A flexible PCB hexagonal slot winding

Abstract

A flexible PCB hexagonal slotted winding comprises a flexible PCB winding and slots. The flexible PCB winding uses a double-layer flexible PCB as a substrate, and the flexible PCB winding uses copper foil as a conductor. Vias are used on both sides of the substrate for electrical connection. The copper foil is printed on the flexible PCB. The flexible PCB winding is wired in a hexagonal stacked winding distribution method, with the six sides of the hexagonal winding being sequentially designated as sections I, II, III, IV, V, and VI, with sections II and V being of equal length, and sections III and IV being of equal length. The slots have a rectangular cross-section and are symmetrically distributed about the vertical center lines of the copper foils. The medium inside the slots is air. The slots are located on the copper foils of the flexible PCB winding and are formed by cutting and subtracting material on the copper foils. The flexible PCB winding is applied to a radial flux slotless permanent magnet motor, and the flexible PCB winding adopts an A, B, and C three-phase star-connected power supply method. The winding eddy current loss of the flexible PCB hexagonal slotted winding is (1-sinβ) when the slots are not cut. 2 times, where β is the wiring tilt angle of the hexagonal winding.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor windings, and in particular relates to a flexible PCB hexagonal slotted winding. Background Art

[0002] Applying flexible PCB technology to motor winding production has enabled the development of high-performance radial flux slotless permanent magnet motors. In some specialized applications, flexible PCB windings have replaced traditional wire-wound windings. Because the current-carrying conductors are printed on the flexible PCB, there's no need for the braiding required for wire-wound windings. Printed flexible PCB windings can be shaped as desired, solving winding topologies difficult to achieve with traditional wired technology. Furthermore, flexible PCB windings offer variable conductor track widths and a better copper fill factor, optimizing the performance of radial flux slotless permanent magnet motors.

[0003] Flexible PCB windings, due to their precision, are often used in high-speed small motors. However, eddy current losses are a significant issue for high-speed motors, impacting motor performance. While flexible PCB windings can improve motor performance, they also have certain drawbacks. For example, compared to traditional wire-wound windings, flexible PCB windings have a larger width-to-thickness ratio for windings of the same cross-sectional area, exposing a larger area of ​​the winding to the radially varying magnetic field, making them more susceptible to eddy current losses.

[0004] Currently, the traditional solution to address eddy current losses is to reduce the copper foil width of the windings, increase the number of turns, and connect the windings in series or parallel. However, series connection generates very high induced voltages, while parallel connection can cause circulating currents in the conductors. Therefore, traditional solutions to reduce eddy current effects in flexible PCB windings are relatively complex. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a flexible PCB hexagonal slotted winding. This solves the eddy current problem by adding slots to each copper foil of the flexible PCB winding. This is equivalent to improving the flexible PCB winding without affecting the motor supply voltage. The addition of the slots reduces the winding area exposed to the radial magnetic field without changing the number of turns of the winding. This reduces the winding area generating eddy current effects without affecting the winding back electromotive force. Compared with traditional solutions, this eliminates the back electromotive force adjustment process, making operation more convenient, and also weakening the winding eddy current effect.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a flexible PCB hexagonal slotted winding, comprising a flexible PCB winding and a slot, wherein the flexible PCB winding adopts a double-layer flexible PCB as a substrate, and the flexible PCB winding adopts copper foil as a conductor; vias are used on both sides of the substrate for electrical connection; the copper foil is printed on the flexible PCB; the winding wiring method of the flexible PCB winding adopts a hexagonal stacked winding distribution method, and the six sides of the hexagonal winding are sequentially recorded as section I, section II, section III, section IV, section V and section VI, and section II and section V are of equal length, and section III and section IV are of equal length; the cross-section of the slot is rectangular, and the slots are symmetrically distributed about the vertical center lines of each copper foil; the medium inside the slot is air; the slot is located on each copper foil of the flexible PCB winding, and the slot is formed on the copper foil by cutting subtractively.

[0007] The flexible PCB winding is applied to a radial flux slotless permanent magnet motor, and the flexible PCB winding adopts an A, B, and C three-phase star-connected power supply mode.

[0008] The size of the groove is different for different flexible PCB windings; the length of the groove is equal to the length of section II of the hexagonal winding; the width of the groove is equal to the difference between the lengths of sections II and III of the hexagonal winding; the depth of the groove is equal to the thickness of the copper foil; when the wiring inclination angle of the hexagonal winding is β, the width of the groove is y and satisfies the formula y=b(1-sinβ), and 0°<β<90°, where b is the width of section II of the hexagonal winding.

