Bearing control device, magnetic bearing device, rotating machine, and method for setting magnetic bearing device

Abstract

A bearing control device is a bearing control device for a magnetic bearing that is provided with an electromagnet including a coil disposed facing a rotating shaft extending in an axial direction, and that supports the rotating shaft in a non-contact manner so as to be rotatable in a circumferential direction around the axial direction by a magnetic field generated by a current flowing through the coil. The bearing control device includes: a current value acquisition unit that acquires a coil current value, which is a value of a current flowing through a coil; a filter that generates a corrected current value that corrects the coil current value acquired by the current value acquisition unit in accordance with the influence of an eddy current generated by the magnetic flux generated by the coil; and a power amplifier for supplying a current to the coil using a current command value based on the corrected current value as an input.

Description

TECHNICAL FIELD

[0001] The present application relates to a bearing control device, a magnetic bearing device, a rotating machine, and a setting method for a magnetic bearing device.

[0002] This application claims priority from Japanese Patent Application No. 2023-040736 filed on March 15, 2023, and the contents thereof are incorporated herein. BACKGROUND

[0003] In Patent Literature 1, there is disclosed a magnetic bearing device that estimates a magnetic flux generated between an electromagnet on a support body side and an electromagnet target on a supported body side, based on a detection signal of an output control current of a power amplifier that makes a control current flow through a coil on the support body side and a displacement detection signal of the supported body that is magnetically levitated and supported, and feeds back an estimated value of the magnetic flux to the power amplifier.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2002-39178 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the magnetic bearing device, eddy currents are generated around the magnetic flux generated due to the current flowing through the coil. Due to the eddy currents, the generation of the magnetic flux in the coil is hindered, which can result in a decrease in the magnetomotive force in the coil. As a result, this becomes an obstacle to the improvement of the bearing performance of the magnetic bearing device.

[0009] The present application has been achieved in order to solve the above problems, and aims to provide a bearing control device, a magnetic bearing device, a rotating machine, and a setting method for a magnetic bearing device that can suppress the influence caused by the eddy currents generated in the coil and improve the bearing performance.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] To solve the above problems, the bearing control device according to the present application is a bearing control device of a magnetic bearing that has an electromagnet including a coil disposed in opposition to a rotating shaft extending in an axial direction, and supports the rotating shaft in a non-contact manner so as to be free to rotate in a circumferential direction around the axis by a magnetic field generated due to current flowing through the coil, and includes: a current value acquisition section that acquires a value of the current flowing through the coil, that is, a coil current value; a filter that generates a corrected current value that corrects the coil current value acquired by the current value acquisition section according to an influence of eddy current generated by magnetic flux generated by the coil; and a power amplifier that supplies current to the coil based on a current command value based on the corrected current value

[0012] The magnetic bearing device according to the present application includes: a magnetic bearing that has an electromagnet including a coil disposed in opposition to a rotating shaft extending in an axial direction, and supports the rotating shaft in a non-contact manner so as to be free to rotate in a circumferential direction around the axis by a magnetic field generated due to current flowing through the coil; and the bearing control device described above.

[0013] The rotating machine according to the present application includes: a rotating shaft extending in an axial direction; and the magnetic bearing device described above.

[0014] The setting method of the magnetic bearing device according to the present application is a setting method of the bearing control device described above, and includes the steps of: acquiring an impedance I r / V i of the electromagnet; acquiring a term Z ed generated due to the influence of the eddy current calculated according to the following formula (1) when the resistance of the coil is set to R0 and the inductance of the coil is set to L0 ed ; fitting the term Z ed generated due to the influence of the eddy current according to the frequency at the time of rotation of the rotating shaft according to the following formula (2) when Tz, Tp are set to time constants

[0015] [Formula 1]

[0016]

[0017] Effects of the Invention

[0018] The bearing control device, the magnetic bearing device, the rotating machine, and the setting method of the magnetic bearing device according to the present application can suppress the influence of the eddy current generated in the coil and improve bearing performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1It is a diagram showing a schematic configuration of a magnetic bearing device and a rotating machine according to an embodiment of the present invention.

