The Yaskawa SGM7A-08A6A21 is a Sigma-7 (SGM7A) rotary AC servo motor built for high-response motion axes where cycle time, accuracy, and reliability all matter at once. It sits in the widely used “general-purpose, low-inertia” class of Sigma-7 rotary servomotors, aimed at machines that need fast acceleration and stable settling without moving up to a larger inertia motor family.
This model is specified for a 200 V input system and delivers 0.75 kW rated output, making it a practical choice for mid-size axes such as indexing tables, compact belt/screw stages, pick-and-place modules, carton/label handling units, and many types of automated assembly equipment. In real production environments, this power class often hits a sweet spot: enough continuous torque to stay thermally comfortable under repetitive duty cycles, while still compact enough to keep machine mechanics light and responsive.
Performance profile: 0.75 kW with strong torque headroom
From a motion design standpoint, SGM7A-08A6A21 is attractive because its numbers support both “push” and “snap”:
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Rated torque: 2.39 N·m
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Instantaneous maximum torque: 8.36 N·m
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Rated speed: 3000 min⁻¹
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Maximum speed: 6000 min⁻¹
That peak-to-rated torque margin is what helps an axis punch through acceleration ramps, short dwell times, or transient disturbances without either oversizing the motor or accepting sluggish motion. It also gives extra tuning room: you can bias the system for smoothness and still keep adequate peak capability for real-world load variation.
Another spec that quietly drives system behavior is inertia. The motor moment of inertia is 0.776 × 10⁻⁴ kg·m², and the product page lists an allowable load moment of inertia of 20 times. Together, these figures matter for servo stability, resonance sensitivity, and how aggressively you can tune without exciting the mechanics. In practical terms: a low-inertia motor like the SGM7A line is often chosen specifically to improve responsiveness and shorten settle time on well-designed, stiff mechanisms.
Batteryless absolute encoder: less maintenance, cleaner restarts
SGM7A-08A6A21 includes a 24-bit encoder and is specified as batteryless absolute. Absolute feedback is valued because it supports position retention and reduces the need for homing routines after power cycles. The “batteryless” part matters because it reduces a classic operational annoyance: encoder battery maintenance.
Yaskawa describes the motivation and underlying idea behind batteryless encoder technology in its encoder technology overview: conventional absolute encoders often use a battery to maintain operation/state when power is off, which introduces maintenance and cost; batteryless technology is developed to detect multiple revolutions without batteries and store that data in non-volatile memory even when power is off. This is exactly the kind of feature that doesn’t change your machine’s headline performance, but does improve uptime behavior and long-term service simplicity.
Mechanical integration: compact 80 mm flange class and keyless shaft
Mechanically, SGM7A-08A6A21 is designed for straightforward coupling and dense packaging in modern machine frames:
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Shaft end: straight, without key
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Shaft diameter / length: 19 mm / 40 mm
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Flange dimension / diameter: 80 mm / 90 mm
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Dimensions (H × W × D): 94.7 × 80 × 145 mm
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Weight: 2.3 kg
A keyless shaft is commonly paired with clamp-style couplings or high-precision hubs. The advantage is clean assembly and strong concentricity potential; the engineering trade is that coupling selection, tightening method, and alignment discipline become especially important for repeatable servo behavior at high acceleration.
This specific configuration is also listed as “without options.” That typically implies no holding brake and no additional sealing options in this model code, which is ideal for horizontal axes and many rotary applications, while vertical axes may require a brake-equipped variant depending on the safety concept.
Efficiency and heat behavior: practical cabinet-level advantages
Servo systems rarely fail because they lack peak torque on paper; they fail because heat and duty cycles punish weak designs. Sigma-7 materials emphasize high efficiency and low heat generation as a core characteristic of the platform. In the Sigma-7 brochure, Yaskawa states that improved motor efficiency can reduce heat generation by about 20% (general Sigma-7 claim).
Lower heat helps in three ways that production teams actually feel:
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More stable performance over long shifts (less thermal drift).
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Less stress on nearby components in tight enclosures.
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More flexibility in cabinet layout and cooling design.
Commissioning and system usability with Sigma-7 drives
While the motor is only one part of the axis, Sigma-7 was developed as a system with strong emphasis on commissioning speed and reliable throughput. The Sigma-7 brochure highlights simplified commissioning support, including functions intended to reduce tuning complexity and speed setup. If you are building standardized machine platforms or doing multi-axis rollouts, that kind of “time-to-stable-motion” improvement can be as valuable as raw torque.
On the product page for SGM7A-08A6A21, Yaskawa also lists related Sigma-7 servo amplifiers such as SGD7S single-axis SERVOPACKs and SGD7W dual-axis SERVOPACKs, as well as SGD7C variants with built-in controller. This is useful when you want a clean, family-consistent servo stack and standardize spares and software tools across machines.
Typical applications where this motor makes sense
Based on the Sigma-7 positioning and the 0.75 kW / low-inertia profile, SGM7A-08A6A21 is a good match for:
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High-speed packaging modules and synchronized motion sections
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Semiconductor handling and precision manufacturing equipment (where repeatability and smooth motion matter)
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Printing, converting, and web-handling subsystems requiring tight speed and position regulation
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General industrial automation axes that need compact size, high response, and reduced maintenance overhead
Technical Specifications (SGM7A-08A6A21)
| Item | Specification |
|---|---|
| Manufacturer / Series | Yaskawa Sigma-7, SGM7A Rotary Servomotor |
| Model | SGM7A-08A6A21 |
| Input power supply | 200 V |
| Rated output | 0.75 kW |
| Rated torque | 2.39 N·m |
| Instantaneous maximum torque | 8.36 N·m |
| Rated speed | 3000 min⁻¹ |
| Maximum speed | 6000 min⁻¹ |
| Encoder resolution | 24-bit |
| Encoder type | Batteryless absolute |
| Motor moment of inertia | 0.776 × 10⁻⁴ kg·m² |
| Allowable load moment of inertia | 20 times |
| Shaft end | Straight without key |
| Shaft diameter / length | 19 mm / 40 mm |
| Flange dimension / diameter | 80 mm / 90 mm |
| Dimensions (H × W × D) | 94.7 × 80 × 145 mm |
| Weight | 2.3 kg |
| Options | Without options |
Summary
The Yaskawa SGM7A-08A6A21 is a compact 0.75 kW, 200 V Sigma-7 rotary servo motor that combines low inertia, high peak torque, and a 24-bit batteryless absolute encoder in an 80 mm flange class mechanical package. For machine builders and maintenance teams, it delivers a practical blend of fast motion response, predictable servo tuning behavior, and reduced battery-related service friction—especially when deployed as part of a standardized Sigma-7 servo system.
