Experimental and numerical evaluation of rotation speed degradation of radial type superconducting magnetic bearing

Demachi, Kazuyuki; Miura, Akira; Uchimoto, Tetsuya; Miya, Kenzo; Higasa, Hiromasa; Takahata, Ryoichi; Kameno, Hiroo

doi:10.1016/s0921-4534(01)00438-5

Cited by 11 publications

(3 citation statements)

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“…These applications are generally based on the interactions between the permanent magnets (PMs) and superconductors. Among the most important are the superconducting magnetic levitation systems which can be utilized as stabilizers in superconducting energy storage devices [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Translational and rotational dynamic analysis of a superconducting levitation system

Cansız¹,

Hull²,

Gündoğdu³

2005

Supercond. Sci. Technol.

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The rotational dynamics of a disc-shaped permanent magnet rotor levitated over a high temperature superconductor was studied experimentally and theoretically. The interaction between the rotor magnet and the superconductor was modelled by assuming the magnet to be a magnetic dipole and the superconductor a diamagnet. In the magnetomechanical analysis of the superconductor part, the frozen image concept was combined with the diamagnetic image, and the damping in the system was neglected. The interaction potential of the system is the combination of magnetic and gravitational potentials. From the dynamical analysis the equations of motion of the permanent magnet were stated as a function of lateral, vertical, tilt, precision and rotating angles. The vibration behaviour and correlation of the vibration of one direction with that of another were determined with a numerical calculation based on the Runge-Kutta method. The various vibrational frequencies identified were vertical, radial, tilt, precession and rotation. The tests performed for experimental verifications were translational and rotational. The permanent magnet was 'spun up' under vacuum conditions to analyse the dynamics of the free 'spin down' behaviour of the permanent magnet.

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Section: Introductionmentioning

confidence: 99%

Translational and rotational dynamic analysis of a superconducting levitation system

Cansız¹,

Hull²,

Gündoğdu³

2005

Supercond. Sci. Technol.

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“…But the characteristics of measurement results were against the prediction derived from cause-A and B. Namely, the degradation was remarkably enhanced when the levitation force of the SMB increased [2]. Such an enhancement cannot occur due to cause-A and B, because the degradation by the inhomogeneous magnetic field of the PM rotor should be independent of the levitation force [3], [4].…”

Section: Mechanism Of Rotation Speed Degradation In Smbmentioning

confidence: 86%

Numerical and experimental analysis of the rotation speed degradation of superconducting magnetic bearings

Shiraishi

Demachi

Uesaka

et al. 2003

IEEE Trans. Appl. Supercond.

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The suppression of the rotation speed degradation of the Superconducting Magnetic Bearing (SMB) with the Permanent Magnet (PM) rotor including the layered insulator thin films is studied.The SMB system consists of the superconductor stator and the PM rotor, and is a no-contact bearing system using the levitation force between them. The SMB was expected to be applied to the electric power storage flywheel system because friction causes the rotation speed degradation and decreases the energy storage capability. However, it was found that the electromagnetic friction of the SMB was not zero, due to electromagnetic forces; 1) the magnetic force interaction between the inhomogeneous magnetic field of the PM rotor and the eddy current it induces in the cryostat, 2) the magnetic force between the inhomogeneous magnetic field of the PM rotor and the shielding current it induces in the superconductor, 3) the magnetic force between the magnetic field of superconductors yielding the levitation force and the eddy current induced in the PM rotor. This magnetic field of superconductor is inhomogeneous too, because the superconductors consist of several HTSC bulks. In this research, it was found that the 3rd phenomenon is most significant. So, we use the advanced PM rotor including the layered insulator thin films to suppress its eddy current and the degradation of the rotation speed. Using our SMB equipment, the rotation speed degradation was measured using the PM rotors with/without the insulator thin films and the electromagnetic frictions were compared to each other.Index Terms-Eddy current, insulating film, rotation speed degradation, superconducting magnetic bearing (SMB).

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“…A group of scientists [92] proposed a formula to model the magnetic field inhomogeneity of a PM and then performed simulations to model the relation between inhomogeneity and rotational loss. According to their simulations, rotational loss is proportional to the second power of the ratio of magnetic field inhomogeneity to the mean value of magnetic field.…”

Section: Literature Review 16mentioning

confidence: 99%

AC Losses in Superconducting Magnetic Bearings

Siamaki¹

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Since the discovery of high-temperature superconductors, superconducting magnetic bearings have become an icon of applied superconductivity. Their ability to provide passive stable levitation/suspension has attracted much attention for industrial applications such as maglev trains, flywheel energy storage systems, and high speed electrical machines. Paihau-Robinson Research Institute has been working on the design and construction of a 22 kW, 30000 rpm homopolar superconducting motor for a hybrid aircraft propulsion system. Superconducting magnetic bearings seem to be a potential solution to overcome the speed limits imposed by friction and heat in mechanical bearings. Considering the lack of commercial availability of superconducting bearings, the Institute has decided to investigate the challenges involved in developing suitable bearings for ongoing and future projects. The focus of this thesis is to explore the development of suitable low-loss bearings from bulk high-temperature superconductors, and to develop suitable test methodologies that allow the properties and behaviour of high-temperature superconducting bearings to be explored. In order to accurately predict the behaviour of superconducting magnetic bearings, a precise knowledge about the non-linear voltage-current (E-J) relationshipis required for input to simulations. Unlike coated conductors, this cannot be achieved by transport measurements in superconducting bulks. In this thesis, a convenient non-destructive method based on levitation force decay in superconducting bearings is introduced and evaluated to map the non-linear electrical properties in superconducting bulks. Furthermore, fibre Bragg grating sensors are employed in an actual superconducting bearing environment to monitor temperature at the bearing surface. Accurate cryogenic temperature monitoring with large electromagnetic fields present is of great importance in practical applications, and is problematic with conventional electronic sensors. A barrier to commercial application is suspected to be the effects of inhomogeneous magnet, or superconducting, properties on the efficiency of bearings. The key drivers of this, AC loss mechanisms in superconducting bearings are investigated and a new analytical expression is proposed for hysteresis loss in superconducting bearings which takes magnetic field inhomogeneity, magnetic field periodicity, and loss surface distribution into account. This new expression is tested by performing spin-down experiments, and the results are found to be in good agreement. Lastly, a high-speed superconducting motor/generator demonstration is built, which sets a record for the fastest superconducting bearing made in New Zealand. This will enable applications such as flywheel energy storage systems, direct-drive generators and high speed microfans to be explored whilst also providing the opportunity to demonstrate key technology elements such as flux-pumped hightemperature superconducting field windings and low-loss high-speed bearings. AC loss mechanisms at kHz-rated rotational frequencies are also studied with this prototype. The results show that at high rotational frequencies the superconducting bulks are pushed into a resistive flux-flow regime, where AC losses are createdby an eddy-current-like mechanism. This thesis explores two phenomena of practical importance in superconducting bearings, and proves the principle of the application of superconducting bearings for ongoing and future projects in New Zealand.

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Experimental and numerical evaluation of rotation speed degradation of radial type superconducting magnetic bearing

Cited by 11 publications

References 0 publications

Translational and rotational dynamic analysis of a superconducting levitation system

Translational and rotational dynamic analysis of a superconducting levitation system

Numerical and experimental analysis of the rotation speed degradation of superconducting magnetic bearings

AC Losses in Superconducting Magnetic Bearings

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