Bearingless motor

Abstract

A bearingless motor and a method of controlling a bearingless motor are described. A bearingless motor includes a rotor having p pole pairs, and a stator assembly including stator windings. The method includes exciting the stator windings to generate a first magnetic field having p pole pairs for generating a torque acting on the rotor. The method comprises exciting the stator winding to generate a second magnetic field comprising a component having q pole pairs for generating a translational force acting on the rotor, where q = p + / -1. Excitating the stator winding to generate the second magnetic field includes applying a modulation factor to the stator winding, the modulation factor including a factor of 2p + / -1.

Description

BACKGROUND

[0001] A bearingless motor is an electric motor having a bearing system integrated within its magnetic circuit, and is capable of rotating a rotor without the need for conventional bearings such as ball bearings. Bearingless motors generally typically have two sets of windings for torque and force generation, provided by independently connected and controlled inverters. SUMMARY

[0002] A first aspect of the application provides a method of controlling a bearingless motor, the bearingless motor comprising a rotor having p pole pairs and a stator assembly comprising stator windings, wherein the method comprises: exciting the stator windings to generate a first magnetic field having p pole pairs for generating a torque acting on the rotor; and exciting the stator windings to generate a second magnetic field comprising a component having q pole pairs for generating a translational force acting on the rotor, wherein q = p ± 1, wherein exciting the stator windings to generate the second magnetic field comprises applying a modulation factor to the stator windings, the modulation factor comprising a factor of 2p ± 1.

[0003] Applying a modulation factor comprising a factor of 2p ± 1 to the stator windings to generate the second magnetic field can result in a shear stress at an outer surface of the rotor which results in a translational force along two orthogonal axes. For example, with a factor of p ± 1, the translational force along one axis, say the x-axis of the rotor, can be zero when viewed in plan, resulting in relatively poor control of the position of the rotor along the x-axis. In contrast, with a factor of 2p ± 1, the translational force can be exerted on the rotor in both the x-axis and y-axis of the rotor when viewed in plan. This can provide improved stability of the rotor position in use.

[0004] Applying the modulation factor to the stator windings can comprise applying the modulation factor to a current induced in the stator windings. The factor can comprise a waveform defined by a cosine having an angular variation defined by 2p ± 1. The factor can comprise a multipole field having a cos(2p + 1) variation around an air gap between the rotor and the stator assembly. Modulation of the current in the stator windings in the positive half cycle of the cosine can be achieved by a factor of 2p + 1. Modulation of the current in the stator windings in the positive half cycle of the cosine can be achieved by a factor of 2p - 1.

[0005] The translational force can comprise a force acting on the rotor along at least two axes within a plane orthogonal to a longitudinal axis of the rotor when viewed in a direction along the longitudinal axis of the rotor.

[0006] The stator windings can comprise a first set of coils and a second set of coils excited in phase with each other. The method can comprise causing the first set of coils and the second set of coils to generate the first magnetic field.

[0007] The method may include exciting a first set of coils and a second set of coils with currents of the same magnitude to generate a first magnetic field.

[0008] The method may include exciting a first set of coils and a second set of coils out of phase with each other to generate a second magnetic field.

[0009] The method may include exciting a first set of coils and a second set of coils with currents of different peak amplitudes to generate a second magnetic field.

[0010] The first and second sets of coils can each form a three-phase winding. The stator windings may include three-phase windings.

[0011] For each phase of the first group of coils, the coils of that phase can be connected in series with each other. For each phase of the second group of coils, the coils of that phase can be connected in series with each other. The coils of corresponding phases between the first and second groups of coils can be connected in parallel with each other.

[0012] Each of the first and second sets of coils can have a base number of 2p±1. The stator windings can include a total of 2 (2p±1) coils.

[0013] The base number of each of the first and second groups of coils can be an integer multiple of 3. The total number of coils in the stator windings can also be an integer multiple of 3.

[0014] The first and second sets of coils can be interleaved, such that every other coil in the stator winding belongs to the same set of coils in the first and second sets.

[0015] This factor can be an integer multiple of 3.

[0016] The second magnetic field may include a first component having q pole pairs and a second component having r pole pairs, where r = 3p ± 1. The method may include exciting the stator windings to generate the second magnetic field, which includes the first component having q pole pairs and the second component having r pole pairs. Alternative modulation factors may include lower r values, such as at r = 2p ± 1, which may be more likely to cause losses in the rotor because harmonic components penetrate deeper into the rotor and cause excessive losses.

