rated and up to 99 Nm peak at the wheel, for mobile robots carrying up to 1 tonne.
| Published maximum | Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) | iWMC Integrated Servo Wheel |
|---|---|---|
| Rated torque | 22.3 Nm | 40 Nm meets or exceeds |
| Peak torque | 54 Nm | 99 Nm meets or exceeds |
| Speed | 6,000 rpm | — |
| Power | 15,000 W | — |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
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 Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G)
Send these with your enquiry and an engineer can confirm the right Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) 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
Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G): frequently asked questions
What is the Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G)?
Yaskawa's established AC servo motor generation with 24-bit encoders, covering low-inertia, medium-inertia and high-torque families from 200 W to 15 kW on 400 V. Published series figures include rated torque 22.3 Nm, peak torque 54 Nm, speed 6,000 rpm, power 15,000 W. It is made by Yaskawa Electric Corporation; Specify Motion can help source it or propose an equivalent.
Who makes the Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G)?
The Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) is made by Yaskawa (Yaskawa Electric Corporation) and is listed here for engineers comparing options. Specify Motion is not affiliated with Yaskawa Electric Corporation; brand names are used only to identify the product.
What model codes are in the Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) range?
The Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) range includes SGM7J-02D, SGM7J-04D, SGM7J-08D, SGM7J-15D, SGM7A-02D, SGM7A-04D, SGM7A-08D, SGM7A-10D and 17 more. The table on this page lists each published model code with its key figures. Send us the code you use, or the one you need to replace, and our engineers will confirm availability, lead time or the closest equivalent.
What is the rated torque of the Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G)?
The published series maximum rated torque is 22.3 Nm. Individual models and sizes in the Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G) 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 Yaskawa Sigma-7 rotary servomotors (SGM7J / SGM7A / SGM7G)?
Yes. On published figures, Kinco SMK Series AC Servo Motors (SMK40S/60S/80S, SMK130G, SMK180G) and Kinco SMH Series AC Servo Motors (SMH40S-SMH180D) are the closest match from our supply network. 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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