[0020] Figure 2 1 is a diagram showing the hardware configuration of the magnetron device of the magnetic bearing device.

[0021] Figure 3 1 is a diagram showing the functional structure of the magnetron device.

[0022] Figure 4 It is a diagram showing the functional structure of the thrust bearing control unit of the above-mentioned magnetron device.

[0023] Figure 5 1 is a diagram showing an equivalent circuit of the electromagnet of the magnetic bearing device.

[0024] Figure 6 This is a flowchart showing the steps of the setting method of the above-mentioned bearing control device.

[0025] Figure 7 This is a diagram showing an example of fitting a term caused by the influence of eddy current in the setting method of the magnetic bearing device.

[0026] Figure 8 This is a diagram showing another example of fitting a term caused by the influence of eddy current in the setting method of the magnetic bearing device. DETAILED DESCRIPTION

[0027] Hereinafter, with reference to the accompanying drawings, a mode for implementing a bearing control device, a magnetic bearing device, a rotating machine, and a setting method for a magnetic bearing device according to the present invention will be described. However, the present invention is not limited to this embodiment.

[0028] (Structure of Rotating Machinery)

[0029] In the embodiment of the present invention, the rotary machine 1 is, for example, a turbomachine used in a turbo refrigerator, etc. The rotary machine 1 is not limited to a turbomachine, and may be a steam turbine, a gas turbine, a centrifugal compressor, etc.

[0030] like Figure 1 As shown, the rotary machine 1 includes a rotary shaft 11 , a casing 10 , a first impeller 12 , a second impeller 13 , a motor 14 , and a magnetic bearing device 19 .

[0031] The rotating shaft 11 has a cylindrical shape extending in an axial direction Da along the axis O. A thrust ring 18 is provided on a portion of the rotating shaft 11 in the axial direction Da. The thrust ring 18 extends outward from the outer peripheral surface of the rotating shaft 11 in a radial direction Dr centered on the axis O in a flange-like manner.

[0032] The housing 10 is configured to surround the rotation shaft 11 from the outside in the radial direction Dr. Both end portions of the rotation shaft 11 in the axial direction Da protrude from both sides of the housing 10 in the axial direction Da.

[0033] The first impeller 12 is integrally fixed to the end portion on one side (left side) of the rotation shaft 11 in the axial direction Da. The first impeller 12 is rotated in the circumferential direction Dc around the axis O together with the rotation shaft 11, and pressurizes and transports the refrigerant flowing in from the one side in the axial direction Da toward the radial outside. Figure 2

[0034] The second impeller 13 is integrally fixed to the end portion on the other side (right side) of the rotation shaft 11 in the axial direction Da. The second impeller 13 is rotated in the circumferential direction Dc together with the rotation shaft 11, and pressurizes and transports the refrigerant flowing in from the radial outside toward the other side in the axial direction Da. Figure 2

[0035] Thus, the rotary machine 1 having the first impeller 12 and the second impeller 13 becomes a two-stage compression structure that further compresses the refrigerant compressed by the first impeller 12 by the second impeller 13.

[0036] The motor 14 has a rotor core 15 and a stator 16.

[0037] The rotor core 15 is integrally fixed to the outer peripheral surface of the rotation shaft 11. The rotor core 15 has a laminated steel plate structure that is fitted to the outer peripheral surface of the rotation shaft 11. A plurality of permanent magnets (not shown) are provided in the rotor core 15 at intervals along the circumferential direction Dc.

