Suspension levitation type ac motor

Abstract

To provide a suspension levitation type AC motor having a simple configuration or drive control, in which a rotor disposed at a lower side of a stator is stably rotated in hollow.SOLUTION: A suspension levitation type AC motor comprises: a stator in which n×m pieces ((n) is an integer equal to or greater than 3 and (m) is an integer equal to or greater than 1) of electromagnets each including a plurality of electromagnet cores are arrayed in a circumferential direction on a plane orthogonal to a gravity axis; a rotor in which multiple floating body cores are arrayed radially and which is rotated in follow by a suction force in a gravity axis direction generated between the floating body cores and the electromagnet cores and torque around the gravity axis; and a control circuit for generating an n-phase AC voltage signal to be applied to the electromagnets. The n-phase AC voltage signal is generated as a signal obtained by superposing a rotation signal, which is set based on a rotation frequency corresponding to a target rotation speed of the rotor with respect to the stator, on a floatation signal, which is set based on a floatation frequency for maintaining a gap of the rotor with respect to the stator, by AM modulation.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a suspended AC motor in which a rotor, disposed below a stator, rotates in midair due to an attractive force in the direction of the gravity axis and a rotational force about the gravity axis generated between the rotor and the stator. [Background technology]

[0002] There is known an electrostatically levitated synchronous motor that includes a stator in which a conductor pattern is formed on an insulating disk, and a rotor that is disposed below and facing the stator (see, for example, Patent Document 1). Such a synchronous motor is provided with a levitation electrode and a rotation electrode, and the rotor is levitated by applying a levitation voltage to the levitation electrode, and the rotor is rotated by applying a rotation voltage to the rotation electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-261976 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional synchronous motors, the gap between the stator and rotor is detected by a displacement sensor, and the levitation voltage applied to the levitation electrode is controlled according to the detected value, thereby maintaining the gap within a certain range. The rotor is rotated by applying a rotation drive voltage, which is generated separately from the levitation voltage, to a rotation electrode provided separately from the levitation electrode. Such synchronous motors have a complex motor structure, and therefore the circuit configuration and drive control for levitation and rotation are also complex.

[0005] The present invention has been made to solve these problems, and provides a suspended AC motor that has a simple structure and drive control, and in which a rotor arranged below a stator rotates stably in mid-air due to the suction force in the direction of the gravity axis and the rotational force around the gravity axis generated between the rotor and the stator. [Means for solving the problem]

[0006] A suspended levitation type AC motor in a specific embodiment of the present invention comprises a stator in which n × m electromagnets (n is an integer of 3 or more, m is an integer of 1 or more) each having a plurality of electromagnet cores are arranged circumferentially in a plane perpendicular to the axis of gravity, a rotor in which a plurality of levitation body cores are arranged radially and which rotates in midair by an attractive force in the gravity axis direction and a rotational force about the gravity axis generated between the plurality of levitation body cores and the plurality of electromagnet cores, and a control circuit which generates an n-phase AC voltage signal to be applied to the electromagnets, the n-phase AC voltage signal being generated as a signal obtained by superimposing, by AM modulation, a levitation signal set based on a levitation frequency for maintaining a gap between the rotor and the stator, and a rotation signal set based on a rotational frequency corresponding to a target rotational speed of the rotor relative to the stator. Effect of the Invention

