Torque Motors
Torque Motors / Rotary Direct Drives — torque motors for almost every challenge
Convert electrical energy directly into rotary motion, free of the elasticity, backlash, friction and hysteresis caused by transmission or coupling elements
High torque density, very high speeds, excellent synchronous behavior and low power losses, covering virtually every direct-drive application
High-torque, high-dynamics and high-precision ranges
Torque motors for high torques, high dynamics and high precision
Depending on the application, Schaeffler Industrial Drives offers motor types with different characteristics in torque, speed, synchronism and design. The following four ranges are internal-rotor (or external-rotor) permanent-magnet synchronous torque motors, each optimized for one of four needs: "strong", "fast", "precise" and "special".
RIB
The strong oneInternal-rotor permanent-magnet synchronous · high torque density
RIB is a slotted, permanent-magnet-excited AC synchronous internal-rotor direct-drive motor with a fully potted stator and external liquid cooling. Optimized for maximum efficiency and available torque, it delivers up to 20% more torque or 30% lower power loss than comparable motors, with low torque ripple suited to precise positioning.
Advantages
- High dynamics, high rigidity, compact design
- Maintenance-free, excellent synchronous behavior
- Custom windings reduce energy consumption; downsizing cuts cost
- Higher speed/power achievable through custom design
RKI · RKIB
The fast oneHigh-performance internal rotor · high power density
RKI is a slotted high-performance internal-rotor motor whose redesigned laminated magnet carrier reduces eddy-current losses for higher speed and torque. It offers 7 fixed outer diameters, stators in 25 mm increments, and three magnet versions R10/R12/R22 (high speed/balanced/high torque). Compared with the RI range it achieves up to +30% torque, +400% speed, +400% mechanical performance and −40% thermal loss.
Advantages
- Maximum torque within the available installation space
- Favorable combination of high power output, excellent synchronism and low power loss
- Suited to fast-rotating axes, CNC axes and workpiece spindles
SRV
The precise oneInternal rotor · ultra-precision custom design
SRV is a slotted permanent-magnet internal-rotor direct-drive motor with extremely smooth running, capable of machining premium surfaces with very high form and dimensional accuracy and free of optical defects. With an electrical time constant of just 1/10 it responds quickly, and with ripple-free axial and radial forces it delivers full torque even at low speed, reducing post-processing time and cost.
Advantages
- Highest running smoothness, premium surfaces free of optical defects
- Ripple-free axial/radial forces, excellent synchronism
- Full torque at low speed, very high workpiece form and dimensional accuracy
RE
The special oneExternal rotor · efficient cooling · very high power density
RE is a slotted permanent-magnet external-rotor AC synchronous motor that integrates well into rotary systems and provides higher torque than the RI range within the same installation space. It achieves maximum power density in the smallest installation space, with efficient cooling, compact design and near-maintenance-free operation.
Advantages
- Maximum power density in the smallest space
- High dynamics, high rigidity, efficient cooling
- Synchronism and torque consistency superior to the RI range
- Usable as a direct-drive rotary table or for swivel axes
Ranges for special requirements
Torque motors for special requirements
For special requirements such as large diameters, light weight and exceptionally uniform motion, torque motors with Segment, printed-circuit-board and slotless designs are available.
Segment motors
The variable oneRDDM · large-scale rotary direct drive
Segment motors are custom motors whose primary/secondary parts are designed as segments rather than continuous rings. Segments are easy to manufacture and the torque can be scaled through the number of segments, making even very large diameters economically viable. Magnet height can be adjusted between 25–200 mm in 25 mm increments; the smallest segment generates about 560 N and the largest about 4500 N.
Advantages
- Economical segmented construction makes large motors feasible
- Torque scaled through the number of segments
- Redundant design possible, lower maintenance needs, lower mass
UPR
The lightweight onePrinted circuit board · ironless lightweight
UPR "prints" coils layer by layer using printed-circuit-board material to create an ironless motor that combines high performance, low cost and high energy efficiency. The ironless primary part gives extremely short current rise times (excellent power-to-mass ratio), with no cogging force, very low load ripple, good synchronism, and contact-free, wear-free operation.
Advantages
- Up to 80% higher speed for greater throughput
- High energy efficiency, no cogging, precise positioning without overshoot
- Contact-free and wear-free for high reliability
- Supplied as segments or full rings, low cost
RMF · RMK
The even oneSlotless iron core · exceptionally uniform motion
RMK/RMF are slotless iron-core permanent-magnet AC synchronous motors with an extremely small electrical time constant, high dynamics under control, low attractive force and exceptionally uniform motion. They generate about 2.5–3 N/cm² per unit of effective air-gap area, with high design and diameter flexibility, available in flat or coaxial configurations, suited to medium-torque applications with almost no external force in the direction of motion.
Advantages
- No cogging, exceptionally uniform motion, optimal synchronism
- High flexibility in design and diameter dimensions
- Flat or coaxial design, usable in high-precision applications
RDDS rotary direct drive systems
Rotary Direct Drive Systems — ready-to-use modules integrating motor, bearing, measurement and cooling
Schaeffler Industrial Drives' rotary direct drive systems deliver maximum performance in a small installation space and are available in a range of diameters and heights. They integrate torque motor, precision bearing, integrated measuring system and cooling into a ready-to-install module, eliminating the customer's own integration engineering effort, with high dynamics, high rigidity, smooth running, zero backlash, low-wear maintenance-free operation, a compact structure and easy assembly. Typical applications include positioning rotary tables, test rotary tables, robotic kinematics, automated handling axes, the laser industry and Pick & Place equipment.