[0038] The stator 16 has a stator core disposed on the outside of the rotor core 15 in the radial direction Dr, and a plurality of stator coils provided in the stator core at intervals along the circumferential direction Dc. The motor 14 generates a rotating magnetic field that rotates in the circumferential direction Dc around the axis O by supplying a current to the stator coils of the stator 16 from the outside. The rotor core 15 rotates in the circumferential direction Dc together with the rotation shaft 11 by causing each permanent magnet to follow the rotating magnetic field generated by the stator 16.

[0039] The magnetic bearing device 19 has a pair of radial magnetic bearings 20 and a thrust magnetic bearing (magnetic bearing) 30.

[0040] The pair of radial magnetic bearings 20 is disposed on both sides in the axial direction Da of the motor 14. Each radial magnetic bearing 20 has a yoke 21 and a plurality of radial magnetic bearing coils 22.

[0041] ​​The yoke 21 is configured by laminating a plurality of laminated steel sheets in the axial direction Da. The yoke 21 has a back yoke 21a and a plurality of teeth 21b. The back yoke 21a is in a circular ring shape centered on the axis O. The back yoke 21a is fixed to the housing 10. The teeth 21b are provided at equal intervals in the circumferential direction Dc. Each tooth 21b extends from the back yoke 21a toward the inner side in the radial direction Dr. The end portion of each tooth 21b on the inner side in the radial direction Dr opposes the outer peripheral surface of the rotating shaft 11 at intervals in the radial direction Dr.

[0042] The radial magnetic bearing coil 22 is wound around the plurality of teeth 21b. The radial magnetic bearing coil 22 generates a magnetic field by supplying a current from a power source not shown in accordance with a control signal from a bearing control device 60 described later. The radial magnetic bearing 20 restricts movement of the rotating shaft 11 in the radial direction Dr by the magnetic field generated by the radial magnetic bearing coil 22 and supports the rotating shaft 11 in a non-contact manner so as to be rotatable about the circumferential direction Dc around the axis O. The radial magnetic bearing 20 supports the rotating shaft 11 in such a manner that the rotating shaft 11 returns to a reference position in the radial direction Dr in accordance with position information of the rotating shaft 11 detected by a displacement sensor not shown.

[0043] The thrust magnetic bearing 30 has a pair of electromagnets 31 disposed on both sides in the axial direction Da with respect to the thrust ring 18 of the rotating shaft 11. Each electromagnet 31 has a stator 32 and a coil 33.

[0044] The stator 32 is fixed integrally to the housing 10. The stator 32 is formed in a circular ring shape extending in the circumferential direction Dc around the axis O. The stator 32 has a coil holding groove 32m at a position opposite the thrust ring 18 in the axial direction Da. The coil holding groove 32m is recessed in the axial direction Da in a direction away from the thrust ring 18. The coil holding groove 32m is formed in a circular ring shape extending in the circumferential direction Dc around the axis O.

[0045] The coil 33 is housed in the coil holding groove 32m. The coil 33 is formed in a circular ring shape extending in the circumferential direction Dc around the axis O. The coil 33 is integrally formed in a circular ring shape of a metal material.

[0046] Each coil 33 generates a magnetic field by supplying current based on a control signal from a bearing control device 60, described later. The pair of electromagnets 31 of the thrust magnetic bearing 30 generate a magnetic field in each coil 33 that attracts the thrust collar 18 in the axial direction Da. The thrust magnetic bearing 30 attracts the thrust collar 18 by the pair of electromagnets 31, thereby supporting the rotating shaft 11 in a non-contact manner, restricting displacement of the rotating shaft 11 in the axial direction Da of the rotating shaft 11 and allowing the rotating shaft 11 to rotate freely in a circumferential direction Dc about the axis O. The thrust magnetic bearing 30 supports the rotating shaft 11 in a non-contact manner from the axial direction Da, based on position information of the rotating shaft 11 in the axial direction Da detected by a position sensor (not shown), so that the rotating shaft 11 is positioned at a predetermined position in the axial direction Da.

