Harmonic actuator
Harmonic Drive SHA-CG hollow-shaft servo actuators
A hollow-shaft servo actuator variant using CSG-based gearing. It is available in 200 VAC and low-voltage 48 VDC versions in the smaller sizes.
Key specifications
| Rated torque (max) | 382 Nm |
|---|---|
| Peak torque (max) | 841 Nm |
| Speed (max) | 120 rpm |
| Supply | 200 VAC (100 VAC size 25; 48 VDC / 20–90 VDC sizes 20/25/32) |
| Ratio | 50–160:1 |
| Sizes | 20, 25, 32, 40 |
Summarised in our own words from Harmonic Drive SE / Harmonic Drive LLC's published data; series maxima, individual models vary. Last checked 2026-10-29. Source 1
Notes on this data
Maxima: max torque 841 Nm (size 40, 160:1) and continuous torque 382 Nm (size 40 with HA-800 24D drive). 120 rpm is size 20 at 50:1 (200 VAC). Positioning accuracy is 30–60 arcsec and surface runout <10 µm. The page gives no bore, IP or numeric backlash figure.
Specify Motion is not affiliated with Harmonic Drive SE / Harmonic Drive LLC. Harmonic Drive and SHA-CG hollow-shaft servo actuators are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Harmonic Drive 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.
Hollow-shaft harmonic servo actuator: strain-wave gearing, motor, encoder and brake in one unit, run from a separate servo drive. Six frame sizes, from 48 VDC to 220 VAC.
| Published maximum | SHA-CG hollow-shaft servo actuators | MAH |
|---|---|---|
| Peak torque | 841 Nm | 800 Nm |
| Rated torque | 382 Nm | 557 Nm meets or exceeds |
| Speed | 120 rpm | 125 rpm meets or exceeds |
Large-bore version of the harmonic actuator with a frameless 16-pole motor, giving a much bigger through-hole for cabling. Two sizes.
| Published maximum | SHA-CG hollow-shaft servo actuators | MAT |
|---|---|---|
| Peak torque | 841 Nm | 800 Nm |
| Rated torque | 382 Nm | 557 Nm meets or exceeds |
| Speed | 120 rpm | 102 rpm |
Compact robot-joint harmonic actuator with built-in EtherCAT/CANopen drive, dual 20-bit encoders and optional torque sensor, from 0.35 kg; aimed at humanoids and cobots.
| Published maximum | SHA-CG hollow-shaft servo actuators | MGU |
|---|---|---|
| Peak torque | 841 Nm | 762 Nm |
| Rated torque | 382 Nm | 557 Nm meets or exceeds |
| Speed | 120 rpm | 68 rpm |
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 a harmonic actuator is
A harmonic actuator is a rotary servo actuator that combines a strain-wave gear, a servo motor, a position encoder and often a brake in one compact housing. Many have a hollow shaft for cables, and some include the servo drive with a fieldbus interface. The strain-wave gear gives a high ratio with near-zero backlash, while a precision output bearing carries the load directly. The actuator is ready to mount as a robot joint or precision rotary axis.
When engineers choose a harmonic actuator
Choose a harmonic actuator for robot joints, positioners and precision rotary axes where compact size, zero backlash and fast integration matter. It saves the design effort of combining motor, gear, encoder and bearings. The trade-offs are cost and flexibility: the motor, gear ratio and feedback are fixed by the range, and torque limits are set by the strain-wave gear. For heavy shock loads, a cycloidal solution may be more robust.
How to specify the Harmonic Drive SHA-CG hollow-shaft servo actuators
Send these with your enquiry and an engineer can confirm the right SHA-CG hollow-shaft servo actuators variant or an equivalent:
- Rated and peak output torque (Nm)
- Output speed (rpm)
- Ratio (:1)
- Hollow shaft diameter (mm)
- Feedback: motor-side and output-side encoders
- Brake and integrated drive options
- Supply voltage and interface
Common mistakes to avoid
- Exceeding momentary torque in a collision
- Ignoring output bearing moment load
- Mismatching drive and encoder interface
- Forgetting heat in continuous duty
Harmonic Drive SHA-CG hollow-shaft servo actuators: frequently asked questions
What is the Harmonic Drive SHA-CG hollow-shaft servo actuators?
A hollow-shaft servo actuator variant using CSG-based gearing. It is available in 200 VAC and low-voltage 48 VDC versions in the smaller sizes. Published series figures include rated torque 382 Nm, peak torque 841 Nm, speed 120 rpm, ratio 50:1. It is made by Harmonic Drive SE / Harmonic Drive LLC; Specify Motion can help source it or propose an equivalent.
Who makes the Harmonic Drive SHA-CG hollow-shaft servo actuators?
The Harmonic Drive SHA-CG hollow-shaft servo actuators is made by Harmonic Drive (Harmonic Drive SE / Harmonic Drive LLC) and is listed here for engineers comparing options. Specify Motion is not affiliated with Harmonic Drive SE / Harmonic Drive LLC; brand names are used only to identify the product.
What is the rated torque of the Harmonic Drive SHA-CG hollow-shaft servo actuators?
The published series maximum rated torque is 382 Nm. Individual models and sizes in the SHA-CG hollow-shaft servo actuators 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 Harmonic Drive SHA-CG hollow-shaft servo actuators?
Yes. On published figures, MAH and MAT are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
What is the benefit of dual encoders on a harmonic actuator?
A motor-side encoder controls the motor, while an output-side encoder measures the joint position directly after the gear. This compensates for gear deflection and gives true absolute output position at power-up. Dual encoders improve accuracy and support safety and collision detection.
Can a harmonic actuator include its own drive?
Yes, some versions integrate the servo drive and communicate over EtherCAT, CANopen or similar networks. This reduces cabinet space and wiring. Other versions connect to a separate servo drive. Choose by machine architecture, cabinet space and the safety functions needed, such as safe torque off or functional safety over the network.
Further reading: How to select a harmonic actuator · Harmonic vs planetary vs cycloidal · Gearboxes and harmonic drives
Other harmonic actuator series
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