[0017] The bearingless motor may include an external rotor motor, and the method may include exciting the stator windings to generate a second magnetic field comprising a component having q = p-1 pole pairs.

[0018] The bearingless motor may include an internal rotor motor, and the method may include exciting the stator windings to generate a second magnetic field including a component having q=p+1 pole pairs.

[0019] The value of p can include integer values. The value of p can be greater than or equal to 6. The value of p can be greater than or equal to 8, greater than or equal to 10, or greater than or equal to 12.

[0020] The method may include controlling a bearingless motor such that the rotor rotates relative to the stator assembly at less than 5,000 rpm, for example less than 4,000 rpm, or less than 3,000 rpm.

[0021] This method may include introducing a negative rotating field relative to the rotor direction to generate a second magnetic field.

[0022] A second aspect of the invention provides a bearingless motor comprising: a rotor assembly including p pole pairs; and a stator assembly including stator windings, wherein the stator windings are configured to: be excited to generate a first magnetic field having p pole pairs for generating torque acting on the rotor; be configured to be excited to generate a second magnetic field including a component having q pole pairs for generating a translational force acting on the rotor, where q = p ± 1; and be configured such that a modulation factor is applied to the stator windings to excite the stator windings to generate the second magnetic field, the modulation factor including a factor 2p ± 1.

[0023] This factor can include a waveform defined by a cosine, which has an angular variation defined by 2p±1. Modulation of the current in the stator winding during the positive half-cycle of the cosine can be achieved through the factor 2p+1. This factor can include a multipole field with a variation of cos(2p+1) around the air gap between the rotor and stator assembly. Modulation of the current in the stator winding during the positive half-cycle of the cosine can be achieved through the factor 2p-1.

[0024] When viewed along the longitudinal axis of the rotor, the translational force can include forces acting on the rotor along at least two axes in a plane orthogonal to the longitudinal axis of the rotor.

[0025] The stator winding may include a first set of coils and a second set of coils, and the first set of coils and the second set of coils may be configured to be excited in phase with each other to generate a first magnetic field.

[0026] The first set of coils and the second set of coils can be configured to be excited by the same amplitude of current to generate the first magnetic field.

[0027] The first and second sets of coils can be configured to be excited out of phase with each other to generate a second magnetic field.

[0028] The first set of coils and the second set of coils can be configured to be excited by currents with different peak amplitudes to generate the second magnetic field.

[0029] The first group of coils and the second group of coils can each form a three-phase winding.

[0030] For each phase of the first group of coils, the coils of that phase can be connected in series with each other. For each phase of the second group of coils, the coils of that phase can be connected in series with each other. The coils of corresponding phases between the first and second groups of coils can be connected in parallel with each other.

[0031] Each of the first and second sets of coils can have a base number of 2p±1. The stator windings can include a total of 2 (2p±1) coils.

[0032] The base number of each of the first and second groups of coils can be an integer multiple of 3. The total number of coils in the stator windings can also be an integer multiple of 3.

[0033] The first and second sets of coils can be interleaved, such that every other coil in the stator winding belongs to the same set of coils in the first and second sets.

[0034] This factor can be an integer multiple of 3.

[0035] The second magnetic field may include a first component having q pole pairs and a second component having r pole pairs, where r = 3p ± 1. The stator windings may be configured to be excited to generate the second magnetic field, which includes the first component having q pole pairs and the second component having r pole pairs. Alternative modulation factors may include lower r values, such as at r = 2p ± 1, which may be more likely to cause losses in the rotor because harmonic components penetrate deeper into the rotor and cause excessive losses.

[0036] Bearingless motors may include external rotor motors, and stator windings may be configured to be excited to generate a second magnetic field comprising a component having q = p-1 pole pairs.

[0037] Bearingless motors may include internal rotor motors, and stator windings may be configured to be excited to generate a second magnetic field comprising a component having q = p + 1 pole pairs.

[0038] The value of p can include integer values. The value of p can be greater than or equal to 6. The value of p can be greater than or equal to 8, greater than or equal to 10, or greater than or equal to 12.

[0039] The stator windings can be configured to be energized such that the rotor rotates relative to the stator assembly at less than 5,000 rpm, for example less than 4,000 rpm, or less than 3,000 rpm.