[0047] The bearing control device 60 controls the operation of each radial magnetic bearing 20 and the thrust magnetic bearing 30 of the magnetic bearing device 19 .

[0048] like Figure 2 As shown, the bearing control device 60 is a computer including a processor 61, a ROM 62 (Read Only Memory), a RAM 63 (Random Access Memory), a storage device 64, and a signal receiving module 65. The signal receiving module 65 receives a position signal from a position sensor (not shown) for detecting the position of the rotating shaft 11, a detection signal of the current flowing through the coil 33, and the like.

[0049] like Figure 3 As shown, the bearing control device 60 functionally includes a radial magnetic bearing control unit 70A that controls the operation of the radial magnetic bearing 20 and a thrust bearing control unit 70B that controls the operation of the thrust magnetic bearing 30 .

[0050] Upon receiving a position signal indicating position information in the radial direction Dr of the rotating shaft 11, detected by a displacement sensor (not shown), the radial magnetic bearing control unit 70A controls the current supplied to the radial magnetic bearing coil 22. Furthermore, the yoke 21 of the radial magnetic bearing 20 is made of laminated steel plates. The laminated steel plates are formed by laminating thin steel plates along the axial direction Da. In a radial magnetic bearing 20 having a yoke 21 made of such laminated steel plates, eddy currents are less likely to be generated. Therefore, in this embodiment of the present invention, the radial magnetic bearing control unit 70A does not include a filter 74 like the thrust bearing control unit 70B described later.

[0051] like Figure 4 As shown, the thrust bearing control unit 70B functionally includes a controller 71 , a power amplifier 72 , a current value acquisition unit 73 , and a filter 74 .

[0052] Upon receiving a position command signal indicating position information in the axial direction Da of the rotating shaft 11 detected by a displacement sensor (not shown), the controller 71 outputs a command signal S1 for the current value supplied to the coils 33 of the pair of electromagnets 31 .

[0053] The power amplifier 72 supplies current to the coil 33 based on a command signal S1 output from the controller 71 and a correction signal S2 indicating a correction current value Ih output from a filter 74 described later.

[0054] The current value acquisition unit 73 acquires the coil current value Ic, which is the value of the current actually flowing through the coil 33 .

[0055] The filter 74 corrects the coil current value Ic acquired by the current value acquisition unit 73 based on the influence of the eddy current caused by the magnetic flux generated by the coil 33. The filter 74 outputs the corrected current value Ih generated by correcting the coil current value Ic based on the influence of the eddy current.

[0056] Figure 5 3 is a diagram showing an equivalent circuit of the coil 33 of the electromagnet 31. Figure 5 As shown, the electromagnet 31 generates eddy currents around the magnetic flux generated by the current flowing through the coil 33. The influence of these eddy currents can be modeled as a Cauer trapezoidal model that appears multiple times in the form of a first-order eddy current (primary), a second-order eddy current (secondary) generated by the first-order eddy current, and so on. Therefore, the sum of the influences caused by these multiple eddy currents is expressed as the term Z generated by the influence of the eddy currents. ed To express.

[0057] The filter 74 corrects the coil current value Ic based on the impedance of the electromagnet 31 , the resistance of the coil 33 , and the inductance of the coil 33 , and based on the influence of the eddy current, and generates a corrected current value.

[0058] More specifically, for the voltage V applied to the coil 33 i The response ratio of the value of the main excitation current I1 is I1 / V i The resistance R0 of the coil 33, the inductance L0 of the coil 33, the Laplace operator s, and the term Z due to the influence of the eddy current ed The relationship shown in the following formula (3) holds between them.

[0059] [Formula 2]

[0060]

[0061] Based on the above formula (3), by presetting the term Z generated by the influence of eddy current ed , the filter 74 can calculate the value I1 of the main excitation current and output the value I1 as the correction current value.

[0062] Here, the term Z generated by the eddy current is used to ed A setting method S10 of the bearing control device 60 that is set in advance in the filter 74 will be described.