[0007] According to the present invention, it is possible to provide a suspended AC motor which has a simple structure and drive control, and in which a rotor disposed below a stator rotates stably in the air. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a state in which a suspended levitation type AC motor according to an embodiment of the present invention is observed from the side. [Diagram 2] FIG. 2 is a diagram showing a state in which a stator is observed from the opposing rotor side. [Diagram 3] FIG. 2 is a diagram showing an overhead view of one of the electromagnets. [Figure 4] FIG. 2 is a diagram showing a rotor observed from the opposing stator side. [Diagram 5]FIG. 4 is a diagram for explaining the formation of a magnetic path. [Figure 6] 4 is a diagram for explaining the relationship between an electromagnet core of each phase and a levitator core. FIG. [Figure 7] FIG. 2 is a diagram showing a control circuit of a suspended AC motor. [Figure 8] FIG. 4 is a diagram for explaining the relationship between a levitation frequency and a resonance frequency. [Figure 9] FIG. 4 is a diagram showing AC voltage signals applied to each phase in the first embodiment. [Figure 10] FIG. 11 is a diagram showing AC voltage signals applied to each phase in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiments of the present invention will be described with reference to the attached drawings. When there are multiple structures having the same or similar configurations in each drawing, in order to avoid complication, some of the structures may be given reference symbols and the same reference symbols may not be given to the other structures. Note that the invention according to the claims is not limited to the following embodiments. Also, not all of the configurations described in the embodiments are necessarily essential as means for solving the problem.

[0010] FIG. 1 is a schematic diagram showing a suspended AC motor 100 according to this embodiment (hereinafter, referred to as "AC motor 100") as viewed from the side. Specifically, it is a diagram showing the AC motor 100 installed on a horizontal floor surface as viewed from a direction perpendicular to the direction of gravity. In this embodiment, as shown by the coordinate axes in the figure, the direction of gravity is the positive Z-axis, and two axes perpendicular to each other in the horizontal plane are the X-axis and Y-axis directions. In the subsequent drawings, similar coordinate axes based on the state in which the AC motor 100 is installed as in FIG. 1 are also shown to indicate the orientation of the structure shown in each drawing.

[0011] In the AC motor 100 according to this embodiment, the rotor 300 disposed below the stator 200 rotates in midair due to the attractive force in the gravity axis direction (Z-axis direction) and the rotational force around the gravity axis (Z-axis) generated between the rotor 300 and the stator 200. The figure shows the AC motor 100 during rotational driving, and more specifically, the rotor 300 is spaced from the stator 200 by a gap Z. g The figure shows the rotor 300 rotating without contact with the surrounding environment, with a gap Z between the rotor 300 and the stator 200. Although the figure shows the rotor 300 rotating idly, if a power transmission mechanism or the like is connected to the rotor 300, the rotational motion can be used as power. In the AC motor 100 according to this embodiment, the rotor 300 rotates with respect to the stator 200 at a gap Z by balancing the attractive force from the stator 200 and gravity. g The rotor 300 is a suspended levitation motor that is suspended in midair with a gap of 0.05 mm between the rotor 300 and the stator 200. Although the rotor 300 is not suspended above the stator 200, the term "levitation" may be used in the following description to mean that the rotor 300 is suspended in midair.

[0012] As described above, in the AC motor 100, the rotor 300 disposed below the stator 200 rotates in midair, and therefore the stator 200 is also suspended and supported by a structure. In this embodiment, the stator 200 is suspended via a plurality of suspension dampers 530 from a top plate 520 supported by a plurality of supports 510 erected on a floor surface. The suspension dampers 520 function to suppress vibration of the stator 200 that occurs as the rotor 300 rotates. By suppressing the vibration of the stator 200, the rotation of the rotor 300 becomes more stable.

[0013] The rotor 300 includes a rotor base 310, which is, for example, an aluminum disk, and a plurality of levitation body cores 321 arranged on the rotor base 310, which will be described in detail later. The stator 200 includes a stator base 210, which is, for example, an aluminum disk, and a plurality of electromagnets 220 arranged on the stator base 210, which will be described in detail later. An AC voltage signal to be applied to each of the electromagnets 220 is generated by a control circuit 400. The control circuit 400 is installed on the upper surface of the top plate 520, and is electrically connected to each of the electromagnets 220 via cables (not shown). The AC voltage signal generated by the control circuit 400 is applied to each of the electromagnets 220 via the cables.

