Asymmetric radial electromagnetic bearing and design method thereof

Abstract

The invention discloses an asymmetric radial electromagnetic bearing and a design method thereof, and the asymmetric radial electromagnetic bearing comprises an asymmetric radial electromagnetic bearing stator, an asymmetric radial electromagnetic bearing rotor and a winding coil. The design method of the asymmetric radial electromagnetic bearing comprises the following steps: pre-determining parameters; calculating the electromagnetic force of the asymmetric radial electromagnetic bearing in the X and Y directions; and calculating each structural parameter of the asymmetric radial electromagnetic bearing. Compared with a traditional symmetric radial electromagnetic bearing structure and an asymmetric electromagnetic bearing disclosed at present, the asymmetric radial electromagnetic bearing has the advantages that electromagnetic force coupling in the horizontal and vertical directions is small, control is facilitated, electromagnetic loss is low, and temperature rise of the rotor can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic bearings, and in particular to a low-power radial electromagnetic bearing and a design method thereof. Background Art

[0002] Magnetic bearings have the advantages of no contact, no wear, no lubrication, high speed, long life, and controllability, and are widely used in flywheel energy storage systems, medical equipment, turbine machinery, and mechanical manufacturing tools. However, whether these advantages can be achieved depends to a certain extent on the rationality of the structure and design of the electromagnetic bearings.

[0003] In existing magnetic levitation technology solutions, horizontal rotating machinery is mostly supported by radial electromagnetic bearings with symmetrical structures. At this time, the radial electromagnetic bearings need to offset the gravity of the rotor system during operation. Based on differential control theory, the controller of the radial electromagnetic bearing will always generate a large control current to offset gravity, which will cause the electromagnetic bearing to generate large electromagnetic losses during operation. If the rotor runs in a vacuum, the temperature rise of the electromagnetic bearing caused by the loss will affect the performance of the equipment and even cause safety accidents.

[0004] In addition, the prior art CN115111265A discloses an asymmetric electromagnetic bearing, including a rotor and a stator provided with a plurality of magnetic poles. The cross-sectional areas S of the magnetic poles located in the first and second quadrants are the same, and the cross-sectional areas s of the magnetic poles located in the third and fourth quadrants are the same, and S>s. And the number of turns of the coils wound around each group of magnetic poles is the same. The prior art CN115095602A discloses an asymmetric electromagnetic bearing, including a rotor and a stator provided with a plurality of magnetic poles. The cross-sectional areas of the magnetic poles located in the first, second, third and fourth quadrants are the same, but the number of turns of the coils located in the first and second quadrants are both N, and the number of turns of the coils located in the third and fourth quadrants are both M, and N>M.

[0005] In the technical solutions of the above two inventions, the magnetic pole structures are relatively complex, and the actual electromagnetic force generated in any quadrant will affect the electromagnetic force in the horizontal and vertical directions, which is not conducive to control. Summary of the invention

[0006] The invention provides an asymmetric radial electromagnetic bearing and a design method thereof.

[0007] The asymmetric radial electromagnetic bearing in the present invention specifically includes: an asymmetric radial electromagnetic bearing rotor, an asymmetric radial electromagnetic bearing stator, and a winding coil. Among them, the asymmetric radial electromagnetic bearing rotor and the asymmetric radial electromagnetic bearing stator are both made of stacked silicon steel sheets, and the magnetic poles of the asymmetric radial electromagnetic bearing stator are divided into four groups, namely, the upper magnetic pole pair, the right magnetic pole pair, the lower magnetic pole pair and the left magnetic pole pair. And the upper magnetic pole pair magnetic pole column area > the right magnetic pole pair magnetic pole column area = the left magnetic pole pair magnetic pole column area > the lower magnetic pole pair magnetic pole column area, and the magnetic pole column area ratio is given during calculation. The winding coil is wound by enameled wire, the number of turns of the upper winding coil > the number of turns of the right winding coil = the number of turns of the left winding coil > the number of turns of the lower winding coil, and the specific number of turns is determined by the formula calculation in the design method. The winding coil is wound by enameled wire.

