Electromagnetic actuators
Laminated poles and coils generate attractive force. Pole count, air gap, current, saturation, heat, and force linearization shape capacity.
Magnetic bearings · active rotor control
Levitation is a controls problem.
Active magnetic bearings combine electromagnets, displacement sensors, power electronics, control software, rotor dynamics, and auxiliary bearings into one support system.
Normal operationNon-contact rotor support
Control loopSense · compute · actuate
Key capabilityActive stiffness + damping
ProtectionTouchdown bearings
01 / System architecture
The bearing extends from steel to software.
An active magnetic bearing stabilizes a rotor by continuously correcting its position. The mechanical, electromagnetic, sensing, power, and control designs have to close together.
Position sensors
Eddy-current, inductive, capacitive, optical, or other sensors measure rotor displacement with bandwidth and noise appropriate to the control loop.
Controller + amplifiers
Control laws turn measured displacement into coil current while managing stability, vibration modes, saturation, faults, and machine protection.
Touchdown bearings
Rolling, dry-running, or specialty auxiliary bearings catch the rotor during a loss of levitation and absorb a limited number of demanding events.
Permanent magnets can bias force and reduce steady current, but passive magnetic support alone faces stability constraints. Most industrial high-performance systems use active control on the necessary axes and a defined strategy for axial load, disturbance rejection, and shutdown.
02 / Why magnetic
Non-contact support changes what can be controlled.
| Capability | What it means | System implication |
|---|---|---|
| High-speed operation | No rolling-element centrifugal load or steady contact at the support. | Rotor stress, windage, motor, containment, and critical speeds still limit the machine. |
| Active vibration control | Controller can shape effective stiffness and damping within bandwidth and force limits. | Rotor model, sensor placement, latency, filters, and commissioning become critical. |
| Clean or vacuum service | No bearing lubricant is required in the normal magnetic gap. | Outgassing, cooling, touchdown materials, and motor or process contamination still matter. |
| Condition data | Position, current, orbit, and controller signals expose rotor behavior. | Data quality, storage, alarm logic, and interpretation should be designed in. |
| Adjustable rotor center | Setpoint can sometimes compensate alignment, load, or thermal changes. | Available force, clearance, seal geometry, and protection logic constrain adjustment. |
03 / Specification
Start with the rotor, fault cases, and control objective.
- Rotor model
- Mass distribution, inertia, operating speed range, critical speeds, flexible modes, imbalance, process forces, and gyroscopic effects.
- Force envelope
- Steady load, transient load, unbalance force, shock, axial thrust, required control margin, and electromagnetic saturation.
- Air gap + clearance
- Nominal magnetic gap, seal gaps, motor gaps, touchdown clearance, thermal growth, runout, and assembly tolerance.
- Control performance
- Bandwidth, damping, orbit limits, vibration targets, sensor noise, latency, sampling, commissioning, and machine-state logic.
- Thermal system
- Coil loss, eddy currents, windage, electronics, cooling path, ambient conditions, and process heat.
- Fault response
- Power loss, sensor loss, amplifier fault, overload, overspeed, process upset, emergency shutdown, and restart inspection.
Touchdown events are part of the design
The auxiliary bearing is not an afterthought. Clearance, rotor drop energy, speed, whirl, contact duration, material, cage behavior, lubrication, heat, rebound, and event count determine whether the system survives a fault without secondary damage.
Have a rotor model or a legacy magnetic-bearing system?Open a magnetic-bearing brief
04 / Applications
Where speed, cleanliness, and active control pay.
Turbomachinery
Compressors, expanders, turbines, and generators with high speed and rotor-dynamic demands.
High-speed pumps
Oil-free support, clean process boundaries, speed, and controlled touchdown behavior.
Compressors + blowers
Reduced contact wear, condition signals, active vibration response, and process integration.
Flywheels
Low steady loss, vacuum operation, rotor containment, long dwell, and fault protection.
High-speed test rigs
Adjustable support dynamics, orbit measurement, controlled excitation, and flexible commissioning.
Specialty process tools
Lubricant-free operation where contamination, vacuum, or controlled vibration dominate.
05 / FAQ
Magnetic-bearing questions.
How does an active magnetic bearing work?
Position sensors measure rotor displacement, a controller calculates corrective forces, and power amplifiers drive electromagnets to keep the rotor centered.
Why are touchdown bearings required?
They protect the machine during startup, shutdown, overload, controller faults, power loss, or disturbances beyond the magnetic bearing's force capacity.
Do magnetic bearings need lubrication?
The magnetic gap does not need contact lubrication during normal operation. Touchdown bearings and other machine components may still require lubrication or dry-running materials.
Can magnetic bearings remove all vibration?
No. They can measure and influence rotor motion within force, bandwidth, stability, sensor, and structural limits. The rotor, process, motor, foundation, and controls still set the total vibration behavior.