[0014] 2 is a diagram showing the stator 200 observed from the side of the rotor 300 opposed to the stator 200 in FIG. 1. The AC motor 100 in this embodiment includes nine electromagnets 220 arranged on concentric circles along the circumferential direction on the surface of a stator base 210, which is a plane perpendicular to the axis of gravity. As shown in the figure, the centers of the concentric circles are C s Let us assume that.

[0015] Specifically, the nine electromagnets 220 are electromagnets EM1 to EM9 arranged in order in a clockwise direction, and the electromagnets EM1, EM4, and EM7 are classified into a first phase (Phase 1) group to which a first AC voltage signal is applied, the electromagnets EM2, EM5, and EM8 are classified into a second phase (Phase 2) group to which a second AC voltage signal is applied, and the electromagnets EM3, EM6, and EM9 are classified into a third phase (Phase 3) group to which a third AC voltage signal is applied. In other words, three electromagnets 220 (m=3) per phase are arranged for three phases (n=3), for a total of nine (=3×3) electromagnets 220, and are arranged in a clockwise order in the C s At this time, the electromagnets 220 adjacent to each other are arranged along the circumferential direction of a circle having the center C s It forms an angle of 40° with respect to

[0016] Each electromagnet 220 has a center C sThe electromagnet 220 includes six electromagnet cores 221 arranged along the radial direction with respect to the stator base 210, and a bobbin 222 that bundles and supports these electromagnet cores 221. The bobbin 222 also functions as a fixing part that fixes the electromagnet 220 to the stator base 210. The adjacent electromagnet cores 221 are spaced apart from each other by a center C s It forms an angle of 4.8° with respect to

[0017] An adjustment magnet 230 is installed in the center of the stator base 210. The adjustment magnet 230 is a permanent magnet, and the specific function thereof will be described later.

[0018] 3 is a diagram showing an overhead view of one of the electromagnets 220. As described above, one electromagnet 220 includes six electromagnet cores 221, and each electromagnet core 221 is formed by laminating, for example, ten steel plates. Each electromagnet core 221 is an E-shaped core having a center leg around which a coil 223 is wound. The coil 223 is wound so as to surround the center leg of the six electromagnet cores 221 via the bobbin 222, and an AC voltage signal according to the phase is applied by the control circuit 400.

[0019] The bobbin 222 aligns and supports the six electromagnet cores 221, tightly winds the coil 223, and also functions as a fixing portion that fixes the electromagnet 220 to the stator base 210. The four fixing holes 222a shown in the figure are used to screw the bobbin 222 to the stator base 210.

[0020] 4 is a diagram showing the rotor 300 observed from the side of the stator 200 facing in FIG. 1. The AC motor 100 in this embodiment includes a large number of I-shaped floater cores 321 arranged radially on the surface of the rotor base 310, which is a plane perpendicular to the axis of gravity. Specifically, the floater cores 321 adjacent to each other are aligned with each other at the center C of the stator base 210. s The center C is the point opposite to R4.8° with respect to the axis of the magnet 221, and a total of 75 levitator cores 321 are arranged. Each levitator core 321 is formed, like the electromagnet core 221, by laminating, for example, ten steel plates.

[0021] The inner peripheral end of the levitator core 321 is fixed to the rotor base 310 by an inner frame 341, and the outer peripheral end is fixed to the rotor base 310 by an outer frame 342. An adjustment magnet 330 is provided in the center of the rotor base 310. The adjustment magnet 330 is a permanent magnet, and is provided so as to act with the adjustment magnet 230 provided on the stator base 210 to exert a repulsive or attractive force on each other.

[0022] Even when an adjusted AC voltage signal is applied to each electromagnet 220 as described below, the gap Z between the stator 200 and the rotor 300 may vary due to individual differences in the electromagnets 220. g In such a case, the adjustment magnet 230 and the adjustment magnet 330 are used to offset the difference. g differs from the expected value, adjustment magnets 230 and 330 that are expected to have a repulsive or attractive force that cancels out the difference are selected and attached to stator base 210 and rotor base 310, respectively. Therefore, it is desirable that stator base 210 and rotor base 310 are configured so that adjustment magnets 230 and 330, respectively, can be attached and detached interchangeably.