[0063] like Figure 6 As shown, the setting method S10 of the bearing control device 60 includes step S11 of obtaining the impedance of the electromagnet, step S12 of obtaining the term generated by the influence of eddy current, step S13 of fitting the term generated by the influence of eddy current, and step S14 of setting the term generated by the influence of eddy current in the filter.

[0064] In the step S11 of obtaining the impedance of the electromagnet, the impedance I of the electromagnet 31 is obtained. r / V i To this end, the impedance I of the electromagnet 31 can be actually measured. r / V i , the impedance I of the electromagnet 31 can also be calculated by magnetic field analysis r / V i .

[0065] In the step S12 of obtaining the term due to the influence of the eddy current, the term Z due to the influence of the eddy current is estimated according to the following equation (4): ed Here, the resistance R0 of the coil 33 and the static inductance L0 of the coil 33 can be measured in practice or calculated by analysis. Here, the static inductance L0 of the coil 33 is the inductance related to the main magnetic flux of the coil 33 that contributes to the attraction of the coil 33, and is highly dependent on the gap between the electromagnet 31 and the thrust ring 18. On the other hand, the term Z generated by the influence of eddy current ed This is a term generated by the structure of the electromagnet 31 and is less dependent on the gap between the electromagnet 31 and the thrust ring 18 .

[0066] [Formula 3]

[0067]

[0068] When Tz and Tp are set as time constants, in step S13 of fitting the term generated by the influence of eddy current, the term Z generated by the influence of eddy current is calculated according to the frequency of the rotating shaft 11 and the following equation (5). ed Here, in the rotating machine 1, when the frequency of the rotating shaft 11 is set to 10 to 1000 Hz, for example, the term Z generated by the influence of eddy current is actually measured. ed The magnitude of the phase distortion and the magnitude of the gain (the inverse of the impedance) are respectively calculated by the least square method, and the term Z generated by the influence of the eddy current is converted to ed Fitting to a value close to the preset ideal value.

[0069] Z ed = Π {(1 + Tz * s) / (1 + Tp * s)}... (5)

[0070] In the step S14 of setting the term Zed resulting from the influence of eddy current to the filter, the term Zed resulting from the influence of eddy current fitted in the step S13 is set to the filter 74. ed to the filter 74.

[0071] (EFFECTS)

[0072] According to the bearing control device 60, the magnetic bearing device 19, the rotating machine 1, and the setting method S10 of the magnetic bearing device 19 of the above-described structure, the correction current value corrected according to the influence of eddy current resulting from the magnetic flux generated by the coil 33 is generated by the filter 74. In the power amplifier 72, the current command value based on the correction current value is inputted, and the current is supplied to the coil 33, whereby the influence caused by the eddy current generated in the coil 33 can be suppressed. Therefore, the generation of the magnetic flux in the coil 33 is suppressed by the eddy current, and the decrease of the magnetomotive force in the coil 33 is suppressed. As a result, the bearing performance of the thrust magnetic bearing 30 can be improved.

[0073] Further, the filter 74 corrects the coil current value Ic according to the impedance I r V i of the electromagnet 31, the resistance R0 of the coil 33, and the inductance L0 of the coil 33, and thereby the correction current value is generated by the coil 33 in such a manner that the influence of eddy current is canceled by exciting the coil 33.

[0074] Further, in the thrust magnetic bearing 30 provided with the coil 33 integrally formed of metal, the influence caused by the eddy current generated in the coil 33 becomes large. Therefore, by suppressing the influence caused by the eddy current generated in such a coil 33, the bearing performance can be more effectively improved.

[0075] (OTHER EMBODIMENTS)

[0076] The above-described embodiment of the present application has been described in detail with reference to the drawings, but the specific structure is not limited to the embodiment, and design changes and the like within the scope of the gist of the present application are included.

