Housed direct-drive motor
NSK Megatorque Motor PB series
Compact Megatorque direct-drive motors with large through holes (φ35 and φ56 mm), 6 to 60 Nm maximum torque and pulse-train control from the EGA driver; ±5 arc-sec repeatability.
Key specifications
| Bore (max) | 56 mm |
|---|---|
| Outer diameter | 102–152 mm |
| Peak torque (max) | 60 Nm |
| Speed (max) | 600 rpm |
| Supply | 200-230 VAC |
| Accuracy | 112 arc-sec |
| Resolution | 524,288 counts/rev |
| Repeatability | ±5 arc-sec |
| Drive | EGA driver (15 or 30 Arms), pulse-train input |
Summarised in our own words from NSK Ltd.'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Notes on this data
Max speed given as 10 and 8 s⁻¹ in the catalogue (600/480 rpm); the table does not map them clearly to models.
Specify Motion is not affiliated with NSK Ltd.. NSK and Megatorque Motor PB 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 NSK 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.
Housed iron-core direct drive rotary motors with bearings and optical encoder, 110-360 mm frames, up to about 1 kNm peak at 600 VDC.
| Published maximum | Megatorque Motor PB series | ADR-A |
|---|---|---|
| Continuous torque | — | 407.2 Nm |
| Peak torque | 60 Nm | 1,017.9 Nm meets or exceeds |
| Speed | 600 rpm | 2,000 rpm meets or exceeds |
Low-profile housed iron-core direct drive motors with large centre holes and incremental encoders, 80-400 mm frames.
| Published maximum | Megatorque Motor PB series | AXD |
|---|---|---|
| Continuous torque | — | 250.6 Nm |
| Peak torque | 60 Nm | 648.9 Nm meets or exceeds |
| Speed | 600 rpm | 3,000 rpm meets or exceeds |
AXD variant with 23-bit BiSS-C absolute encoder resistant to contamination, 120-400 mm frames.
| Published maximum | Megatorque Motor PB series | AXD-ERA |
|---|---|---|
| Continuous torque | — | 250.6 Nm |
| Peak torque | 60 Nm | 648.9 Nm meets or exceeds |
| Speed | 600 rpm | 2,000 rpm 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 housed direct-drive motor is
A housed direct-drive motor is a high-pole-count permanent-magnet torque motor supplied in a complete housing with its own bearings, typically a precision cross-roller or similar bearing, and a high-resolution encoder. The load bolts directly onto the rotor face or shaft, with no gearbox or belt between motor and load. Many designs have a large hollow centre. They are run by a servo drive and provide high torque at low speed with very high stiffness and accuracy.
When engineers choose a housed direct-drive motor
Choose a housed direct-drive motor for rotary tables, indexers and turntables that need high accuracy, fast indexing and no backlash, without the integration effort of a frameless motor. It is ready to mount. The trade-offs are cost and size: direct drive needs a large motor for high torque, and the bearing and encoder are set by the range. Where torque needs are high and accuracy moderate, a servo with a precision gearbox may be cheaper.
How to specify the NSK Megatorque Motor PB series
Send these with your enquiry and an engineer can confirm the right Megatorque Motor PB series variant or an equivalent:
- Continuous and peak torque (Nm)
- Speed (rpm)
- Load inertia and moment load (kgm², Nm)
- Axial and radial load capacity (N)
- Encoder type and resolution
- Through-hole diameter (mm)
- Bus voltage and drive compatibility
Common mistakes to avoid
- Ignoring moment loads from offset tooling
- Mismatching encoder interface and drive
- Overlooking thermal effects on accuracy
- Expecting high torque without a large frame
NSK Megatorque Motor PB series: frequently asked questions
What is the NSK Megatorque Motor PB series?
Compact Megatorque direct-drive motors with large through holes (φ35 and φ56 mm), 6 to 60 Nm maximum torque and pulse-train control from the EGA driver; ±5 arc-sec repeatability. Published series figures include bore 56 mm, outer diameter 102 mm, outer diameter 152 mm, peak torque 60 Nm. It is made by NSK Ltd.; Specify Motion can help source it or propose an equivalent.
Who makes the NSK Megatorque Motor PB series?
The NSK Megatorque Motor PB series is made by NSK (NSK Ltd.) and is listed here for engineers comparing options. Specify Motion is not affiliated with NSK Ltd.; brand names are used only to identify the product.
What is the bore of the NSK Megatorque Motor PB series?
The published series maximum bore is 56 mm. Individual models and sizes in the Megatorque Motor PB 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 NSK Megatorque Motor PB series?
Yes. On published figures, Akribis Systems ADR-A and Akribis Systems AXD are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
When should I choose a direct-drive rotary table instead of a geared one?
Choose direct drive when you need high accuracy, fast settling, no backlash and low maintenance, especially for indexing and inspection. Choose a geared solution where torque requirements are high and cost must be controlled. Direct-drive motors are larger for the same torque.
Do housed direct-drive motors need a brake?
Not always. Horizontal tables often hold position under servo control. Vertical axes, unbalanced loads or safety requirements may need a brake or clamp. The machine's risk assessment determines whether a holding brake or clamp is required, and brake or clamp options vary between ranges, so confirm availability early in the design.
Further reading: How to select a frameless torque motor · Frameless and torque motors
Other housed direct-drive motor series
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