[0023] 5 is a diagram for explaining a magnetic path that is formed when an AC voltage signal is applied to coil 223. Specifically, the diagram illustrates a pair of electromagnet core 221 and levitator core 321 that face each other.

[0024] When an AC voltage signal is applied to the core 321, a current C R As a result, two closed magnetic circuits M are formed between the E-shaped electromagnet core 221 and the I-shaped levitator core 321 as shown by the dotted lines.R1 , M R2 At this time, a force acts on the electromagnet core 221 to attract the levitation body core 321 in the direction of the gravity axis, but since the rotor 300 has a considerable mass, the attractive force on the rotor 300 and the gravity are balanced, and the rotor 300 forms a gap Z with respect to the stator 200. g They float in mid-air with a gap of .

[0025] 6 is a diagram for explaining the relationship between the electromagnet cores 221 of each phase and the levitator core 321. Specifically, the diagram shows three of each of the electromagnet cores 221 belonging to the first phase (Phase 1), the second phase (Phase 2), the third phase (Phase 3), and the first phase (Phase 1) that are adjacent to each other, and arranged in a line. For each of the extracted electromagnet cores 221, the levitator cores 321 that face the electromagnet cores nearby are also shown.

[0026] As described above, adjacent electromagnets 220 form an angle of 40° around the rotation axis of AC motor 100. As shown in the figure, when electromagnet cores 221 belonging to the first phase (Phase 1) face the corresponding levitation body cores 321 without any deviation, electromagnet cores 221 belonging to the second phase (Phase 2) are deviated from the corresponding levitation body cores 321 by 1.6° around the rotation axis, and similarly, electromagnet cores 221 belonging to the third phase (Phase 3) are deviated from the corresponding levitation body cores 321 by 3.2°.

[0027] In this state, when the voltage applied to the electromagnet 220 of the second phase (Phase 2) is made stronger than the voltage applied to the electromagnet 220 of the first phase (Phase 1) and the electromagnet 220 of the third phase (Phase 3), the force of attraction between the electromagnet core 221 of the second phase (Phase 2) and the corresponding levitation body core 321 to eliminate the misalignment between them becomes dominant, and as a result, the rotor 300 rotates by 1.6°. Then, the electromagnet cores 221 belonging to the second phase (Phase 2) face the corresponding levitation body cores 321 without any misalignment, and the electromagnet cores 221 belonging to the third phase (Phase 3) are misaligned with the corresponding levitation body cores 321 by 1.6° around the rotation axis. In this state, if the voltage applied to the third-phase (Phase3) electromagnet 220 is made stronger than the voltage applied to the first-phase (Phase1) electromagnet 220 and the second-phase (Phase2) electromagnet 220, the force of attraction between the third-phase (Phase3) electromagnet core 221 and the corresponding levitator core 321 to eliminate the mutual misalignment becomes dominant, and the rotor 300 rotates by a further 1.6°. Based on this principle, by sequentially varying the voltages applied to the electromagnets 220 of each phase, the rotor 300 can be rotated continuously and stably in one direction.

[0028] 7 is a diagram showing a control circuit 140 of the AC motor 100. As shown in the figure, one end of the coil 223 wound around each electromagnet 220 is grounded via a capacitor 241, and the other end is connected to a power source corresponding to the phase to which it belongs.

[0029] Specifically, the coils 223 of electromagnets EM1, EM4, and EM7 belonging to the first phase (Phase1) are connected to capacitors C1, C4, and C7, respectively, and are grounded, and are also connected to a common power source, a first AC power source 421. Similarly, the coils 223 of electromagnets EM2, EM5, and EM8 belonging to the second phase (Phase2) are connected to capacitors C2, C5, and C8, respectively, and are grounded, and are also connected to a common power source, a second AC power source 422, and the coils 223 of electromagnets EM3, EM6, and EM9 belonging to the third phase (Phase3) are connected to capacitors C3, C6, and C9, respectively, and are grounded, and are also connected to a common power source, a third AC power source 423.