[0008] The design method of the present invention specifically comprises the following steps:

[0009] Step (1): predetermine parameters;

[0010] Specifically, it includes determining the material of the electromagnetic bearing and the maximum magnetic induction intensity B max ; Determine the number of magnetic poles N P 8. Calculate the actual maximum load F required for each magnetic pole pair based on the rotor mass M and the maximum dynamic unbalance force F of the horizontal rotating machinery. imax ; Determine the inner diameter d1 of the asymmetric radial electromagnetic bearing rotor according to the outer diameter of the rotor of the horizontal rotating machinery; the air gap size s0; the maximum coil current I max And the maximum current density J and the slot fill rate λ.

[0011] Step (2): Calculate the electromagnetic force of the asymmetric radial electromagnetic bearing in the X and Y directions. The specific solution process is as follows:

[0012] According to the virtual displacement principle, the electromagnetic force of each pair of magnetic poles on the rotor can be obtained:

[0013]

[0014] Among them, α is half of the angle between the two magnetic poles of the electromagnetic bearing.

[0015] In the differential drive mode, the electromagnetic force generated by the right magnetic pole on the rotor is

[0016]

[0017] The magnitude of the electromagnetic force exerted by the left magnetic pole on the rotor is

[0018]

[0019] Its electromagnetic force in the X direction can be expressed as

[0020] f x =f x+ -f x- (4)

[0021] Similarly, the electromagnetic force generated by the upper magnetic pole on the rotor is

[0022]

[0023] The magnitude of the electromagnetic force exerted by the lower magnetic pole on the rotor is

[0024]

[0025] Its electromagnetic force in the Y direction can be expressed as

[0026] f y =f y+ -f y- (7)

[0027] Step (3): Calculate the various structural parameters of the asymmetric radial electromagnetic bearing. The specific solution process is as follows:

[0028] Stator pole width:

[0029]

[0030] t1:t2:t3:t4=6:5:4:5 (9)

[0031] The stator yoke width and the rotor core width should not be less than the stator pole width, generally C = (1 ~ 1.5) t i , in the present invention, the stator yoke width is taken as:

[0032] C=t1 (10)

[0033] Rotor core width:

[0034] c=t1 (11)

[0035] Rotor outer diameter:

[0036] d2=d1+2c (12)

[0037] Stator inner diameter:

[0038] D1=d2+2s0 (13)

[0039] Air gap cross-sectional area:

[0040] A i =t i l (14)

[0041] Where l is the axial width of the stator. From formula (1) and formula (14), taking i = 1, the axial length of the stator can be obtained.

[0042]

[0043] Rotor axial length:

[0044] L=l+5 (16)

[0045] By substituting the actual maximum load capacity and maximum current value into formula (1), the number of winding coil turns of each magnetic pole pair can be obtained:

[0046]

[0047] Minimum bare wire diameter:

[0048]

[0049] Furthermore, the diameter d of the enameled wire is determined according to the minimum bare wire diameter.

[0050] According to the number of turns and structure of the winding coil, the coil slot area can be obtained as:

[0051]

[0052] In order to reserve enough space to install the winding coil, the radial height of the magnetic pole is:

[0053] H=(1~1.4)H' (20)

[0054] Winding coil slot bottom diameter:

[0055] D2=D1+2H (21)

[0056] Stator outer diameter:

[0057] D3=D2+2C (22)

[0058] Beneficial effects:

[0059] Compared with the traditional symmetrical radial electromagnetic bearing structure and the currently disclosed asymmetric electromagnetic bearing, on the one hand, the coupling of the electromagnetic force in the horizontal and vertical directions is small, which is conducive to control; on the other hand, its electromagnetic loss is low, which can reduce the temperature rise of the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A schematic diagram showing the structure of an asymmetric radial electromagnetic bearing;

[0061] Figure 2 An equivalent magnetic circuit diagram showing an asymmetric radial electromagnetic bearing;