RDDS1
Ø130 – 230 mm
Small-diameter rotary subsystem available in 130 / 160 / 180 / 230 mm sizes with options, suited to compact rotary tables and indexing applications.
RDDS1 range matrix →
RDDS2
Ø240 – 565 mm
Medium-to-large-diameter rotary subsystem carrying greater torque and workpieces, suited to large rotary tables, machining and measuring platforms.
RDDS2 range matrix →
RDDS-20-B
Integrated standalone unit
A highly integrated, ready-to-use rotary direct drive unit packaging motor, bearing and measurement into a single module, minimizing installation and setup work.
RDDS-20-B overview →Range comparison table
| Range | Rotor type | Diameter range | Peak torque Tp | Continuous torque (cooled Tcw / uncooled Tc) | Technical documentation |
|---|---|---|---|---|---|
| RIB | Internal rotor | Air gap 89 – 690 mm (8 sizes) | 30 – 13,081 Nm | Cooled 19 – 8,421 Nm Uncooled 7 – 3,613 Nm | RIB matrix → |
| RKI · RKIB | Internal rotor | Outer diameter 230 – 1030 mm | 88 – 17,670 Nm | Cooled 201 – 7,220 Nm Uncooled 88 – 2,568 Nm1 | RKI matrix → |
| RE | External rotor | Outer diameter 230 – 734 mm | 114 – 8,162 Nm | By model | Custom development |
| SRV | Internal rotor | Air gap 89 – 384 mm | By model2 | By model | Custom development |
| RMK · RMF | Slotless iron core | Ø70 – 2500 mm | 2 – 15,000 Nm | By model | Custom development |
| Segment | Segment | Large diameter (> 1260 mm)3 | Up to 182,575 Nm | Cooled up to 135,739 Nm | RDDM → |
| UPR | Printed circuit board | By design | By model4 | By model | Custom development |
| RDDS subsystems | Integrated module | Ø130 – 565 mm | See RDDS matrix | See RDDS matrix | RDDS → |
Tp = peak torque, Tcw = continuous torque (liquid-cooled), Tc = continuous torque (uncooled). The RIB and RKI·RKIB torque figures are taken from the per-model specifications of the on-site RE 1 torque motor catalog; the peak torque for RKI·RE·RMK/RMF is the "peak torque" explicitly stated on the Schaeffler Industrial Drives website; the Segment figures are from the IDAM RDDM catalog. 1 The RKI·RKIB continuous torque (cooled Tcw / uncooled Tc) covers the 230–690 mm size range listed in the RE 1 catalog; the website's peak range extends to larger sizes. 2 The SRV air-gap diameter and maximum speed (89–384 mm, 14,000 rpm) are taken from the website; the website does not publish SRV torque figures. The IDAM RDDM master catalog separately states a HSRV/SRV "torque range 2–6,000 Nm" but does not distinguish peak from continuous, so it is not listed here as peak torque. 3 The Segment design is economically advantageous at diameters > 1260 mm, with a segment tangential force of 560 – 4500 N. 4 UPR is a printed-circuit-board lightweight motor focused on speed (up to 80% higher) and light weight; the website does not promote it via torque figures. The continuous torque for RE, RMK/RMF and SRV is not published on the website and is marked "by model"; actual values vary by model and winding, so please consult our engineering team for selection.
Torque–speed distribution
Continuous torque vs. speed — logarithmic scale, bubble size = diameter
Logarithmic scale; Y = continuous torque, X = speed, bubble size = air-gap diameter. RIB / RKI·RKIB are taken from the per-model figures of the on-site RE 1 catalog (continuous torque Tcw vs. corner speed); RDDS, being a ready-to-use system, uses continuous torque vs. "bearing limit speed" — its speed is primarily limited by the bearing and is defined differently from the electrical speed of a bare motor, so it is shown for relative positioning only. RE / SRV / RMK·RMF / UPR are not included in the scatter plot because the website does not provide per-model torque-speed data.
Suitable for almost every challenge
Applications
Grinding machines
Milling machines
Machining centers
HSC high-speed cutting machines
Tool changers
Milling heads
Gear-cutting machines
Swivel axes
Rotary tables
NC rotary indexing tables
Indexing tables (cyclic)
Workpiece spindles
Presses
Printing machinery
Packaging machinery
Automation technology
High-precision positioning applications
Measuring and inspection machines
Semiconductor production
Electronics assembly
Pick & Place
Medical technology
Collaborative robots (Cobots)
Reflecting telescopes
Textile machinery
The model tags correspond to the application ranges listed for each series on the Schaeffler Industrial Drives website; entries marked "Torque motor range" are general applications for torque motors as a whole. For actual selection, please consult our engineering team based on torque, speed, installation space and precision requirements.
Technical documentation center
Complete technical principles, range matrices and selection data
RIB · RKI · RKIB torque motors
Torque motors overview
Product overview, range characteristics, advantages
Technical principles
Motor characteristic values, thermal protection, electrical connection, cooling, selection
RIB range matrix
RIB11 / 13 / 17 / 19 — specifications for 8 models
RKI / RKIB range matrix
RKI5 and RKIB5 / 11 — specifications for 5 models
Cable outlets
Axial, tangential and radial cable outlet configurations
Segment torque motors
Rotary direct drive systems
Need help with selection?
Our engineering team can help you choose the optimal direct-drive motor solution based on your torque, speed, installation space and precision requirements