<p>A novel homopolar electrodynamic bearing, together with a suitable permanent magnet drive, have been developed for high-speed applications where low losses and high reliability are essential and exclude the use of ball bearings, and yet where active magnetic bearings offer a too complex system solution. Considered applications are small turbomolecular vacuum pumps, and maintenance free flywheels for energy storage in remote telecom and satellite systems. Other upcoming areas where these bearings offer interesting technical and economic solutions are compressors for fuel cells and heat pumps, applications which normally suffer from short bearing lifetime.</p><p>Unlike active magnetic bearings, forces are produced in electrodynamic bearings without any control electronics, thanks to stabilizing eddy currents induced by permanent magnets. In the novel homopolar concept eddy current losses are reduced to a minimum using a homopolar design with ring magnets instead of multipole or Halbach arrays.</p><p>Currents and forces are simulated using steady state 3D-FEM analysis, which can take velocity into account using an implemented Minkowski transform. From these results an analytical model has been developed, and the results are compared. The results are converted into useful rotordynamic data that is easily understood by machine engineers.</p><p>The bearing has been experimentally tested in a rebuilt turbomolecular vacuum pump up to 90,000 rpm. Bearing forces have been accurately measured on a specially designed spring suspended scales, in which the bearing rotor is powered with the permanent magnet drive. Comparison of measured data with results from the 3D-FEM analysis shows excellent agreement.</p>

Mancais magnéticos com controle uniaxial são mancais híbridos que combinam um mancal radial por imãs permanentes e um mancal axial eletromagnético com controle ativo. Estes mancais, a despeito das vantagens com relação a outras modalidades de mancais magnéticos, têm como principal deficiência a ausência de capacidade de amortecimento de vibrações radiais do rotor. De modo a eliminar tal deficiência, esta tese propõe um novo mancal magnético híbrido que conjuga um mancal com controle uniaxial a um mancal eletrodinâmico. Esta tese tem como objetivo investigar e demonstrar a eficácia desta solução. O objetivo final é apresentar um mancal magnético de elevado desempenho, de arquitetura simples e robusta, com possibilidades de aplicação em máquinas rotativas de alta velocidade. O mancal aqui proposto tem como base um mancal de controle uniaxial cuja arquitetura é definida de modo a apresentar elevada rigidez radial, elevada folga mecânica na porção rotativa, reduzida inércia no rotor, assim como simplicidade na construção e funcionamento. Para tanto, aqui se emprega mancais radiais com imãs disposto em camadas, operando em repulsão. Na direção axial, são usados atuadores eletromagnéticos compatíveis com a elevada rigidez gerada pelos mancais radiais. A estes mancais são associados mancais eletrodinâmicos homopolares de dois tipos, de fluxo magnético axial e de fluxo radial. Definido conceitualmente o novo mancal, protótipos foram desenvolvidos e foram realizados ensaios de validação do conceito do novo mancal, assim como de verificação do desempenho do protótipo. Com relação ao mancal proposto, foi verificada uma levitação estável do rotor e, obtida uma rigidez radial de 44 N/mm mediante uma folga de 2,5 mm. São valores que superam quaisquer resultados encontrados em literatura sobre mancais similares. Em seguida, demonstrou-se, ao menos até uma rotação de 35 Hz (2.100 rpm), a eficácia do mancal eletrodinâmicos de fluxo axial no amortecimento de movimentos assíncronos do rotor. / Single axis controlled magnetic bearings are hybrid bearings that combine a radial bearing based on permanent magnets and an electromagnetic bearing with active control. Such bearings, despite advantages with respect to other modalities of magnetic bearings, present an important problem of absence of vibration damping capability in the radial directions of the rotor. In order to solve this problem, this thesis proposes a new hybrid magnetic bearing that conjugates a single axis controlled bearing with an electrodynamic bearing. This thesis aims investigate and demonstrate the efficiency of the proposed solution. The final goal is to present a magnetic bearing with high capabilities, of simple architecture and robust, with possibilities for applications in high speed rotary machines. The presented bearing has, as the base, a single axis controlled bearing with an architecture suitable for achieving high radial stiffness, large gap in the rotary portion, low rotor inertia, as well as simplicity in its construction and operation. For this, the bearing employs radial bearings based on magnets arranged in layers operating in repulsion mode. In the axial direction, it uses electromagnetic actuators compatible with the high radial stiffness generated by radial bearings. These bearings are associated with electrodynamic homopolar bearings of two types: one of axial magnetic flux and other with radial flux. Once, the new bearing is defined conceptually, tests are conducted to validate the principle of the new bearing, as well, tests to evaluation of the efficiency of the prototype. With respect to the proposed bearing, a stable levitation of the rotor is obtained. Also, a radial stiffness of 44 N/mm is achieved with a gap of 2.5 mm. These values are higher than any results presented in literatures related to similar bearings. Finally, it is demonstrated that at rotations speeds of until 35 Hz (2,100 rpm), the electrodynamic of axial flux is efficient to attenuate asynchronous motions of the rotor.