[0062] Figure 3 A schematic diagram showing the structural parameters of an asymmetric radial electromagnetic bearing;

[0063] Figure 4 A magnetic flux density distribution diagram showing an asymmetric radial electromagnetic bearing in working condition;

[0064] Figure 5 Characteristic curves showing the electromagnetic force (Y direction) of the asymmetric radial electromagnetic bearing with control current under different rotor displacements;

[0065] Figure 6 A comparison chart showing the total power loss of an asymmetric radial electromagnetic bearing and a traditional symmetrical radial electromagnetic bearing when supporting the rotor of the same horizontal machine. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the protection scope of the present invention.

[0067] like Figure 1 As shown, the asymmetric radial electromagnetic bearing in the present invention includes: an asymmetric radial electromagnetic bearing rotor 1, an asymmetric radial electromagnetic bearing stator 2, and a winding coil 3. Among them, the asymmetric radial electromagnetic bearing rotor 1 and the asymmetric radial electromagnetic bearing stator 2 are both made of stacked silicon steel sheets, and the magnetic poles of the asymmetric radial electromagnetic bearing stator 2 are divided into four groups, namely, the upper magnetic pole pair, the right magnetic pole pair, the lower magnetic pole pair and the left magnetic pole pair. And the upper magnetic pole pair magnetic pole column area > the right magnetic pole pair magnetic pole column area = the left magnetic pole pair magnetic pole column area > the lower magnetic pole pair magnetic pole column area, and the magnetic pole column area ratio is given during calculation. The winding coil 3 is wound by enameled wire, the number of turns of the upper winding coil > the number of turns of the right winding coil = the number of turns of the left winding coil > the number of turns of the lower winding coil, and the specific number of turns is determined by the formula calculation in the design method.

[0068] The asymmetric radial electromagnetic bearing of the present invention comprises an asymmetric radial electromagnetic bearing rotor, an asymmetric radial electromagnetic bearing stator and a winding coil. The following is a detailed description of its features:

[0069] Asymmetric radial electromagnetic bearing rotor and stator: The rotor and stator of the asymmetric radial electromagnetic bearing are made of laminated silicon steel sheets. Silicon steel sheets have excellent magnetic conductivity and low hysteresis loss, which is crucial to the performance of electromagnetic bearings. The design of the rotor and stator adopts an asymmetric structure, which helps to reduce the electromagnetic force coupling of the electromagnetic bearing in the horizontal and vertical directions, thereby improving the stability and accuracy of the control.

[0070] Stator pole design: The stator poles are divided into four groups, namely the upper pole pair, the right pole pair, the lower pole pair and the left pole pair. This grouping design not only helps to achieve asymmetric electromagnetic force distribution, but also optimizes the load-bearing capacity and control performance of the electromagnetic bearing. The pole column areas of these four groups of pole pairs are not equal, but are arranged in the order of upper pole pair pole column area > right pole pair pole column area = left pole pair pole column area > lower pole pair pole column area, and have a given pole column area ratio. The setting of this area ratio is based on the precise calculation and optimization of the electromagnetic force, aiming to further reduce electromagnetic losses and improve efficiency.

[0071] Design of winding coil: The winding coil is made of enameled wire, which is a key component for generating electromagnetic force in electromagnetic bearings. In response to the magnetic pole design of the stator, the number of turns of the winding coil is also asymmetric, specifically, the number of turns of the upper winding coil> the number of turns of the right winding coil= the number of turns of the left winding coil> the number of turns of the lower winding coil. This distribution of turns combined with the area ratio of the magnetic pole column enables the electromagnetic bearing to generate a more balanced and easy-to-control electromagnetic force in the horizontal and vertical directions. At the same time, this design also helps to reduce electromagnetic losses and temperature rise of the rotor, thereby improving the reliability and life of the electromagnetic bearing. In addition, the number of turns and material selection of the winding coil are also based on precise calculation and optimization to ensure that the electromagnetic loss and temperature rise are minimized as much as possible while meeting the load-bearing capacity. The use of enameled wire ensures the insulation performance and stability of the winding coil.

