DE102008034553A1 - Unipolar radial magnetic bearing for bearing shaft, has magnetic coils attached at two poles and controllable so that vectorial sum of magnetic fluxes through three poles are zero, where poles are angular symmetrically arranged around axis - Google Patents

Abstract

The bearing (15) has a stator (10) with three poles (9a-9c), where magnetic coils (11a, 11c) are attached at the two poles. The magnetic coils are controllable such that a vectorial sum of magnetic fluxes (psi a-psi c) through the poles is zero. Each magnetic coil includes a winding wound around each pole. The poles are angular symmetrically arranged around a rotational axis (L) of the bearing. A sensor device e.g. Hall sensor, determines a relative position of a rotor to the stator, and includes a control switch for adjusting electrical currents in the coils.

Description

The The invention relates to a unipolar radial magnetic bearing with a Stator with m ≥ 3 Poland and n solenoids.

active Magnetic bearings of rotating shafts are common constructed according to the reluctance principle. Through the magnetic field can only attractive forces be generated between the magnetic pole in the stator and the shaft. That's why to stabilize the position in two spatial axes at least 3 independent Magnetic poles required (eg offset by 120 °). Usual bearings even have four offset by 90 ° Pole on to independent Position controls for to be able to realize the x- and the y-axis. Each magnetic pole is included the typical arrangements also a separate winding, d. h. that that as the minimum for a bearing in two axes three electrically independent windings be viewed, so m = n is present.

The individual magnetic poles can in the case of heteropolar or homopolar orders (as the case may be, whether the flow goes through the shaft in axial or radial direction) magnetically independent of each other be built or they can additionally magnetically coupled in the case of unipolar arrangements be. The latter have advantages through simpler construction and sheet metal of the rotor, but are technically complicated by the magnetic coupling.

It It is the object of the present invention to provide a simpler unipolar to provide radial magnetic bearing.

These Task is by means of a unipolar radial magnetic bearing after the independent one Claim solved. Preferred embodiments are in particular the dependent ones claims removable.

The unipolar radial magnetic bearing has a stator with at least three (m ≥ 3) Poland and n magnetic coils on. Each of the n solenoids is on one associated Pole attached. Instead of the unipolar radial magnetic bearing as before Equipped with one coil per pole (m = n), now fewer coils used as a pole, according to the condition n <m. The n magnetic coils are controlled so that a vectorial sum of the magnetic rivers is substantially zero by all poles.

to easier control, each of the magnetic coils preferably a single winding wound around the respective pole.

to easier control, the poles are symmetric about one Rotary axis of the magnetic bearing arranged.

It Furthermore, a magnetic bearing is preferred in which n = m - 1, d. h., That the stator has one more pole than solenoids.

It a magnetic bearing is preferred which is equipped with exactly m = 3 poles.

To the Compensation of disturbances and stray fields, a magnetic bearing is preferred, further that a Sensor device, eg. B. with a Hall sensor, to determine a relative position of a rotor to the stator, as well as a Control circuit for adjusting the electrical currents in the Windings (manipulated variable) on the basis of a position determined by means of the sensor device of the rotor (controlled variable) to the position of the rotor at a desired position relative to the stator to keep.

In The following figures illustrate the invention with reference to an embodiment described in more detail schematically. It can for better clarity identical or equivalent elements with the same reference numerals be provided.

1 shows in an oblique view a cut magnetic bearing with a pot magnet;

2 schematically shows the radial bearing 1 in plan view along the axis of rotation or longitudinal axis;

3 in a representation analogous to the representation 2 an inventive radial bearing;

4 a magnetic equivalent circuit diagram of the radial bearing 3 ,

1 shows a magnetic Radiax bearing 1 with a shaft to be stored 2 , The wave 2 is axially by means of a magnetic thrust bearing 3 mounted on the spaced on both sides in each case a known magnetic radial bearing 4 followed.

The thrust bearing 3 has two adjacent cylindrical electromagnets (pot magnets) 5 on which the shaft 2 surrounded without contact and in their serving as a magnetic core housings 6 one each the shaft 2 annular surrounding winding 7 is included. To ensure the axial bearing is one in a space between the pot magnet 5 on the shaft 2 vertically mounted bearing disc 8th used of magnetic material. The housing 6 of the pot magnet 5 that's the winding 7 includes in the Single side floor plates 13 on and radial walls 14 on. The wave 2 loosely protrudes through a recess (without reference numeral) of the housing 6 ,

The bearing disc 8th is from the pot magnets 5 separated by an air gap (without reference numeral). The bearing disc 8th thus turns with the shaft 2 against the pot magnets 5 with and thus provides the rotor of the thrust bearing 3 dar. The bearing disc 8th is usually considered a part of the thrust bearing 3 considered. The bearing disc 8th would have according to previous knowledge nis radially laminated (in the form of cake pieces), which is not useful manufacturing technology. Nor is a ferrite material or pressed iron powder in question. For some magnet arrangements, a similar problem also occurs in radial bearing. Is the rotor 8th not laminated, according to previous knowledge, a signal evaluation of the position-dependent inductance, however, can only be done with relatively low measurement frequencies or the signal swing of the inductance to rotor position is relatively low. Consequently, a considerable effort must be invested in a signal evaluation. The high frequency portion of the magnetic flux utilized to position the rotor has only a relatively small amplitude relative to the substantially DC portion of the field for force generation. Therefore, even a small improvement in the penetration depth would bring a significant improvement in signal acquisition.

The radial bearing 4 Here, more conventionally, there are three strut-shaped poles acting as respective magnetic cores 9 a static frame or stator 10 wound windings (solenoids) 11 which is angularly symmetrical about the shaft 2 are arranged. The stator 10 surrounds one on the shaft 2 attached magnetic element 12 with an annular outer contour ('rotor'). The rotor 12 is from the stator 10 through an air gap 14 separated.