[0077] Further, in the above-described embodiment, the flow of the setting method of the term Zed resulting from the influence of eddy current is described, but the step can be appropriately changed.

[0078] <POSTSCRIPT>

[0079] The bearing control device 60, the magnetic bearing device 19, the rotating machine 1, and the setting method S10 of the magnetic bearing device 19 described in the embodiments can be grasped as follows, for example.

[0080] (1) The bearing control device 60 according to the first aspect is a bearing control device 60 of a magnetic bearing 30 that includes an electromagnet 31 including a coil 33 disposed in opposition to a rotating shaft 11 extending in an axial direction Da, and that supports the rotating shaft 11 in a non-contact manner so as to be rotatable in a circumferential direction Dc around an axis O by a magnetic field generated by a current flowing through the coil 33. The bearing control device 60 includes a current value acquisition section 73 that acquires a value of the current flowing through the coil 33, that is, a coil current value Ic; a filter 74 that generates a corrected current value that corrects the coil current value Ic acquired by the current value acquisition section 73 according to an influence of eddy current generated by a magnetic flux generated by the coil 33; and a power amplifier 72 that supplies a current to the coil 33 with a current command value based on the corrected current value as input

[0081] The bearing control device 60 generates a corrected current value that is corrected according to an influence of eddy current generated by a magnetic flux generated by the coil 33 by the filter 74. In the power amplifier 72, a current is supplied to the coil 33 with a current command value based on the corrected current value as input, whereby it is possible to suppress the influence of eddy current generated in the coil 33. Therefore, the generation of the magnetic flux in the coil 33 is suppressed by the eddy current, and the decrease in the magnetomotive force in the coil 33 is suppressed. As a result, it is possible to improve the bearing performance of the magnetic bearing 30.

[0082] (2) The bearing control device 60 according to the second aspect is the bearing control device 60 according to (1), in which the filter 74 generates the corrected current value according to an influence of the eddy current based on an impedance I r / V i of the electromagnet 31, a resistance R0 of the coil 33, and an inductance L0 of the coil 33, and corrects the coil current value Ic according to the influence of the eddy current.

[0083] Accordingly, the filter 74 corrects the coil current value Ic according to an influence of the eddy current based on the impedance I r / V i of the electromagnet 31, the resistance R0 of the coil 33, and the inductance L0 of the coil 33, whereby the corrected current value is generated in the coil 33 in such a manner that the influence of the eddy current is canceled by excitation.

[0084] (3) The bearing control device 60 according to the third aspect is the bearing control device 60 according to (2), in which the voltage applied to the electromagnet 31 is set to V iThe resistance of the coil 33 is set to R0, the inductance of the coil 33 is set to L0, the Laplace operator is set to s, and the term Z ed The filter 74 obtains a current value I1 obtained according to the following formula (6) as the correction current value.

[0085] [Formula 4]

[0086]

[0087] Thus, the correction current value can be obtained in a manner that excitation by the coil 33 is performed while the influence of the eddy current is canceled.

[0088] (4) The bearing control device 60 according to the fourth aspect is the bearing control device 60 according to the third aspect, wherein, when Tz and Tp are set as time constants, the filter 74 obtains a term Z r / V i caused by the influence of the eddy current calculated according to the following formula (7) representing the impedance I ed of the electromagnet by fitting according to a frequency range when the rotating shaft 11 rotates.

[0089] [Formula 5]

[0090]

[0091] Z ed = Π {(1 + Tz * s) / (1 + Tp * s)}... (8)

[0092] Thus, the correction current value can be generated in a manner that excitation by the coil 33 is performed while the influence of the eddy current is canceled in the frequency range when the rotating shaft 11 rotates.