[0040] The stator windings can be configured to introduce a negative rotating field relative to the rotor direction to generate a second magnetic field.

[0041] The motor can be a slotless motor, for example, in which the stator assembly includes a stator core that does not define any slots for positioning the stator windings.

[0042] The motor can be a slotted motor, for example, in which the stator assembly includes a stator core that defines slots for positioning the stator windings.

[0043] The stator winding may include a double-layer stator winding.

[0044] The stator winding may include a single-layer stator winding.

[0045] The stator winding may include distributed stator windings. For example, each coil of the stator winding includes a first arm located at a first winding position around the periphery of the stator core of the stator assembly, and a second arm located at different second winding positions around the periphery of the stator core assembly. The first winding position may be spaced apart from the second winding position along the periphery of the stator core, with at least one intermediate winding position between the first and second winding positions. Alternatively, the first winding position may be spaced apart from the second winding position along the periphery of the stator core, with exactly one intermediate winding position between the first and second winding positions.

[0046] Stator windings can include toroidal windings, for example, where the first and second arms of each coil of the stator winding are located at the same winding position around the periphery of the stator core. Toroidal windings can result in shorter end windings and lower coil losses.

[0047] Bearingless motors may include control electronics configured to excite stator windings.

[0048] The control electronics may include at least one of a dual-purpose voltage-free inverter, two isolated three-phase inverters, a six-phase inverter, and six independently controllable H-bridges.

[0049] A third aspect of the invention provides an air movement device comprising a bearingless motor according to a second aspect of the invention.

[0050] Air movement devices may include any one of a fan, an airflow heater, an air purifier, and an air humidifier.

[0051] Where appropriate, optional features of one aspect of the invention may be applied in the same way to other aspects of the invention. Attached Figure Description

[0052] Figure 1 An example of a bearingless motor is shown;

[0053] Figure 2 yes Figure 1 An enlarged view of a portion of a bearingless motor;

[0054] Figure 3 An example stator winding configuration is shown;

[0055] Figure 4 It shows the corresponding Figure 3 A table showing example stator winding configurations;

[0056] Figure 5 The diagram illustrates the connection to the control electronics. Figure 2 A schematic diagram of an example stator winding configuration;

[0057] Figure 6 An example stator field harmonic is shown for torque generation;

[0058] Figure 7 An example stator field harmonic is shown for force generation;

[0059] Figure 8 A table illustrating the combination of rotor pole pairs and corresponding modulation factors is shown;

[0060] Figure 9 It shows including Figure 1 Examples of bearingless motor-driven air-moving devices; and

[0061] Figure 10 An example of an alternative stator winding configuration is shown. Detailed Implementation

[0062] exist Figure 1 The image schematically illustrates a bearingless motor 10.

[0063] The bearingless motor 10 includes a rotor 12, a stator assembly 14, and control electronics 16.

[0064] The rotor 12 includes one or more magnets having sixteen magnetic poles 18. Therefore, the rotor 12 has a pole pair number p of eight. The rotor is toroidal.

[0065] The stator assembly 14 includes a stator core 20 and a stator winding 22. The stator core 20 is generally annular in form, and the rotor 12 is located outside the stator core 20. The stator core 20 is a slotless stator core, formed without any teeth.

[0066] exist Figures 1 to 5 The stator winding 22 is schematically shown. The stator winding 22 is formed by thirty coils 24, the number of which is equal to 2 (2p-1), which will be discussed in more detail below. The coils 24 are divided into a first group of coils 26 and a second group of coils 28.

[0067] The first set of coils 26 has a total of fifteen coils 24, which is equal to (2p-1). The first set of coils 26 defines a three-phase winding, wherein a first subset 30 has five coils 24 in phase A, a second subset 32 ​​has five coils 24 in phase B, and a third subset 34 has five coils 24 in phase C. Each coil 24 in the first subset 30 is connected in series with each other. Each coil 24 in the second subset 32 ​​is connected in series with each other. Each coil 24 in the third subset 34 is connected in series with each other.

[0068] The second set of coils 28 has a total of fifteen coils 24, which is equal to (2p-1). The second set of coils 28 defines a three-phase winding, wherein a first subset 36 has five coils 24 in phase A, a second subset 38 has five coils 24 in phase B, and a third subset 40 has five coils 24 in phase C. Each coil 24 in the first subset 36 is connected in series with each other. Each coil 24 in the second subset 38 is connected in series with each other. Each coil 24 in the third subset 40 is connected in series with each other.