[0072] The design method of the present invention is as follows: The design method includes three main steps, namely, predetermining parameters, calculating the electromagnetic forces of the asymmetric radial electromagnetic bearing in the X and Y directions, and calculating the structural parameters of the asymmetric radial electromagnetic bearing. The following is a detailed description of these three steps.

[0073] Step (1): Determine parameters in advance.

[0074] Before designing an asymmetric radial electromagnetic bearing, a series of key parameters need to be determined in advance. These parameters will directly affect the performance and structural design of the electromagnetic bearing. Specific parameters include: Material of the electromagnetic bearing: Selecting the right material is crucial to the performance of the electromagnetic bearing. Usually, the stator and rotor are made of laminated silicon steel sheets to reduce eddy current loss and hysteresis loss. Maximum magnetic induction intensity B max :This is an important parameter in the design of electromagnetic bearings, which determines the load-bearing capacity and electromagnetic loss of the electromagnetic bearings. p :The number of magnetic poles needs to be determined according to actual needs and application scenarios. In this method, the number of magnetic poles N P Determined to be 8. Rotor mass M and maximum dynamic unbalance force F max :These parameters are used to calculate the actual maximum load F required for each pole pairimax , ensuring that the electromagnetic bearing can stably support the rotor. Rotor outer diameter: used to determine the inner diameter d1 of the asymmetric radial electromagnetic bearing rotor. Air gap size s0: The air gap is the gap between the stator and the rotor in the electromagnetic bearing, and its size directly affects the electromagnetic force and electromagnetic loss. Coil maximum current I max and maximum current density J: These parameters are used to design the winding coil to ensure that the coil does not exceed its load limit during operation. Slot fill rate λ: The slot fill rate refers to the filling degree of the winding coil in the slot, which affects the heat dissipation and electrical performance of the electromagnetic bearing. When determining these parameters, it is necessary to comprehensively consider factors such as the application scenario, performance requirements, and cost of the electromagnetic bearing to ensure the rationality and feasibility of the design.

[0075] Step (2): Calculate the electromagnetic forces of the asymmetric radial electromagnetic bearing in the X and Y directions.

[0076] After determining the key parameters, the next step is to calculate the electromagnetic force of the asymmetric radial electromagnetic bearing in the X and Y directions. This step is a key link in the design process, because the magnitude and direction of the electromagnetic force directly affect the load-bearing capacity and control performance of the electromagnetic bearing. According to the principle of virtual displacement, the electromagnetic force formula of each pair of magnetic poles on the rotor can be derived. In the differential drive mode, the electromagnetic force of the right magnetic pole pair and the left magnetic pole pair in the X direction, as well as the electromagnetic force of the upper magnetic pole pair and the lower magnetic pole pair in the Y direction can be calculated respectively. Then, by synthesizing these electromagnetic forces, the electromagnetic resultant force of the asymmetric radial electromagnetic bearing in the X and Y directions can be obtained. The calculation results of this step will provide an important basis for the subsequent structural parameter design, ensuring that the electromagnetic bearing can meet the requirements of load-bearing capacity and control performance.

[0077] Step (3): Calculate the structural parameters of the asymmetric radial electromagnetic bearing.

[0078] After determining the electromagnetic force, the next step is to calculate the various structural parameters of the asymmetric radial electromagnetic bearing. These parameters include stator pole width, stator yoke width, rotor core width, rotor outer diameter, stator inner diameter, air gap cross-sectional area, stator axial length, rotor axial length, winding coil turns, minimum bare wire diameter, enameled wire diameter, coil slot area, pole radial height, and winding coil slot bottom diameter.

[0079] The calculation of these structural parameters needs to be based on the calculation results of electromagnetic force and the working principle of electromagnetic bearings. Through the derivation and calculation of a series of formulas, the specific values ​​of these structural parameters can be obtained. These parameters will directly guide the processing and assembly process of electromagnetic bearings to ensure that electromagnetic bearings can work stably according to design requirements.

