Magnetic bearing systems: selection & comparison limits
A magnetic bearing is part of a rotor support and control system, not a simple size replacement for a ball bearing.
On this page5 sections ⌄
Active magnetic bearings: control, backup support and real applications
A magnetic bearing uses magnetic force to support a rotor. The active systems described here are an integrated bearing, sensing and control arrangement, not a drop-in size substitute for a ball bearing. Passive and superconducting designs need different evidence and are not treated as the same construction.
How does an active magnetic bearing work?
An active magnetic bearing (AMB) uses electromagnets to apply supporting forces while position sensors report rotor movement. A controller adjusts coil current to keep the shaft within its intended position range. Radial control acts across the shaft; axial control manages motion along its axis. The normal operating support is noncontact and does not need an oil film at that interface.
| System element | Function | Information to retain |
|---|---|---|
| Radial / axial magnetic supports | Apply controlled forces to the rotor | Geometry, load direction and operating envelope |
| Position sensors | Measure rotor displacement | Location, reference position and calibration |
| Controller / amplifiers | Turn feedback into coil current | Matched hardware, firmware and validated settings |
| Backup support | Limit motion when levitation is unavailable | Touchdown conditions and inspection criteria |
On a small screen, scroll the table horizontally.
A permanent-magnet motor describes the drive. It does not mean its bearings are passive permanent-magnet bearings.
Reference basis: SKF MT/P2 16509 EN, March 2016, pp. 3–5; SKF Evolution, magnetic bearings in wastewater blowers, 2014. Reviewed 2026-10-02.
What happens when power or levitation is lost?
The answer depends on the complete system. Danfoss's Turbocor engineering brochure describes touchdown bearings that support an unenergized rotor and limit unwanted contact. It also describes conversion of mechanical energy back to electrical energy during a power failure to enable a controlled de-levitation and shutdown. Do not assume every AMB uses that scheme.
SKF's published blower example similarly combines auxiliary ball bearings with backup power and a controlled coast-down. A touchdown bearing is not intended to be selected solely by the diameter of the magnetic-bearing air gap.
- Identify the exact compressor, rotor and control-system configuration before interpreting an alarm.
- Use the equipment's shutdown and lockout procedure; do not bypass position, vibration or current protection.
- Retain the fault log, speed and touchdown history for the prescribed inspection. A stopped rotor does not by itself prove that the support is undamaged.
This reference does not provide controller tuning, a restart authorization or a generic backup-bearing replacement number.
Reference basis: Danfoss Turbocor engineering brochure, p. 5; SKF Evolution, magnetic bearings in wastewater blowers, 2014. Reviewed 2026-10-02.
SKF S2M and E300V2: distinguish the bearing system from its controller
SKF's March 2016 publication MT/P2 16509 EN documents S2M magnetic-bearing applications in gas compressors, turboexpanders and power-generation equipment. E300V2 names a controller platform in that publication, not an interchangeable rolling-bearing model.
Use the machine-specific bearing assembly, sensor, controller and rotor documentation together. This historical source establishes technology and application examples; it does not establish present availability, a complete S2M product range or compatibility with another compressor.
No common d×D×B number, ABEC class or rolling-bearing dynamic rating has been invented for these custom systems.
Reference basis: SKF MT/P2 16509 EN, March 2016, pp. 3–5. Reviewed 2026-10-02.
Magnetic-bearing chillers and Danfoss Turbocor compressors
Danfoss Turbocor centrifugal compressors combine magnetic bearing support, a permanent-magnet motor and variable-speed operation. The technology is used in air-cooled, water-cooled and evaporatively cooled chiller arrangements. The word air-cooled refers to the cooling arrangement; it does not make the rotor support an air bearing.
Compare the exact compressor variant, refrigerant, electrical supply, operating envelope and chiller controls before considering any replacement. The compressor and complete chiller are different assembly levels; a compressor name is not a loose bearing part number.
An oil-free bearing interface does not mean the full machine requires no inspection. No universal efficiency percentage, service interval or chiller-to-chiller interchange is asserted here.