[0069] The first subset 30 of the first group of coils 26 is connected in parallel with the first subset 36 of the second group of coils 28 to form a first parallel winding branch 42 for phase A. The second subset 32 ​​of the first group of coils 26 is connected in parallel with the second subset 38 of the second group of coils 28 to form a second parallel winding branch 44 for phase B. The third subset 34 of the first group of coils 26 is connected in parallel with the third subset 40 of the second group of coils 28 to form a third parallel winding branch 46 for phase C.

[0070] The arms of each of the first parallel winding branch 42 for phase A, the second parallel winding branch 44 for phase B, and the third parallel winding branch 46 for phase C (corresponding to the first set of coils 26) are connected to each other in a star configuration at the neutral point N. The arms of each of the first parallel winding branch 42 for phase A, the second parallel winding branch 44 for phase B, and the third parallel winding branch 46 for phase C (corresponding to the second set of coils 26) are each connected to one of the three branches of the suspension inverter 62 of the control electronics 16. The points between the arms of each of the first parallel winding branch 42 for phase A, the second parallel winding branch 44 for phase B, and the third parallel winding branch 46 for phase C are each connected to one of the three branches of the drive inverter 60 of the control electronics 16.

[0071] exist Figure 1 and Figure 2The diagram shows the distribution of the first set of coils 26 and the second set of coils 28 around the periphery of the stator core 20. The coils 24 are arranged in a double layer, such that each coil 24 has a first portion 48 located radially outer relative to the stator core 20 at a position 50 and a second portion 52 located radially inner relative to the stator core at a position 53. Each coil 24 spans two winding positions, such that the first portion 48 is located in the radially outer position 50 of the first winding position 54, and the second portion 52 is located in the radially inner position 53 of the second winding position 56, which is circumferentially spaced from the first winding position 54, with an intermediate winding position 58 in between. Therefore, each coil 24 has a span of two winding positions.

[0072] Each coil 24 in the first group of coils 26 is located in an odd-numbered winding position, while each coil 24 in the second group of coils 28 is located in an even-numbered winding position.

[0073] A general stator winding configuration can be found in Figure 3 and Figure 4 I saw it in [the text]. Figure 3 In the example, each coil spans three winding positions. The input and output connections for phase A are shown for each of the first group of coils 26 and the second group of coils 28. Similar input and output connections are envisioned for phases B and C, where the input connection for phase B of the first group of coils 26 begins at winding position seventeen, and the input connection for phase C of the first group of coils 26 begins at winding position seven. Figure 3 The term “switching function” in this context refers to applying a modulation factor to stator winding 22, as will be discussed in more detail below, and may also be referred to as a reversal state.

[0074] exist Figure 4 The example illustrates the starting coil position, phase, and switching function of coil 24. It should be understood that... Figure 3 The configuration shown can be applied to distributed double-layer windings with any number of spans, or alternatively to single-layer toroidal windings.

[0075] The control electronics 16 includes a drive inverter 60, a suspension inverter 62, and a controller 64. Each of the drive inverter 60 and the suspension inverter 62 is a three-phase inverter. The aforementioned connections of the drive inverter 60 and the suspension inverter 62 with the first set of coils 26 and the second set of coils 28 realize a dual-purpose voltage-free (DPNV) inverter.

[0076] The controller 64 is connected to the drive inverter 60 and the suspension inverter 62, and is configured to control the drive inverter 60 and the suspension inverter 62 to excite the stator winding 22, as will be described in more detail below.

[0077] In use, the bearingless motor 10 is controlled to generate a first magnetic field for generating torque acting on the rotor 12, and to generate a second magnetic field including a component for generating translational force acting on the rotor 12. The following is partly a general discussion applicable to bearingless motors, therefore, reference numerals may be omitted for clarity.

[0078] It has been previously proposed that, in order to generate torque, the number of pole pairs p of the rotor of a bearingless motor and the number of pole pairs of the magnetic field generated by the excitation stator windings must be the same, and the maximum torque per ampere is obtained when the rotor magnetic field angle α and the armature magnetic field angle β are aligned.

[0079] It has been previously proposed that in order to generate a translational force acting on the rotor, the number of pole pairs q of the magnetic field generated by exciting the stator windings must be equal to p ± 1.