[0030] The first AC power supply 421, the second AC power supply 422, the third AC power supply 423, and the modulation synchronization circuit 410 are included in the control circuit 400. The first AC power supply 421 outputs a first-phase AC voltage signal V P1 Similarly, the second AC power supply 422 applies a second phase AC voltage signal V P2 The third AC power supply 423 applies a third-phase AC voltage signal V P3 In response to a control signal from the modulation synchronization circuit 410, the first AC power source 421, the second AC power source 422, and the third AC power source 423 apply a first-phase AC voltage signal V P1 (t), second phase AC voltage signal V P2 (t), the third phase AC voltage signal V P3 Output (t).

[0031] Figure 8 shows the levitation frequency f d and the resonance frequency f0. i (i is an integer from 1 to 9) and the inductance L of the electromagnet EM i A capacitor C connected to i The capacitance C of the magnet is assumed to be the same regardless of i in design. The inductance L is calculated by dividing the magnetic permeability of a vacuum by μ0 and the magnetic permeability of an electromagnet EMi The number of turns of coil 223 is N, and the electromagnet EM i Let S be the total effective cross-sectional area of ​​the electromagnet cores 221 constituting the levitator core 321 (ie, the effective cross-sectional area of ​​the magnetic poles) and z0 be the target gap between the electromagnet cores 221 and the levitator core 321, then this is expressed by the following formula (1).

number

[0032] The resonance frequency f0 is expressed by the following equation (2) using the inductance L and capacitance C.

number

[0033] 8 shows the admittance characteristic at the resonance frequency f0. As shown in the figure, the admittance reaches a maximum value y0 at the resonance frequency. For the resonance frequency f0 calculated in this way, the levitation frequency f for maintaining the gap between the rotor 300 and the stator 200 is d It is advisable to set the levitation frequency f to a value slightly larger than the resonance frequency f0. d The AC voltage signal with the set value increases the current to strengthen the attractive force when the gap becomes larger due to a disturbance, and decreases the current to weaken the attractive force when the gap becomes smaller. In other words, it exerts a self-balancing property that tries to maintain the target gap.

[0034] The levitation frequency f d In actual design, it is desirable to set it to a value larger than the resonance frequency f0 and smaller than the upper limit frequency f1 for the value (=y0 / 2) at which the admittance at the resonance frequency f0 is halved. As will be described later in detail, the amplitude value of the AC voltage signal is determined so that the target gap becomes z0, and within this range, it is expected that the gap will return to the target gap z0 smoothly due to self-balancing even if it is affected by disturbance during rotational driving.

[0035] Thus, the levitation frequency f dOnce determined, the levitation frequency f d According to the first phase AC voltage signal V P1 (t), second phase AC voltage signal V P2 (t), the third phase AC voltage signal V P3 In this embodiment, the AC voltage signals are set to the levitation frequency f d A rotation signal determined based on a rotation frequency corresponding to a target rotation speed of the rotor 300 relative to the stator 200 is superimposed by AM modulation on a levitation signal determined based on the target rotation speed of the rotor 300 relative to the stator 200. Specific examples will be described below.

[0036] 9 is a diagram showing the AC voltage signals applied to each phase in Example 1. The vertical axis represents the applied voltage V, and the horizontal axis represents the elapsed time t.

[0037] The first phase AC voltage signal V is shown by a thick solid line. P1 (t), the second phase AC voltage signal V P2 (t), the third-phase AC voltage signal V P3 (t) is expressed by the following formulas (3) to (5). m , A c is the amplitude adjustment value, which determines the maximum and minimum values ​​of the waviness as shown in the figure. m is the rotation frequency that is set according to the target rotation speed of the rotor 300, and t represents the elapsed time.