Reference basis: Danfoss Turbocor technology overview; Danfoss Turbocor engineering brochure, p. 5. Reviewed 2026-10-02.
Blowers, motors and high-speed applications
SKF's 2014 wastewater-treatment example describes magnetic-bearing permanent-magnet motors for blowers, with bearing cartridges, displacement sensors, temperature monitoring and auxiliary bearings. It is a documented machine architecture, not evidence that every high-speed motor or fan has an AMB.
For a blower or compressor comparison, record the rotor's operating-speed range, imposed loads, process conditions, cooling and control system. A nominal motor-power figure alone does not establish magnetic-bearing load capability. Product advertising such as magnetic fan bearing must be checked against the actual support architecture before applying AMB conclusions.
Ball-pass frequency formulas describe rolling contacts; they are not AMB control-loop frequencies.
Reference basis: SKF Evolution, magnetic bearings in wastewater blowers, 2014. Reviewed 2026-10-02.
Selection record: what is known and what remains missing?
BearingScope currently has no validated complete magnetic-bearing model database. Passive permanent-magnet arrangements, superconducting designs, homopolar layouts and named chiller service manuals remain separate data needs. They are not answered by labeling an active-system overview as a complete design guide.
| Question | Required evidence | Not a substitute |
|---|---|---|
| Will it support the rotor? | Validated radial/axial loads and rotor operating conditions | Shaft diameter alone |
| Will it remain stable? | Rotor/control assessment across start, running and stop | A ball-bearing speed rating |
| Can it survive loss of support? | Machine-specific energy reserve and touchdown design | An assumed generic UPS or backup bearing |
| Is the replacement compatible? | Matched assembly, controller, sensors and approved machine documentation | A cross-brand dimensional candidate |
On a small screen, scroll the table horizontally.
Reference basis: SKF MT/P2 16509 EN, March 2016, pp. 3–5; Danfoss Turbocor engineering brochure, p. 5. Reviewed 2026-10-02.
Original BearingScope explanations based on public manufacturer technical references. Model values retain their stated units and conditions. This website does not sell, certify or approve substitutions.
What to check
Define rotor and control requirements
Record rotor dynamics, load, speed, displacement limits, sensors, power and control architecture.
Plan abnormal conditions
Backup or touchdown bearings and power-loss behaviour need their own verification. Do not use a generic cross-reference result to specify them.
Data availability
This catalogue does not contain validated complete magnetic-bearing systems. The absence is stated explicitly rather than filling the page with unrelated rolling-bearing models.
Continue with real catalogue data
Preserve the full model, source description and unknown fields when making your shortlist. This reference website does not sell bearings or certify a replacement.
Related questions and tools
Miniature & small ball bearings
Small size does not remove the need to specify load, closure and mounting tolerances.
Read and apply →Thin-section & thin-wall bearing selection
A small cross section is a design characteristic, not a statement that every thin bearing is interchangeable.
Read and apply →Flanged bearings: ring flanges vs flanged housing units
A flange on a miniature bearing ring is not the same component as a two-bolt or four-bolt flanged housing.
Read and apply →Ceramic, hybrid & steel bearing selection
Separate rolling-element material from ring material and the complete bearing construction.
Read and apply →Stainless & corrosion-resistant bearing selection
A stainless label does not establish compatibility with every chemical, washdown or marine exposure.
Read and apply →Air & gas bearings: selection requirements and data limits
Air-film systems are not ordinary rolling bearings with an interchangeable part number.
Read and apply →Hydrodynamic journal bearings & plain-bearing selection
A journal-bearing system depends on the sliding geometry and lubricant film, not a rolling-bearing L10 calculation alone.
Read and apply →Reference basis & data limits
Manufacturer terminology is retained in the product records. Technical reference basis: JTEKT Basic Bearing Knowledge (boundary dimensions, tolerance classes and lubrication); NSK Bearing ABCs (lubrication, designations and clearance); NTN technical FAQs (closure codes and component interchange); SKF rolling-bearing selection and maintenance references.
Selection workflows and catalogue grouping are BearingScope editorial aids. Verify the current drawing and application requirements before using a candidate. Missing database information is not converted into an assumed match.