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Fault tolerant homopolar magnetic bearings with flux invariant control

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Abstract

The theory for a novel fault-tolerant 4-active-pole homopolar magnetic bearing is developed. If any one coil of the four coils in the bearing actuator fail, the remaining three coil currents change via an optimal distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. The hompolar magnetic bearing thus provides unaltered magnetic forces without any loss of the bearing load capacity even if any one coil suddenly fails. Numerical examples are provided to illustrate the novel fault-tolerant, 4-active pole homopolar magnetic bearings.

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Abbreviations

μ0 :

Permeability of air

a 0 :

Pole face area of an active pole

g 0 :

Nominal air gap in active pole plane

x, y :

Journal displacements

H c :

Coercive force of a permanent magnet

L pm :

Length of a permanent magnet

S:

Flux fringing factor

ϕ j :

Flux through the j-th pole

i j :

Currents through the j-th pole

n:

Number of coil turns

R j :

Air gap reluctance

R R :

Permanent magnet reluctance

V cx ,V cy :

x andy control voltages

Ω:

Rotating speed

θ:

Pole angle

I:

Current vector

T:

Current distribution matrix

K p ,K d :

Proportional and derivative gains

λ:

Lagrange Multiplier

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  1. Division of Mechanical and Automation Engineering, Kyungnam University, Masan, 631-701, Kyungnam, Korea

    Uhn Joo Na

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  1. Uhn Joo Na
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Na, U.J. Fault tolerant homopolar magnetic bearings with flux invariant control. J Mech Sci Technol 20, 643–651 (2006). https://doi.org/10.1007/BF02915981

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  • DOI: https://doi.org/10.1007/BF02915981

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