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[0038] In the above formulas (3) to (5), the components enclosed in curly brackets {} represent rotation signals including DC offset components, and are mainly components for rotating the rotor 300 in accordance with the principle described with reference to Fig. 6. Also, in the above formulas (3) to (5), the components after the curly brackets {} represent levitation signals, and are mainly levitation frequency f d This is a component for maintaining the gap between rotor 300 and stator 200 based on the above formula. As can be seen from both formulas, the AC voltage signal applied to each phase employs AM modulation in which a rotation signal is superimposed on the amplitude of the levitation signal.

[0039] 6, when the electromagnet core 221 belonging to a certain phase faces the levitator core 321, the electromagnet core 221 belonging to the other phase faces the levitator core 321 in a shifted manner, so that the components of the levitation signal not only contribute to maintaining the gap but also contribute to the rotation of the rotor 300. Similarly, the components of the rotation signal not only contribute to the rotation of the rotor 300 but also contribute to maintaining the gap.

[0040] Moreover, the force with which the electromagnet core 221 attracts the levitator core 321 changes depending on the current flowing through the coil 223. In order to levitate the rotor 300 in midair with a target gap z0, it is necessary to balance the force with which the electromagnet core 221 attracts the levitator core 321 with gravity. m , A c is adjusted taking into consideration the resistance value of coil 223, the mass of rotor 300, etc., so that target gap z0 is achieved.

[0041] In the first embodiment, the AC voltage signal is set so that the phase of the rotation signal and the phase of the levitation signal have a phase difference of 2π / 3 between the first and second phases, between the second and third phases, and between the third and first phases. By using such an AC voltage signal, the gap Z gThere is no need to perform feedback control on the levitation signal, and the self-balancing property obtained by the levitation signal allows the rotor 300 to be stably levitated in mid-air relative to the stator 200. In addition, since the rotation signal is superimposed by AM modulation, the rotor 300 can be rotated stably in the AC motor 100 that employs a simple structure without providing separate cores for levitation and rotation.

[0042] 10 is a diagram showing AC voltage signals applied to each phase in Example 2. The vertical axis represents the applied voltage V, and the horizontal axis represents the elapsed time t.

[0043] The first phase AC voltage signal V is shown by a thick solid line. P1 (t), the second phase AC voltage signal V P2 (t), the third-phase AC voltage signal V P3 (t) is expressed by the following formulas (3) to (5). m , A c is the amplitude adjustment value, which determines the maximum and minimum values ​​of the waviness as shown in the figure. m is the rotation frequency that is set according to the target rotation speed of the rotor 300, and t represents the elapsed time.

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[0044] As in the above formulas (3) to (5), in the above formulas (6) to (8), the components enclosed in the curly brackets {} represent the rotation signal including the DC offset component, and the components following the curly brackets {} represent the levitation signal. m , A cis adjusted taking into consideration the resistance value of coil 223 and the like so that the target gap is achieved. As can be seen from both equations, the AC voltage signal applied to each phase employs AM modulation in which the rotation signal is superimposed on the amplitude of the levitation signal.

[0045] In the second embodiment, the AC voltage signals of the respective phases are set so that the phases of the rotation signals have a phase difference of 2π / 3 between the first and second phases, between the second and third phases, and between the third and first phases, respectively, but the phases of the levitation signals match between the first, second, and third phases. By using such AC voltage signals, in addition to the same effects as in the first embodiment, it is possible to obtain an effect that the configuration of the control circuit 400 can be simplified. Furthermore, by comparing the phases of the currents of the respective phases with respect to the applied voltage, that is, from the relative phase differences of the currents of the respective phases, it is possible to estimate the positional relationship between the magnetic poles 221 of the coils of the respective phases and the rotor magnetic poles 321, and it becomes possible to estimate the rotation angle.