[0093] (5) The magnetic bearing device 19 according to the fifth aspect includes the magnetic bearing 30 having the electromagnet 31 including the coil 33 disposed in opposition to the rotating shaft 11 extending in the axial direction Da, and supporting the rotating shaft 11 in a non-contact manner so as to be rotatable in the circumferential direction Dc around the axis O by a magnetic field generated due to a current flowing through the coil 33, and any one of the bearing control devices 60 according to the first to fifth aspects.

[0094] Thus, the magnetic bearing device 19 having the bearing control device 60 capable of suppressing the influence caused by the eddy current generated in the coil 33 and improving the bearing performance can be provided.

[0095] (6) The magnetic bearing device 19 according to the sixth aspect is the magnetic bearing device 19 according to the fifth aspect, wherein the magnetic bearing 30 is a thrust magnetic bearing 30 that restricts displacement of the rotating shaft 11 in the axial direction Da and supports the rotating shaft 11 in a non-contact manner so as to be free to rotate in the circumferential direction Dc around the axis O.

[0096] Thus, in the thrust magnetic bearing 30, it is possible to suppress the influence caused by the eddy current generated in the coil 33 and improve the bearing performance.

[0097] (7) The magnetic bearing device 19 according to the seventh aspect is the magnetic bearing device 19 according to the fifth or sixth aspect, wherein the coil 33 is formed integrally of metal, is disposed on the outer side in the radial direction Dr with the axial direction Da as the center with respect to the rotating shaft 11, and is formed in a ring shape extending along the circumferential direction Dc with the axial direction Da as the center.

[0098] Thus, in the coil 33 formed integrally of metal, the influence caused by the eddy current generated in the coil 33 is large. Therefore, by suppressing the influence caused by the eddy current generated in such a coil 33, it is possible to more effectively improve the bearing performance.

[0099] (8) The rotating machine 1 according to the eighth aspect includes the rotating shaft 11 extending in the axial direction Da and the magnetic bearing device 19 according to any one of the first to seventh aspects.

[0100] Examples of the rotating machine 1 include a turbomachine, a steam turbine, a gas turbine, a centrifugal compressor, and the like.

[0101] Thus, it is possible to provide the rotating machine 1 that includes the magnetic bearing device 19 capable of suppressing the influence caused by the eddy current generated in the coil 33 and improving the bearing performance.

[0102] (9) The setting method S10 of the bearing control device 60 according to the ninth aspect is the setting method S10 of the bearing control device 60 according to any one of the first to fourth aspects, including: a step S11 of acquiring the impedance I of the electromagnet 31 r i ; a step S12 of acquiring a term Z caused by the influence of the eddy current calculated according to the following formula (9) when the resistance of the coil 33 is set to R0 and the inductance of the coil 33 is set to L0 ed ; a step S13 of fitting the term Z caused by the influence of the eddy current according to the frequency range when the rotating shaft 11 rotates and according to the following formula (10) when Tz and Tp are set to time constants ed ; and a step S14 of setting the filter 74 according to the fitted term Z caused by the influence of the eddy current ed .​

[0103] [Formula 6]

[0104]

[0105] Z ed = Π{(1 + Tz*s) / (1 + Tp*s)}... (10)

[0106] Thus, the bearing control device 60 having the filter 74 capable of suppressing the influence caused by the eddy current generated in the coil 33 and improving the bearing performance can be set.

[0107] Industrial applicability

[0108] According to the above-described one mode, the influence caused by the eddy current generated in the coil can be suppressed, and the bearing performance can be improved.

[0109] Symbol explanation

[0110] 1 - rotating machine, 10 - housing, 11 - rotating shaft, 12 - first impeller, 13 - second impeller, 14 - motor, 15 - rotor core, 16 - stator, 18 - thrust ring, 19 - magnetic bearing device, 20 - radial magnetic bearing, 21 - yoke, 21a - back yoke, 21b - tooth, 22 - radial magnetic bearing coil, 30 - magnetic bearing, 30 - thrust magnetic bearing, 31 - electromagnet, 32 - stator, 32m - coil holding slot, 33 - coil, 60 - bearing control device, 61 - processor, 62 - ROM, 63 - RAM, 64 - storage device, 65 - signal receiving module, 70A - radial magnetic bearing control section, 70B - thrust bearing control section, 71 - controller, 72 - power amplifier, 73 - current value acquisition section, 74 - filter, Da - axial direction, Dc - circumferential direction, Dr - radial direction, O - axial line, S1 - command signal, S2 - correction signal.

