The Yaskawa SGM7A-02AFA21 is a compact Sigma-7 (SGM7A) brushless rotary AC servo motor engineered for fast, accurate positioning in low-to-medium power automation axes. Within the Sigma-7 product family, SGM7A is positioned as the general-purpose “workhorse”: a wide-capacity, low-inertia motor line intended to cover most everyday servo applications without forcing a bulky frame size.
This specific model is a 200 V class, 200 W (0.2 kW) motor configured without options (no brake, no shaft seal), using a straight shaft without key, and paired with a 24-bit incremental encoder. That configuration is commonly selected when the machine design favors a clean, clamp-style coupling connection and when absolute-position retention is handled by the system architecture (controller strategy, homing routine, or external reference), rather than by a motor-side absolute encoder.
A design choice that keeps the axis lean: incremental feedback, no extra options
Many servo motors are ordered with brakes, seals, and absolute encoders “just in case.” The SGM7A-02AFA21 is the opposite philosophy: keep the motor simple, efficient, and light, then build the rest of the axis around that reality. Yaskawa lists this model as “without options,” which typically reduces complexity in wiring, mechanical packaging, and maintenance planning.
The encoder choice matters too. This model uses a 24-bit incremental encoder, delivering high-resolution feedback for smooth low-speed behavior and precise positioning—while avoiding the added system requirements that often come with absolute systems (battery packs, batteryless absolute wiring arrangements, or specific recovery workflows). For many machines—especially those with consistent homing cycles, hard stops, external sensors, or routine reference moves—incremental feedback is a cost-effective, dependable approach without sacrificing motion quality.
Dynamic performance: compact motor, high usable torque
In automation, 200 W is often the sweet spot for fast auxiliary axes: feeders, indexing stations, small linear modules, and compact rotary tooling. Yaskawa’s published figures for SGM7A-02AFA21 show a torque and speed envelope designed for that world:
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Rated torque: 0.637 N·m
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Instantaneous maximum torque: 2.23 N·m
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Rated speed: 3000 min⁻¹
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Maximum speed: 6000 min⁻¹
That combination supports short, high-torque bursts for acceleration and disturbance rejection, while keeping a high top speed available for throughput-oriented moves. The motor’s moment of inertia (0.139 × 10⁻⁴ kg·m²) is also published, which is useful for sizing and tuning because it helps you estimate inertia ratios after pulley, belt, or screw reflection. Yaskawa lists an allowable load moment of inertia of 30×, indicating the motor/drive system is intended to tolerate a meaningful range of reflected load inertia when tuned correctly.
Mechanical integration: straight shaft without key for modern couplings
The straight shaft without key configuration is often selected for clamping couplings and compact hub designs where backlash control and easy assembly matter. In practical machine design, this can help standardize assembly procedures: tighten a clamp coupling to a defined torque, verify alignment, and you have a clean torque path without relying on keyways.
Dimensional data supports mechanical planning and retrofits:
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Height: 74.7 mm
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Width: 60 mm
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Depth: 99.5 mm
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Flange dimension (LC): 60 mm
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Flange diameter (LA): 70 mm
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Shaft diameter (S): 14 mm
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Shaft length (Q): 30 mm
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Weight: 0.8 kg
At 0.8 kg, it stays friendly for moving axes, where motor mass directly increases the load on the drive system and reduces achievable acceleration.
Sigma-7 system context: why SGM7A is used so widely
While your part number is a specific motor, it lives inside a broader servo ecosystem: drives (SERVOPACKs), motion controllers, tuning tools, and safety architecture. Yaskawa’s Sigma-7 documentation highlights system-level goals such as high efficiency and low heat generation, paired with 24-bit high-resolution encoder capability and a broad motor lineup (including SGM7A as the low-inertia rotary motor line).
For many OEMs, that matters more than individual motor specs because it affects cabinet density, thermal design, and cycle-time stability across product variants. The “no options” configuration of SGM7A-02AFA21 can be a deliberate standardization choice: fewer unique wiring branches, fewer replacement variants, and less commissioning friction when machines scale.
Typical applications where SGM7A-02AFA21 fits naturally
Because it is 200 W, incremental, no brake, and straight shaft without key, this model commonly fits:
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Horizontal indexing and positioning axes (rotary tables, tool orientation, small transfer modules)
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Compact belt-driven linear stages (fast shuttles, feeders, aligners)
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Packaging and assembly machinery (cut-to-length, sealing modules, part presentation)
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Inspection and test stations (repeatable positioning with high-resolution feedback)
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General automation retrofits where the mechanical envelope is limited and a 200 W class motor is adequate
If the axis must hold load safely during power-off (vertical Z axes, suspended loads), you would normally select a brake-equipped variant instead. This specific model is intentionally not that.
Technical Specifications Table (SGM7A-02AFA21)
| Parameter | Specification |
|---|---|
| Manufacturer | Yaskawa |
| Series / Type | Sigma-7 Rotary Servomotor, SGM7A (low inertia) |
| Model | SGM7A-02AFA21 |
| Input Power Supply | 200 V |
| Rated Output | 0.2 kW (200 W) |
| Rated Torque | 0.637 N·m |
| Instantaneous Maximum Torque | 2.23 N·m |
| Rated Speed | 3000 min⁻¹ |
| Maximum Speed | 6000 min⁻¹ |
| Encoder Resolution | 24-bit |
| Encoder Type | Incremental |
| Shaft End | Straight without key |
| Options | Without options |
| Motor Moment of Inertia | 0.139 × 10⁻⁴ kg·m² |
| Allowable Load Moment of Inertia | 30× |
| Dimensions (H × W × D) | 74.7 × 60 × 99.5 mm |
| Flange (LC / LA) | 60 mm / 70 mm |
| Shaft (Diameter / Length) | 14 mm / 30 mm |
| Weight | 0.8 kg |
Practical integration notes (the stuff that prevents field problems)
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Plan the coupling correctly for a keyless shaft. A clamp coupling is usually the cleanest match. Define assembly torque procedures and verify hub fit so you do not end up with micro-slip during peak torque events.
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Choose incremental feedback intentionally. If the machine needs “power back on and continue exactly where it was,” incremental alone may not match that requirement without additional design measures. If the machine always homes or references on startup, incremental is typically a solid choice.
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Use published inertia data to avoid tuning pain. Match the axis inertia ratio realistically. The motor supports wide ranges (30× allowable load inertia), but smoother machines come from reasonable mechanics: stiff mounts, controlled compliance, and sensible transmission ratios.
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Confirm drive and cable compatibility during BOM lock. Sigma-7 is a system; motor selection, encoder cable type, and drive capacity should be validated together in the final design documentation.
Closing summary
The Yaskawa SGM7A-02AFA21 is a focused, no-excess Sigma-7 rotary servo motor: 200 V, 200 W, 24-bit incremental encoder, straight shaft without key, and no added options. It is a strong fit for compact, high-cycle automation axes where you want Sigma-7 motion quality and responsiveness, but do not need a brake, seal, or absolute feedback scheme. Within the broader Sigma-7 ecosystem, it offers a clean balance of performance, mechanical simplicity, and standardization potential—exactly the kind of motor that quietly makes machines feel fast and consistent day after day.