[0080] However, it has been found that for a relatively high number of pole pairs p, such as six or more pole pairs, it may be difficult to generate a controllable translational force.

[0081] Specifically, at any point on the surface of the rotor of a bearingless motor, shear stress exists in the circumferential direction. The magnitude of the shear stress is given by the product of the air gap normal (radial) magnetic flux density generated by the rotor magnets and the tangential field strength generated by the axial current in the windings at that angle. This can be expressed by the following equation:

[0082]

[0083] Considering the shear stress on the rotor surface at a specific angle, the shear stress can be composed of two components:

[0084]

[0085]

[0086] The total circumferential force on the rotor is then given by the following equation:

[0087]

[0088] Among them l a It is the axial length of the rotor in the direction orthogonal to the plane of the rotor field, and r is the radius of the rotor.

[0089] therefore:

[0090]

[0091] For all spatial harmonics except those with a single pole pair change (e.g., p±1), the sum of the components will be zero.

[0092] Shear stress can also be expressed as:

[0093]

[0094]

[0095] Therefore, in order to generate translational force, the magnetic field generated by exciting the stator windings must have a harmonic component that is one or one pole less than the rotor pole number p.

[0096] To modify the original p-p pole-pair magnetic field generated by the stator windings to produce torque, a modulation factor m is introduced. The tangential component of H then becomes:

[0097]

[0098]

[0099] To introduce a translational force, m=1 or m=-1.

[0100] For example, consider a rotor with four pole pairs, p=4, then a magnetic field of 3 or 5 pole pairs is required to provide translational force on the rotor.

[0101] By introducing a modulation factor of m=1:

[0102]

[0103]

[0104] Then the shear stress is given by the following equation:

[0105]

[0106]

[0107] Only the two extreme components generate net translational force.

[0108]

[0109] =

[0110] =

[0111] Then Fx becomes zero, as follows:

[0112]

[0113] This means that if the modulation factor is In the y-direction, the force can only be generated. The amplitude can be changed by altering the phase angle of the current or B, but the force in the x-direction cannot be controlled. The fundamental reason is that the bipolar stress field is generated by two counter-rotating bipolar fields, which combine to produce a pulsating field.

[0114] Therefore, the present invention introduces a modulation factor of 2p±1 to generate a magnetic field comprising a component having q pole pairs, for generating a translational force acting on the rotor, where q=p±1, as will now be described.

[0115] for Figure 1 The rotor 12 of the bearingless motor 10 has 8 pole pairs p, then:

[0116]

[0117]

[0118] When m = 2p - 1 = 15, then:

[0119]

[0120]

[0121] The following components correspond to harmonics at q=p-1:

[0122]

[0123] Then the shear stress is given by the following equation:

[0124]

[0125] As mentioned earlier, only the two polar components generate net translational force.

[0126] The translational force in the y-direction is given by the following formula:

[0127]

[0128]

[0129] The translational force in the x-direction is given by the following formula:

[0130]

[0131]

[0132] It can be seen that H can be controlled t The magnitude of the force can be controlled by its size, and the direction of the force can be controlled by controlling its angle relative to the rotor 12.

[0133] In order to keep the force constant in space, it is necessary to make Keep it constant.

[0134] As mentioned above, the following components of the electric and magnetic fields should be considered:

[0135]

[0136] The rotor is at the following angle at any given time:

[0137]

[0138] Where ω r It is the rotational speed of the rotor magnetic field, φ r It is the rotation angle of the rotor magnetic field relative to a fixed point in space.

[0139] The stator H-field that generates the translational force is:

[0140]

[0141] Where ω H It is the rotational speed of the stator magnetic field, φ H It is the rotation angle of the stator magnetic field relative to a fixed point in space with the same rotation angle as the rotor magnetic field.

[0142] Then for Keep constant:

[0143]

[0144] Therefore ω r =-ω H .

[0145] It is also expected that the translational force will rotate together with rotor 12.

[0146] As mentioned above, the following components of the electric and magnetic fields should be considered:

[0147]

[0148] The rotor is at the following angle at any given time:

[0149]

[0150] Where ω r It is the rotational speed of the rotor magnetic field, φ r It is the rotation angle of the rotor magnetic field relative to a fixed point in space.

[0151] The stator H-field that generates the translational force is:

[0152]

[0153] Where ω H It is the rotational speed of the stator magnetic field, φ H It is the rotation angle of the stator magnetic field relative to a fixed point in space with the same rotation angle as the rotor magnetic field.

