Passive Magnetic Bearings Research Articles

Further studies of magnetic levitation using high temperature superconductors

The phenomenon of Meissner effect levitation of permanent magnets bp high temperature superconductor (HTS) materials continues to evoke interest because of its potential applicability in ultra-lop friction passive magnetic bearings and becuase it provides a novel probe of vortex dpnamics. Nep experimental results are presented phich extend previous measurements of friction in high speed high temperature superconductor bearings. Studies of magnetic levitation in permanent magnet/HTS thin-film systems are discussed. An updated assessment of the practicalitp of HTS-based magnetic bearings is presented.

Standardized measurements of interaction forces in autostable superconducting magnetic bearings

Abstract Passive magnetic bearings involving superconductors combined with permanent magnets have great potential for future utilization in systems that are exceptionally critical concerning friction and wear. In the field of power systems, possible applications of these superconducting magnetic bearings include flywheels and cold machines such as generators, motors and cold compressors. Present bearing designs are based on the high-temperature superconductor YBa2Cu3O7. In order to investigate the capabilities of these materials and to establish an optimized bearing design, we have built a system that allows precise and reproducible measurements of interaction forces between permanent magnets and superconductors. Different sizes and geometries and various configurations can be accommodated. Our intention is to contribute to a standardization of the experimental technique.

A formula for the levitation force between magnetic disks

Permanent magnet disks are commonly used as passive magnetic bearings for magnetic suspension applications. A closed-form expression is presented for computing the levitation force between magnetic disks. This expression enables rapid parametric studies of the levitation force relative to material properties, dimensions, and spacing. It is easily implemented in any programming environment, and requires only a few minutes of run time on a personal computer. It is tested using finite element analysis. >

Stacked structures of passive magnetic bearings

The stiffness of magnetic bearings composed of only two permanent magnet rings is limited. To increase this stiffness, stacked structures are used. Conventional stacking is obtained by placement of the magnetizations in opposition. This article presents another type of stacking with rotating magnetization direction (RMD), which improves the stiffness by about a factor of 2 in comparison with the conventional stack.

Reliability of turbomolecular vacuum pumps: A comparison of rolling element and magnetic bearing systems

Turbomolecular pumps (TMP) are introduced as high‐vacuum pumps in a wide range of vacuum applications. High reliability, but also contamination‐free operation, low vibrations, and free choice of mounting position are customers demands that directly depend on the choice of the bearing system. Most of the infield TMPs use rolling element bearings that are lubricated by oil or grease. An increasing number of TMPs show active magnetic bearings. A new generation of TMPs use a passive magnetic bearing design. This paper compares the design and performance characteristics of the most common rolling element bearing systems to the more advanced magnetic bearing systems, considering in reliability, hydrocarbon contamination, vibration intensity, choice of mounting position, and costs. The comparison is based on design considerations and on relevant test results, i.e., lifetime tests and lubrication film measurements on TMPs with rolling element bearings. Based on this systematic and empirically founded comparison, this paper gives a guideline for chosing the appropriate TMP and bearing system for a certain range of applications. Furthermore, the paper tries to give a perspective by showing future lines of development of bearing systems for TMPs.

Impact of magnetic bearing rotor design on satellite nutational stability

A linearized mathematical model of a three-axes stabilized symmetric satellite equipped with a magnetic bearing momentum wheel is presented. By an approximative analysis a closed form solution of the eigenvalue problem is derived which permits a quantitative assessment of bearing compliance impact on the satellite nutation. This nutational motion may become unstable due to rotor energy losses. Two various design concepts of magnetic suspension systems, i.e., passive and active magnetic bearings, are investigated for analyzing this effect. The theoretical results are verified by air bearing tests, indicating that actively controlled magnetic bearings can actually be designed to avoid the nutational instability.

On the Dynamic Stability of a Passive Magnetic Radial Bearing with an Eight-Pole Stator

自己制御形8極ラジアル磁気軸受は静的安定性を持っているが,動的安定性に欠けている。この磁気軸受の静特性について理論解析したものも若干みられるが,動的安定性について理論解析されたものはみられない。そこで本研究は非線形方程式を平衡点付近で線形化し,系の特性方程式をもとめて,静的にも動的にも安定する領域を明らかにした。また,この解析結果は実験結果と比較検討され,解析は妥当であることがわかった。

Passive magnetic bearings with soft magnetic materials

The magnetic forces exerted between soft magnetic material components are used in passive magnetic bearings. Several methods of calculation for these systems are presented. We have computed the forces by the numerical method of finite elements. The results have been used to optimize the bearing dimensions.

Low-Cost Magnetic Bearing Reaction Wheel

This paper deals with the design and realization of a magnetic bearing reaction wheel and with measurements obtained from a test model. The development efforts were aimed at realizing a mainly passive magnetic bearing reaction wheel at low cost and high reliability. A two-axis active magnetic bearing is described in detail with special emphasis on the rotor dynamics and the control system design. Design details of the bearing, the rotor and the ironless DC drive motor are shown. Special emphasis is placed on an emergency bearing which maintains reduced bearing functions in case of a failure and simultaneously acts as a mechanical stop during launch phase. In addition, the electronics provided for the bearing and the commutation is described. Performance data and test results obtained with a test model are presented in the form of figures and tables.

Passive magnetic bearings with permanent magnets

The various geometrical dispositions which allow to realize passive magnetic bearings with permanent magnets, have been Known for several decades. Devices running by attraction were the first to be built. When new magnets, which can be used in repulsion appeared on the market (SmCo 5 ), new types of passive magnetic bearings, running by repulsion, started to be made. Up to now, to our knowledge, most of the devices realized have been made with radially magnetized rings. We proved that for identically shaped bearings, strengths and stiffnesses were exactly the same in both magnetic configurations : radial and axial magnetization. The proof is only based on the rigidity of the magnetization. These results are still true for axial or radial passive bearings, and can also be used for devices in attraction. Ring shaped magnets with radial magnetization are usually made of several sectors stuck together. Axial magnetization is much easier to manufacture because large sized rings are already industrially provided.