[0080] When calculating structural parameters, special attention should be paid to the mutual influence and restriction relationship between the parameters to ensure the rationality and feasibility of the calculation results. At the same time, the actual conditions of processing and assembly should be considered to make appropriate corrections and adjustments to the calculation results.

[0081] This example uses a real rotor structure of a horizontal machine, whose total rotor mass is 20kg, maximum unbalanced force is 263.19N, and rotor outer diameter is 36mm. Next, the design method of the present invention is described in detail.

[0082] In actual design, a 3-fold margin is taken, and the bearing capacity of the asymmetric radial electromagnetic bearing used to offset the dynamic unbalanced force of the rotor is 789.57 N. Since the rotor is a horizontal structure, the asymmetric radial electromagnetic bearing also needs to provide a static bearing capacity (used to offset gravity) of 200 N. Therefore, the maximum electromagnetic bearing capacity F that a single radial electromagnetic bearing needs to provide to the rotor in the four directions of up, right, down, and left is 1max 、F 2max、 F 3max、 F 4max They are 494.79N, 394.79N, 294.79N and 394.79N respectively. In addition, according to the actual properties of the material, take B max =1.2T, according to the rotor outer diameter, d1 = 36mm. Take the air gap value s0 = 0.5mm, the maximum coil current I max The maximum current density J is 3.5A / mm 2 , the slot filling rate λ is 0.7.

[0083] Figure 2 The equivalent magnetic circuit diagram of the asymmetric radial electromagnetic bearing and the definitions of the X and Y directions are given, and combined with Figure 2 The electromagnetic force expressions of the asymmetric radial electromagnetic bearing in the X and Y directions can be derived from formulas (1)-(7).

[0084] Figure 3 The structural parameters that need to be solved for the asymmetric radial electromagnetic bearing are marked. By combining the design formulas (8), (9), (11), (12), and (13), t1, t2, t3, t4, D1, and d2 can be calculated. C can be calculated from formula (10). Combining formula (1) with formula (14), and removing i=1, l can be obtained. L can be calculated from formula (16). By substituting the actual maximum load-bearing capacity and maximum current values ​​of the upper, right, lower, and left sides into formula (1), the winding coil turn values ​​of the four magnetic pole pairs on the upper, right, lower, and left sides can be obtained as N1, N2, N3, and N4, respectively. d can be calculated from formula (18) w , and according to d wThe value of d can be determined. By using formulas (19), (20), and (21) and taking i = 1, H and D2 can be obtained. D3 can be obtained by using formula (22). After the solution is completed, the specific numerical results of each parameter are shown in the table below.

[0085] Asymmetric radial electromagnetic bearing structure design parameter table

[0086]

[0087] Furthermore, the above parameters are used to establish a simulation model of an asymmetric radial electromagnetic bearing.

[0088] Figure 4 It is the magnetic flux distribution of an asymmetric radial electromagnetic bearing in working condition. The magnetic flux distribution is uniform and there is no coupling between the magnetic pole pairs.

[0089] Figure 5 It is the characteristic curve of electromagnetic force (Y direction) of asymmetric radial electromagnetic bearing with control current under different rotor displacements. Obviously, under different rotor displacements, asymmetric radial electromagnetic bearings can reach half of the rotor gravity (F = 100N) under a certain control current. Therefore, asymmetric radial electromagnetic bearings have the bearing capacity to suspend the rotor at any position or return the rotor from the eccentric position to the central working point.