A novel homopolar electrodynamic bearing, together with a suitable permanent magnet drive, have been developed for high-speed applications where low losses and high reliability are essential and exclude the use of ball bearings, and yet where active magnetic bearings offer a too complex system solution. Considered applications are small turbomolecular vacuum pumps, and maintenance free flywheels for energy storage in remote telecom and satellite systems. Other upcoming areas where these bearings offer interesting technical and economic solutions are compressors for fuel cells and heat pumps, applications which normally suffer from short bearing lifetime. Unlike active magnetic bearings, forces are produced in electrodynamic bearings without any control electronics, thanks to stabilizing eddy currents induced by permanent magnets. In the novel homopolar concept eddy current losses are reduced to a minimum using a homopolar design with ring magnets instead of multipole or Halbach arrays. Currents and forces are simulated using steady state 3D-FEM analysis, which can take velocity into account using an implemented Minkowski transform. From these results an analytical model has been developed, and the results are compared. The results are converted into useful rotordynamic data that is easily understood by machine engineers. The bearing has been experimentally tested in a rebuilt turbomolecular vacuum pump up to 90,000 rpm. Bearing forces have been accurately measured on a specially designed spring suspended scales, in which the bearing rotor is powered with the permanent magnet drive. Comparison of measured data with results from the 3D-FEM analysis shows excellent agreement. / QC 20101026

Mancais magnéticos com controle uniaxial são mancais híbridos que combinam um mancal radial por imãs permanentes e um mancal axial eletromagnético com controle ativo. Estes mancais, a despeito das vantagens com relação a outras modalidades de mancais magnéticos, têm como principal deficiência a ausência de capacidade de amortecimento de vibrações radiais do rotor. De modo a eliminar tal deficiência, esta tese propõe um novo mancal magnético híbrido que conjuga um mancal com controle uniaxial a um mancal eletrodinâmico. Esta tese tem como objetivo investigar e demonstrar a eficácia desta solução. O objetivo final é apresentar um mancal magnético de elevado desempenho, de arquitetura simples e robusta, com possibilidades de aplicação em máquinas rotativas de alta velocidade. O mancal aqui proposto tem como base um mancal de controle uniaxial cuja arquitetura é definida de modo a apresentar elevada rigidez radial, elevada folga mecânica na porção rotativa, reduzida inércia no rotor, assim como simplicidade na construção e funcionamento. Para tanto, aqui se emprega mancais radiais com imãs disposto em camadas, operando em repulsão. Na direção axial, são usados atuadores eletromagnéticos compatíveis com a elevada rigidez gerada pelos mancais radiais. A estes mancais são associados mancais eletrodinâmicos homopolares de dois tipos, de fluxo magnético axial e de fluxo radial. Definido conceitualmente o novo mancal, protótipos foram desenvolvidos e foram realizados ensaios de validação do conceito do novo mancal, assim como de verificação do desempenho do protótipo. Com relação ao mancal proposto, foi verificada uma levitação estável do rotor e, obtida uma rigidez radial de 44 N/mm mediante uma folga de 2,5 mm. São valores que superam quaisquer resultados encontrados em literatura sobre mancais similares. Em seguida, demonstrou-se, ao menos até uma rotação de 35 Hz (2.100 rpm), a eficácia do mancal eletrodinâmicos de fluxo axial no amortecimento de movimentos assíncronos do rotor. / Single axis controlled magnetic bearings are hybrid bearings that combine a radial bearing based on permanent magnets and an electromagnetic bearing with active control. Such bearings, despite advantages with respect to other modalities of magnetic bearings, present an important problem of absence of vibration damping capability in the radial directions of the rotor. In order to solve this problem, this thesis proposes a new hybrid magnetic bearing that conjugates a single axis controlled bearing with an electrodynamic bearing. This thesis aims investigate and demonstrate the efficiency of the proposed solution. The final goal is to present a magnetic bearing with high capabilities, of simple architecture and robust, with possibilities for applications in high speed rotary machines. The presented bearing has, as the base, a single axis controlled bearing with an architecture suitable for achieving high radial stiffness, large gap in the rotary portion, low rotor inertia, as well as simplicity in its construction and operation. For this, the bearing employs radial bearings based on magnets arranged in layers operating in repulsion mode. In the axial direction, it uses electromagnetic actuators compatible with the high radial stiffness generated by radial bearings. These bearings are associated with electrodynamic homopolar bearings of two types: one of axial magnetic flux and other with radial flux. Once, the new bearing is defined conceptually, tests are conducted to validate the principle of the new bearing, as well, tests to evaluation of the efficiency of the prototype. With respect to the proposed bearing, a stable levitation of the rotor is obtained. Also, a radial stiffness of 44 N/mm is achieved with a gap of 2.5 mm. These values are higher than any results presented in literatures related to similar bearings. Finally, it is demonstrated that at rotations speeds of until 35 Hz (2,100 rpm), the electrodynamic of axial flux is efficient to attenuate asynchronous motions of the rotor.

High speed applications demands with a need for lower energy consumption lead to designing new types of bearings. In the last decades magnetic bearing, which would be able to obtain passive stable levitation using regular materials at room temperature, has been searched. This has lead to development of electrodynamic bearing based on eddy currents principle. Currently the electrodynamic bearings are still not fully explored and further research is needed. The aim of the work is to describe the theory about modern magnetic bearing, analysis and design of electrodynamic bearing according to given parameters. The finite element method is used for further analysis and evaluate behaviour of its properties.