Claims

1. A bearing control device that is a bearing control device of a magnetic bearing that has an electromagnet including a coil disposed in opposition to a rotating shaft extending in an axial direction, and supports the rotating shaft in a noncontact manner so as to be free to rotate in a circumferential direction around the axis by a magnetic field generated due to current flowing through the coil, the bearing control device comprising: a current value acquisition section that acquires a value of the current flowing through the coil, that is, a coil current value; a filter that generates a corrected current value that corrects the coil current value acquired by the current value acquisition section according to an influence of eddy current generated by magnetic flux generated by the coil; and a power amplifier that supplies current to the coil with a current command value based on the corrected current value as input.

2. The bearing control device according to claim 1, wherein the filter generates the corrected current value that corrects the coil current value according to the influence of the eddy current according to an impedance of the electromagnet and a resistance of the coil and an inductance of the coil.

3. The bearing control device according to claim 2, wherein [Mathematical expression 1] Ic = I0 + Keddy I0 4. The bearing control device according to claim 3, wherein [Mathematical expression 2] Keddy = 2π2f2μ0R2 5. A magnetic bearing device comprising: a magnetic bearing that has an electromagnet including a coil disposed in opposition to a rotating shaft extending in an axial direction, and supports the rotating shaft in a noncontact manner so as to be free to rotate in a circumferential direction around the axis by a magnetic field generated due to current flowing through the coil; and the bearing control device according to claim 1 or 2.

6. The magnetic bearing device according to claim 5, wherein the magnetic bearing is a thrust magnetic bearing that restricts displacement of the rotating shaft in the axial direction and supports the rotating shaft in a noncontact manner so as to be free to rotate in the circumferential direction around the axis.

7. The magnetic bearing device according to claim 5, wherein the coil is formed of metal in one piece, is disposed on an outer side in a radial direction with respect to the rotating shaft centered on the axial direction, and is formed in a ring shape extending in a circumferential direction centered on the axial direction.

8. A rotating machine comprising: a rotating shaft extending in an axial direction; and the magnetic bearing device according to claim 5. when a voltage applied to the coil is set as V i , an electric resistance of the coil is set as R0, an inductance of the coil is set as L0, a Laplacian operator is set as s, and a term generated due to an influence of the eddy current is set as Z ed , the filter obtains a current value I1 obtained according to the following formula (1) as the correction current value, 9. A setting method of a bearing control device that is a setting method of the bearing control device according to claim 1 or 2, the method comprising the following step: [Mathematical expression 3] Keddy = 2π2f2μ0R2 ​ When Tz, Tp are set as time constants, the filter obtains a term Z r / V i that is generated by the influence of the eddy current, calculated from the following equation (2) representing the impedance I ed of the electromagnet, by fitting based on the following equation (3) according to the frequency range when the rotation axis is rotated ​ Z ed =Π{(1+Tz*s) / (1+Tp*s)}……(3)。 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ obtaining the impedance I of the electromagnet r / V i ; When the resistance of the coil is set to R0 and the inductance of the coil is set to L0, a term Z due to the influence of the eddy current calculated according to the following equation (4) is obtained ed ; When Tz, Tp are set as time constants, according to the frequency range when the rotation axis rotates, and according to the following formula (5), the term Z ed is fitted; and According to the fitted term Z generated as a result of the influence of the vortex flow ed , the filter is set, ​ Z ed = Π{(1 + Tz*s) / (1 + Tp*s)} … (5).

Images