[0154] Then for Keep constant:

[0155]

[0156] Therefore ω H =-2ω r .

[0157] Considering the above, the control electronics 16 of the bearingless motor 10 can be used to excite the stator windings 22 of the stator assembly 14 to generate a suitable magnetic field to produce torque and translational force to act on the rotor 12.

[0158] In order to generate a first magnetic field for producing torque acting on rotor 12, drive inverter 60 supplies in-phase and same-sized currents to the first set of coils 26 and the second set of coils 28.

[0159] It can be seen that the current flowing from one branch of the drive inverter flows in the same direction through the arm of the first parallel winding branch 42 corresponding to phase A of the first group of coils 26, and in the same direction through the arm of the first parallel winding branch 42 corresponding to phase A of the second group of coils 28. The current flowing from one branch of the drive inverter flows in the same direction through the arm of the second parallel winding branch 44 corresponding to phase B of the first group of coils 26, and in the same direction through the arm of the second parallel winding branch 44 corresponding to phase B of the second group of coils 28. The current flowing from one branch of the drive inverter flows in the same direction through the arm of the third parallel winding branch 46 corresponding to phase C of the first group of coils 26, and in the same direction through the arm of the third parallel winding branch 46 corresponding to phase C of the second group of coils 28.

[0160] To generate a second magnetic field for producing a translational force acting on the rotor, a modulation factor of 2p⁻¹ is applied to the stator winding 22 by reversing the current flowing through the second set of coils 28. In this way, the current is reversed in 2p⁻¹ (i.e., fifteen) coils 24. This is achieved by exciting the stator winding 22 using a suspension inverter 62, while a drive inverter 60 is also used to exciting the stator winding 22. In some examples, the suspension inverter 62 may be used to exciting the stator winding 22 without using the drive inverter 60 to control the translational position of the rotor 22 without generating torque.

[0161] The modulation factor can be considered as a cosine variation around coil 24, where the minimum and maximum values ​​of the cosine are aligned with the coil position, or as a discrete function of length equal to the number of coils, which reverses by a factor of 2p ± 1 around the air gap between rotor 12 and stator assembly 14.

[0162] The current injected by the suspension inverter 62 flows in a first direction through the arms of the first parallel winding branch 42 for phase A, the second parallel winding branch 44 for phase B, and the third parallel winding branch 46 for phase C, corresponding to the second set of coils 28. The current injected by the suspension inverter 62 flows in the opposite second direction through the arms of the first parallel winding branch 42 for phase A, the second parallel winding branch 44 for phase B, and the third parallel winding branch 46 for phase C, corresponding to the first set of coils 26.

[0163] Applying a modulation factor m of 2p⁻¹ in this manner provides a second magnetic field with components having q = p⁻¹ pole pairs, which can interact with rotor 12 to provide a translational force to rotor 12. When viewed in the direction along the longitudinal axis of rotor 12, this translational force can stabilize rotor 12 in a plane orthogonal to the longitudinal axis of rotor 12.

[0164] exist Figure 6 and Figure 7 You can see the uses of each in the middle. Figure 1 Example diagram of the field strength of harmonics in the stator field generated by torque and force in a bearingless motor. Here, the 8p harmonic is shown for... Figure 6 Torque generation is common, while 7p harmonics are... Figure 7 The generation of force in it is universal.

[0165] It should be understood that the force requirement can be determined by monitoring the position of the rotor 12 using an appropriate position sensor, and this information is fed back to the control electronics 16.

[0166] It should be understood that the above can be extended to bearingless motors including any number of pole pairs p.

[0167] Figure 8 Other examples of bearingless motor combinations and the corresponding number of windings are shown in the figure.

[0168] The aforementioned technology can find particular utility in bearingless motors with at least six pole pairs. Given the relatively complex switching requirements, bearingless motors with a relatively high number of pole pairs (such as at least six pole pairs) can also find particular utility in relatively low-speed applications. Figure 1The bearingless motor 10 is designed to be driven at speeds less than 5,000 rpm. Relatively low-speed bearingless motors can be particularly useful in air movement devices such as fans, air purifiers, humidifiers, or airflow heaters.

[0169] Figure 9 An exemplary fan 100 is shown in the figure.

[0170] Although slotless motors have been described above, the techniques discussed in this article can also be applied to slotted motors.