2 shows simplifying the radial bearing 4 out 1 in a plan view along the axis of rotation or longitudinal axis L. The stator 10 has an annular frame 13 with angular symmetry about the axis of symmetry (longitudinal axis or axis of rotation of the shaft) L arranged, inwardly directed striven-shaped poles 9a . 9b . 9c auf, on each of which here only schematically indicated winding (coil) 11a . 11b . 11c is wound up. With current flowing through the windings 11a . 11b . 11c will be in the poles 9a . 9b . 9c generates a magnetic flux φa, φb, φc, thereby attracting forces Fa, Fb, Fc between the poles 9a to 9c and the rotor 12 are generated, which the rotor 12 through a respective air gap 14a . 14b . 14c from the stator 10 keep separate. Such a radial bearing 4 in unipolar construction has, as mentioned above, the property that the (here) three poles 9a . 9b . 9c are magnetically coupled, that is, that there is no simple direct relationship between the currents in a winding 11a . 11b . 11c and the magnetic fluxes φa, φb and φc, respectively, and consequently the forces Fa, Fb and Fc at this pole 9a . 9b respectively. 9c gives. It therefore always has the entire warehouse 4 are considered, since the rivers φa, φb, φc on the other poles 9a . 9b . 9c Close and there contribute to the forces Fa, Fb, Fc.

3 shows a magnetic radial bearing according to the invention 15 , In this radial bearing 15 The magnetic coupling is exploited, a three-pole unipolar bearing with only two windings 11a . 11c build. On the example selected winding 11b out 2 is thus omitted.

4 shows for describing the relationships of the device 3 an equivalent equivalent magnetic circuit diagram. The magnetic voltage sources Ua and Uc correspond to the excitation currents Ia and Ic in the two windings 11a respectively. 11c in 3 and may also be referred to as magnetic flux with the symbol Θ. The magnetic voltage U can be calculated to a good approximation from the winding number and the electrical current conducted through the winding. The magnetic resistances RMa, RMb, RMc are dependent on the air gap 14a . 14b respectively. 14c at the respective pole 9a . 9b respectively. 9c and the passage area for the magnetic flux. The "magnetic currents" of the equivalent circuit correspond to the fluxes φa, φb, φc and describe the forces Fa, Fb and Fc at the respective pole 9a . 9b respectively. 9c , The magnetic flux φ is calculated according to the reluctance principle from U / RM.

From the equivalent circuit it was found that with only two magnetic voltage sources Ua and Uc any "mag netic current" (magnetic flux) in all three poles and thus arbitrary forces Fa, Fb, Fc at all three poles 9a . 9b . 9c can be generated on the assumption that the vectorial sum of all rivers in the camp 15 is equal to 0, ie the condition φa + φb + φc = 0 is fulfilled by the desired flows (if no significant leakage flux occurs). This means that the three magnetic forces Fa, Fb, Fc can be set as desired via only two control currents Ia, Ic.

Of the size Advantage of such an arrangement is the saving of a complete Winding including cabling, power electronics and current regulator.

It Thus, the magnetic coupling of the three poles of a radial Unipolar magnetic bearing exploited, so that in this embodiment only two windings the rivers in three poles and thus set three magnetic forces independently can be.

Of course it is the present invention is not limited to the embodiment shown limited.

So can at a radial bearing with four poles the rivers in the poles and thus the magnetic forces independent with only three windings can be adjusted from each other, etc.

Possible low leakage flux or disturbance variables (influence of the iron circle, etc.), so that the magnetic forces Fa, Fb and Fc are not quite can correspond to the theoretical value, by means of a regulation the position of the rotor relative to the stator are taken into account (position control). Thus, the radial bearing a sensor device for determining a Relative position of the rotor to the stator, as well as a Control circuit for adjusting the electrical currents in the Windings (manipulated variable) on the basis of a position determined by means of the sensor device of the rotor (controlled variable) to to keep the position of the rotor at a desired position.

Claims (6)

Unipolar radial magnetic bearing ( 15 ) with a stator ( 10 ) with in ≥ 3 poles ( 9 ; 9a . 9b . 9c ) and n magnetic coils ( 11a . 11c ), where n poles ( 9a . 9c ) in each case a magnetic coil ( 11a . 11c ), where n <m and the magnetic coils ( 11a . 11c ) are controllable so that a vectorial sum of the magnetic fluxes (φa, φb, φc) at least through all the poles ( 9 ; 9a . 9b . 9c ) is substantially zero. Magnetic bearing ( 15 ) according to claim 1, in which each of the magnetic coils ( 11a . 11c ) a single around the respective pole ( 9a . 9c ) wound winding. Magnetic bearing ( 15 ) according to claim 1 or 2, wherein the poles ( 9a . 9b . 9c ) angularly symmetrical about an axis of rotation (L) of the magnetic bearing ( 15 ) are arranged. Magnetic bearing ( 15 ) according to one of the preceding claims with n = m - 1 magnetic coils ( 11a . 11c ). Magnetic bearing ( 15 ) according to one of the preceding claims with m = 3 poles ( 9 ; 9a . 9b . 9c ). Magnetic bearing ( 15 ) according to one of the preceding claims, further comprising a sensor device for determining a relative position of a rotor ( 12 ) to the stator ( 10 ) and comprising a control circuit for adjusting the electric currents (Ia, Ic) in the coils ( 9a . 9c ) on the basis of a determined by means of the sensor device position of the rotor ( 12 ) to the position of the rotor ( 12 ) to keep at a desired position.