Magnetic bearing motor for chopper applications

Most magnetic bearing concepts are based on reluctance forces. A magnetic flux in the air gap between stator and rotor generates these forces whereas the flux is regulated by stator currents. In this magnetic bearing type, the rotational speed is limited due to increasing eddy current losses in the rotor and stator iron, a limited actuator bandwidth and a high reactive power demand. Therefore, magnetic bearings have only been successful up to rotational speeds of about 120,000 rpm. To overcome these rotational speed limits, Celeroton has researched a new magnetic bearing concept. The new bearing enables rotational speeds of 500,000 rpm and more, which represents the world record for a magnetically levitated drive system.

The bearing is based on Lorentz forces instead of reluctance forces. A winding, which lies in the air gap between the rotor magnets and the stator iron, generates these forces – electric current in the winding regulates them. The magnetic field of the permanent magnet can also be used for the generation of the torque, which enables a short design of the motor as so called bearingless motor.

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• Optical systems with high rotational speeds such as beam choppers and rotating mirrors
  These applications are operated in vacuum or helium atmosphere to minimize air friction losses, and to protect the optic from pollution. The disadvantages of magnetic bearings regarding space requirements and complexity are not critical, as the whole system is much bigger and more complex than the bearing itself.

• Reaction wheels for satellites
  Reaction wheels are used in satellites to control and stabilize the attitude in the space. They are moved to the desired position by rotational speed regulation. As satellites depend on light components, reaction wheels are often designed with the aim to reduce weight by increasing the rotational speed. Furthermore, they should generate the lowest possible vibrations suitable for the operation in full or partial vacuum. Therefore, the magnetic bearing turns out to be the optimal solution for this application.

• Special centrifuges
  Special centrifuges and further physical test environments, such as the mechanical acceleration of particles.

If you are designing a new system for ultra-high speeds and are thinking about magnetic bearings, please contact us​​​​​​​ to discuss your requirements.