[0171] Similarly, although the above describes double-layer distributed stator windings, the techniques discussed in this paper can also be applied to single-layer toroidal windings. Figure 10 An exemplary toroidal winding scheme 200 is schematically illustrated in the figure.

[0172] While specific examples and embodiments have been described so far, it should be understood that these are merely illustrative and various modifications may be made without departing from the scope of the invention as defined by the claims.

Claims

1. A method for controlling a bearingless motor, the bearingless motor comprising a rotor having p pole pairs and a stator assembly including stator windings, wherein, The method includes: The stator windings are excited to generate a first magnetic field with p pole pairs, for generating torque acting on the rotor; and The stator windings are excited to generate a second magnetic field, the second magnetic field including a component with q pole pairs, for generating a translational force acting on the rotor, where q = p ± 1. Exciting the stator winding to generate the second magnetic field includes applying a modulation factor to the stator winding, the modulation factor including a factor 2p±1.

2. The method according to claim 1, wherein, The stator winding includes a first set of coils and a second set of coils, and the method includes exciting the first set of coils and the second set of coils in phase with each other to generate the first magnetic field.

3. The method according to claim 2, wherein, The method includes exciting the first set of coils and the second set of coils out of phase with each other to generate the second magnetic field.

4. The method according to any one of claims 2 to 3, wherein, The first group of coils and the second group of coils each form a three-phase winding.

5. The method according to claim 4, wherein, For each phase of the first group of coils, the coils of that phase are connected in series with each other; for each phase of the second group of coils, the coils of that phase are connected in series with each other; and the coils of corresponding phases between the first group of coils and the second group of coils are connected in parallel with each other.

6. The method according to any one of claims 2 to 5, wherein, Each of the first group of coils and the second group of coils has a base of 2p±1.

7. The method according to any one of claims 2 to 6, wherein, The first group of coils and the second group of coils are interleaved, such that every other coil of the stator winding belongs to the same group of coils in the first group of coils and the second group of coils.

8. The method according to any one of claims 1 to 7, wherein the second magnetic field comprises a first component having q pole pairs and a second component having r pole pairs, wherein r = 3p ± 1.

9. The method according to any one of claims 1 to 8, wherein p is greater than or equal to 6.

10. A bearingless motor, comprising: Rotor assembly, the rotor assembly comprising p pole pairs; and Stator assembly, which includes stator windings, Wherein, the stator winding: It is configured to be excited to generate a first magnetic field with p pole pairs, which is used to generate torque acting on the rotor; The rotor is configured to be excited to generate a second magnetic field, the second magnetic field including a component having q pole pairs, for generating a translational force acting on the rotor, where q = p ± 1; and The configuration is such that a modulation factor is applied to the stator winding to excite the stator winding to generate the second magnetic field, the modulation factor including a factor of 2p±1.

11. The bearingless motor according to claim 10, wherein, The stator winding includes a first set of coils and a second set of coils, and the first set of coils and the second set of coils are configured to be excited in phase with each other to generate the first magnetic field.

12. The bearingless motor according to any one of claims 10 to 11, wherein, The first group of coils and the second group of coils each form a three-phase winding.

13. The bearingless motor according to claim 12, wherein, For each phase of the first group of coils, the coils of that phase are connected in series with each other; for each phase of the second group of coils, the coils of that phase are connected in series with each other; and the coils of corresponding phases between the first group of coils and the second group of coils are connected in parallel with each other.

14. The bearingless motor according to any one of claims 10 to 13, wherein, Each of the first group of coils and the second group of coils has a base of 2p±1.

15. The bearingless motor according to any one of claims 10 to 14, wherein, The first group of coils and the second group of coils are interleaved, such that every other coil of the stator winding belongs to the same group of coils in the first group of coils and the second group of coils.

16. The bearingless motor according to any one of claims 10 to 15, wherein, The second magnetic field includes a first component with q pole pairs and a second component with r pole pairs, where r = 3p ± 1.

17. The bearingless motor according to any one of claims 10 to 16, wherein, p is greater than or equal to 6.

18. The bearingless motor according to any one of claims 10 to 17, wherein, The motor is a slotless motor.

19. The bearingless motor according to any one of claims 10 to 18, wherein, The stator windings include distributed stator windings.

20. An air-moving device comprising a bearingless motor according to any one of claims 10 to 19.

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