Planetary gearbox
Harmonic Drive HPN Harmonic Planetary value series gearbox
A lower-cost inline planetary gearhead range from Harmonic Drive for general servo applications. It has wider backlash limits than HPG.
Key specifications
| Rated torque (max) | 562 Nm |
|---|---|
| Peak torque (max) | 1,265 Nm |
| Speed (max) | 10,000 rpm |
| Ratio | 3–50:1 |
| Backlash (max) | 7 arcmin |
| Sizes | 11, 14, 20, 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 · Source 2
Notes on this data
Backlash is <5 arcmin single-stage and <7 arcmin two-stage. Rated 562 Nm is L10 for size 40. The momentary peak limit is up to 1265 Nm per the LLC tables, but the LLC summary and Harmonic Drive SE give 'peak torque 9–752 Nm' (752 Nm = maximum repeated peak). Some table rows on the LLC page are incomplete. 10000 rpm is size 11 only; other sizes are 6000 rpm. Frame sizes are 42/60/90/115/142 mm. HPN-L and HPN-RA (right-angle) variants are also listed.
Specify Motion is not affiliated with Harmonic Drive SE / Harmonic Drive LLC. Harmonic Drive and HPN Harmonic Planetary value series 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.
High-rigidity Wanshsin inline planetary with three backlash classes down to super-precision, for machine tools, automation and AGVs.
| Published maximum | HPN Harmonic Planetary value series | WSH |
|---|---|---|
| Rated torque | 562 Nm | 2,400 Nm meets or exceeds |
| Peak torque | 1,265 Nm | 7,200 Nm meets or exceeds |
| Ratio (max) | 50:1 | 100:1 meets or exceeds |
| Backlash (lower is better) | 7 arcmin | 1.5 arcmin meets or exceeds |
Wanshsin inline planetary designed for high radial loads, offered in three precision classes.
| Published maximum | HPN Harmonic Planetary value series | WTH |
|---|---|---|
| Rated torque | 562 Nm | 2,050 Nm meets or exceeds |
| Peak torque | 1,265 Nm | 6,150 Nm meets or exceeds |
| Ratio (max) | 50:1 | 100:1 meets or exceeds |
| Backlash (lower is better) | 7 arcmin | 1.5 arcmin meets or exceeds |
Apex Dynamics AGV planetary with a rotating housing so a drive wheel or pulley can mount directly over it; GLS takes shaft input for belt drive.
| Published maximum | HPN Harmonic Planetary value series | GL / GLS |
|---|---|---|
| Rated torque | 562 Nm | — |
| Peak torque | 1,265 Nm | — |
| Ratio (max) | 50:1 | 90:1 meets or exceeds |
| Backlash (lower is better) | 7 arcmin | 3 arcmin meets or exceeds |
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 planetary gearbox is
A planetary gearbox reduces speed and multiplies torque using a central sun gear driven by the motor, several planet gears on a carrier, and an outer ring gear. Load is shared between the planets, so the gearbox is compact, coaxial and torque-dense. A single stage typically gives ratios of about 3:1 to 10:1, and stages are combined for higher ratios. Precision servo planetaries use ground helical or spur gears, preloaded output bearings and a motor adapter flange, with backlash typically a few arcminutes or less.
When engineers choose a planetary gearbox
Choose a planetary gearbox for most servo and stepper axes that need more torque, lower reflected inertia or a better inertia match. It is efficient, typically above 95% per stage, stiff and widely available in standard frames. The trade-offs are backlash, which is low but not zero, and limited single-stage ratio. For zero backlash in a compact joint, a strain-wave gear suits better. For very high shock loads, a cycloidal reducer may be more robust.
How to specify the Harmonic Drive HPN Harmonic Planetary value series
Send these with your enquiry and an engineer can confirm the right HPN Harmonic Planetary value series variant or an equivalent:
- Ratio and output speed (:1, rpm)
- Nominal and peak output torque (Nm)
- Emergency stop torque (Nm)
- Backlash (arcmin) and torsional stiffness (Nm/arcmin)
- Radial and axial output loads (N)
- Motor flange, shaft diameter and length (mm)
- Duty cycle, mounting orientation and lubrication
Common mistakes to avoid
- Sizing on motor torque times ratio without checking acceleration torque and service factors
- Ignoring the input speed limit at high motor speeds
- Mounting a pulley or pinion that overloads the output bearing
- Forgetting the gearbox efficiency and heat in continuous duty
Harmonic Drive HPN Harmonic Planetary value series: frequently asked questions
What is the Harmonic Drive HPN Harmonic Planetary value series?
A lower-cost inline planetary gearhead range from Harmonic Drive for general servo applications. It has wider backlash limits than HPG. Published series figures include rated torque 562 Nm, peak torque 1,265 Nm, speed 10,000 rpm, ratio 3:1. 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 HPN Harmonic Planetary value series?
The Harmonic Drive HPN Harmonic Planetary value series 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 HPN Harmonic Planetary value series?
The published series maximum rated torque is 562 Nm. Individual models and sizes in the HPN Harmonic Planetary value series 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 HPN Harmonic Planetary value series?
Yes. On published figures, Wanshsin WSH and Wanshsin WTH are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
How do I choose a planetary gearbox ratio?
Start from the load speed and motor speed range, then check inertia matching and torque. A ratio that brings the reflected load inertia close to the motor inertia improves dynamics. Then confirm peak output torque during acceleration is within the gearbox rating and that input speed stays under the limit.
What backlash does a precision planetary gearbox have?
Precision servo planetary gearboxes typically have backlash from below one arcminute to several arcminutes, depending on grade and stages. Lower backlash costs more. For most positioning axes, a few arcminutes is fine; for robot joints or optics, strain-wave or zero-backlash designs are used.
Further reading: How to select a planetary gearbox · Harmonic vs planetary vs cycloidal · Gearboxes and harmonic drives
Other planetary gearbox series
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