[0090] Figure 6 A comparison of the total power loss of an asymmetric radial electromagnetic bearing and a conventional symmetrical radial electromagnetic bearing when supporting the rotor of the same horizontal machine is shown. Compared with a symmetrical structure, the asymmetric radial electromagnetic bearing of the present invention has lower electromagnetic loss.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An asymmetric radial electromagnetic bearing, characterized in that : It includes an asymmetric radial electromagnetic bearing rotor, an asymmetric radial electromagnetic bearing stator, and a winding coil; wherein the asymmetric radial electromagnetic bearing rotor and the asymmetric radial electromagnetic bearing stator are both formed by stacking silicon steel sheets, and the magnetic poles of the asymmetric radial electromagnetic bearing stator are divided into four groups, namely an upper magnetic pole pair, a right magnetic pole pair, a lower magnetic pole pair, and a left magnetic pole pair, and the magnetic pole column area of ​​the upper magnetic pole pair>the magnetic pole column area of ​​the right magnetic pole pair=the magnetic pole column area of ​​the left magnetic pole pair>the magnetic pole column area of ​​the lower magnetic pole pair, and has a given magnetic pole column area ratio; the winding coil is wound by enameled wire, and the number of turns of the upper winding coil>the number of turns of the right winding coil=the number of turns of the left winding coil>the number of turns of the lower winding coil.

2. A method for designing an asymmetric radial electromagnetic bearing, used for designing an asymmetric radial electromagnetic bearing according to claim 1, characterized in that: The design method comprises the steps of (1): predetermining parameters; Step (2): Calculating the electromagnetic forces of the asymmetric radial electromagnetic bearing in the X and Y directions; Step (3): Calculate the structural parameters of the asymmetric radial electromagnetic bearing.

3. The design method of an asymmetric radial electromagnetic bearing according to claim 2, characterized in that: Step (1) specifically includes determining the material of the electromagnetic bearing and the maximum magnetic induction intensity B max ; Determine the number of magnetic poles N p =8; Based on the rotor mass M and the maximum dynamic unbalance force F of the horizontal rotating machinery max Calculate the actual maximum load F required for each pole pair imax ; Determine the inner diameter d1 of the asymmetric radial electromagnetic bearing rotor according to the outer diameter of the rotor of the horizontal rotating machinery; the air gap size s0; the maximum coil current I max And the maximum current density J and the slot fill rate λ.

4. The design method of an asymmetric radial electromagnetic bearing according to claim 3, characterized in that: The specific solution process of step (2) is as follows: According to the virtual displacement principle, the electromagnetic force of each pair of magnetic poles on the rotor can be obtained: Among them, α is half of the angle between the two magnetic poles of the electromagnetic bearing; In differential drive mode, the electromagnetic force generated by the right magnetic pole on the rotor is: The magnitude of the electromagnetic force generated by the left magnetic pole on the rotor is: Its electromagnetic force in the X direction can be expressed as: f x =f x+ -f x- ; (4) Similarly, the magnitude of the electromagnetic force generated by the upper magnetic pole on the rotor is: The magnitude of the electromagnetic force generated by the lower magnetic pole on the rotor is: Its electromagnetic force in the Y direction can be expressed as: f y =f y+ -f y- 。 (7) 5. The design method of an asymmetric radial electromagnetic bearing according to claim 4, characterized in that: The specific solution process of step (3) is as follows: Stator pole width: t1:t2:t3:t4=6:5:4:5; (9) Take the stator yoke width: C=t1; (10) Rotor core width: c=t1; (11) Rotor outer diameter: d2=d1+2c; (12) Stator inner diameter: D1=d2+2s0; (13) Air gap cross-sectional area: A i =t i l; (14) Where l is the axial width of the stator. According to formula (1) and formula (14), taking i = 1, the axial length of the stator can be obtained as: Rotor axial length: L＝l+5； (16) By substituting the actual maximum load capacity and maximum current value into formula (1), the number of winding coil turns of each magnetic pole pair can be obtained: Minimum bare wire diameter: Then, the diameter d of the enameled wire is determined according to the minimum bare wire diameter; According to the number of turns and structure of the winding coil, the coil slot area can be obtained as: Magnetic pole radial height: H=(1~1.4)H'; (20) Winding coil slot bottom diameter: D2=D1+2H; (21) Stator outer diameter: D3=D2+2C. (22).

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