GB1500809A - Radial active magnetic bearing having a rotating drive - Google Patents

Abstract

1500809 Automatic control of position LICENTIA PATENT VERWALTUNGS GmbH 10 Feb 1975 [9 Feb 1974 30 Nov 1974] 5602/75 Heading G3R The rotating field of a (three phase) dynamo electric machine has superimposed upon it a field which functions as a radial active bearing and is adjusted in response to a measurement of the air gap, the two fields having pole pairs differing in number by one. In the embodiments the drive field 1 has two poles per phase and the bearing control field 26 four, but these may be interchanged for starting. As shown, the gap is measured by three differential pairs of sensors, each functioning as a transformer with a movable core (radial movement of the rotor). They have primary windings 2, 3 (for the R phase) energized from drive current transformers ST or the drive current directly and secondaries 4, 5, star connected, with auxiliary secondaries K connected all in series between the star point of the main secondaries and that of a series tuned damping network 30 ... 32, through which the sensors control the bearing field 26. The windings K are to damp unwanted modulation of the restoring force which can give rise to rotor oscillations. The damping circuits are connected through phase adjusting bridge networks 20-22 and amplifiers 23 ... 25 supplying the bearing field 26. In an alternative embodiment, Figs. 3 and 4 (not shown), the two fields are provided by a single set of bifurcated windings, energized from a twelve phase transformer in two and four pole configuration for the drive and bearing fields respectively. Instead of the separate gap sensors shown the (separate) control windings themselves may be used. Figs. 5-7 (not shown), illustrate three such arrangements using feedback amplifiers as "negative resistance elements". The feedback may be non- linear. For elongated rotor machines two bearing arrangements according to the invention are used, but it is explained that for short rotors one bearing only is required, and the rotor pole face can be convex and the stator face convex or saddleshaped. Where the rotor is external and the stator internal, the rotor and stator pole faces may be spherical.