[0046] The levitation frequency f d As explained with reference to FIG. 8, the levitation frequency f is determined to be a value common to each phase. However, due to the winding state of the coil 223 and the manufacturing variation of the capacitor 241, the common levitation frequency f d In such a case, the levitation frequency may be determined according to the actual situation of the combination of each electromagnet 220 and capacitor 241. Specifically, the coils 223 and capacitors 241 may be selected so that a common levitation frequency can be used for at least each phase, while allowing the levitation frequency to be different from that of the adjacent phase. In this way, when a different levitation frequency is used for each phase, the amplitude adjustment value A is adjusted so that the contribution of the levitation signal is relatively reduced. C The value of may be reduced.

[0047] The AC motor 100 in the present embodiment described above is a three-phase AC motor, and includes three electromagnets 220 per phase. The control circuit 400 outputs three AC voltage signals V P1 (t)~V P3(t). However, the suspended AC motor according to this embodiment is not limited to a three-phase AC motor, but may be an n-phase AC motor (n is an integer equal to or greater than 3). In this case, the control circuit 400 generates AC voltage signals for n phases. Specifically, in the case of following the first embodiment described above, the ith AC voltage signal (i is an integer from 1 to n) for an n-phase AC motor is expressed by the following formula (9):

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[0048] The configurations of the stator 200 and the rotor 300 in the present embodiment described above, the number and shape of each of the elements constituting them, and the configuration and arrangement of the control circuit 400 may be appropriately changed according to the design specifications and required performance of the AC motor 100. Needless to say, additional elements may be added according to the intended use. For example, a mechanism for preventing the rotor 300 from falling when the AC motor 100 is not driven may be provided. [Explanation of symbols]

[0049] 100...suspended levitation type AC motor, 200...stator, 210...stator base, 220...electromagnet, 221...electromagnet core, 222...bobbin, 222a...fixing hole, 223...coil, 230...adjustment magnet, 241...capacitor, 300...rotor, 310...rotor base, 321...levitation body core, 330...adjustment magnet, 341...inner frame, 342...outer frame, 400...control circuit, 410...modulation synchronization circuit, 421...first AC power source, 422...second AC power source, 423...third AC power source, 510...support, 520...top plate, 530...suspension damper

Claims

1. a stator in which n×m electromagnets (n is an integer of 3 or more, m is an integer of 1 or more) each having a plurality of electromagnet cores are arranged along a circumferential direction in a plane perpendicular to the axis of gravity; a rotor in which a plurality of levitation body cores are radially arranged, the rotor rotating in the air by an attractive force in the gravity axis direction and a rotational force around the gravity axis generated between the plurality of levitation body cores and the plurality of electromagnet cores; A control circuit for generating an n-phase AC voltage signal to be applied to the electromagnet; Equipped with a levitation-type AC motor, wherein the n-phase AC voltage signal is a signal obtained by superimposing, by AM modulation, a levitation signal that is set based on a levitation frequency for maintaining a gap between the rotor and the stator, and a rotation signal that is set based on a rotation frequency corresponding to a target rotation speed of the rotor relative to the stator.

2. 2. The suspended AC motor according to claim 1, wherein the phases of the levitation signals of each phase have a phase difference of 2.pi. / n from each other.

3. 2. The suspended AC motor according to claim 1, wherein the phases of the levitation signals of each phase have no phase difference with each other.

4. 2. The suspended AC motor according to claim 1, wherein the levitation frequencies of the levitation signals of each phase are different from each other.

5. The levitation frequency is determined based on a resonant circuit consisting of a capacitor and the electromagnet, and is expressed as follows: 0 The upper limit frequency f for the value at which the admittance at the resonant frequency is halved is larger than 1 5. The suspended AC motor according to claim 1, wherein the input voltage Vp is set to a value smaller than the input voltage Vp. f 0 =1 / (2π√(LC)) L=μ 0 N 2 S / z 0 (where L is inductance, μ 0 : magnetic permeability of vacuum, N: number of turns of the coil of the electromagnet, S: total effective cross-sectional area of ​​the electromagnet core constituting the electromagnet, z 0 : target gap, C: capacitance of the capacitor)

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