[0009] When the width of section II of the hexagonal winding is selected, the formula b=I / (t×J) is satisfied, where b is the width of section II of the hexagonal winding, I is the required winding current of the motor, J is the required winding density of the motor, and t is the thickness of the copper foil; when the width of section III of the hexagonal winding is selected, the formula c=b×sinβ is satisfied, where c is the width of section III of the hexagonal winding, b is the width of section II of the hexagonal winding, and β is the wiring inclination angle of the hexagonal winding.

[0010] When selecting the wiring inclination angle of the hexagonal winding, β=45° is preferably selected.

[0011] The eddy current loss of the flexible PCB hexagonal slotted winding is (1-sinβ) when the slots are not cut. 2 times, where β is the wiring tilt angle of the hexagonal winding.

[0012] Beneficial effects of the present invention:

[0013] When the flexible PCB hexagonal slotted winding of the present invention is applied to a radial flux slotless permanent magnet motor, it can eliminate the cogging torque caused by stator slots, just as with conventional radial flux slotless permanent magnet motors using wire-wound windings. However, the flexible PCB hexagonal slotted winding of the present invention offers greater advantages in manufacturing and performance optimization. Conventional wire-wound windings require complex machining during manufacturing, making winding formation difficult. They require polyester material to secure them to the stator yoke, resulting in limited and relatively fixed winding wiring options, making them difficult to install on the production line for micro motors. In contrast, the flexible PCB hexagonal slotted winding of the present invention is printed on a flexible substrate using etching technology and photo-imaging patterns. The winding can be formed into any desired shape based on specific needs, facilitating subsequent winding optimization. The printed flexible PCB hexagonal slotted winding is simply rolled, positioned, and glued to the motor stator yoke for immediate use, making wiring installation easy for micro motors.

[0014] Traditional flexible PCB windings generate eddy currents due to the excessive area of ​​the winding exposed to the radial time-varying magnetic field. Conventional methods for mitigating these eddy currents reduce the width of the winding copper foil, thereby reducing the area exposed to the radial time-varying magnetic field. However, to maintain the copper fill factor, the number of copper foils in the windings must be increased, which undoubtedly affects the motor's back EMF. The present invention, in contrast, addresses the eddy current problem by adding grooves to each copper foil in the flexible PCB winding. This improves the flexible PCB winding without affecting the motor's supply voltage. The addition of the grooves reduces the area of ​​the winding exposed to the radial magnetic field without changing the number of turns. This reduces the area of ​​the winding that generates eddy currents without affecting the winding's back EMF. Compared to traditional solutions, this eliminates the need to adjust the back EMF, making operation more convenient and simultaneously reducing the eddy current effect in the winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a planar schematic diagram of a double-layer flexible PCB winding using a two-pole radial flux slotless permanent magnet motor as an example;

[0016] Figure 2 This is a top-level plan view of a double-layer flexible PCB winding using a two-pole radial flux slotless permanent magnet motor as an example;

[0017] Figure 3 This is a bottom-level plan view of a double-layer flexible PCB winding using a two-pole radial flux slotless permanent magnet motor as an example;

[0018] Figure 4 This is a simplified schematic diagram of the hexagonal winding of a double-layer flexible PCB without slots;

[0019] Figure 5 This is a simplified partial enlarged schematic diagram of the hexagonal winding of a double-layer flexible PCB without slots;

[0020] Figure 6 It is a schematic diagram of the structure of the flexible PCB hexagonal winding;

[0021] Figure 7 This is a simplified schematic diagram of the hexagonal winding of a double-layer flexible PCB when slotting;

[0022] Figure 8 This is a simplified partial enlarged schematic diagram of the hexagonal winding of a double-layer flexible PCB during slotting;

[0023] In the figure, 1 is the flexible PCB winding, 2 is the slot, 11 is the copper foil, 12 is the via, 13 is the substrate, x is the length of the slot, y is the width of the slot, β is the wiring inclination angle of the hexagonal winding, b is the width of the second section of the hexagonal winding, and c is the width of the third section of the hexagonal winding. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] A flexible PCB hexagonal slotted winding comprises a flexible PCB winding 1 and slots 2. The flexible PCB winding 1 uses a double-layer flexible PCB as a substrate 13, and copper foil 11 as a conductor. Vias 12 are used on both sides of the substrate 13 for electrical connection. The copper foil 11 is printed on the flexible PCB. The flexible PCB winding 1 is arranged in a hexagonal stacked winding pattern, with the six sides of the hexagonal winding being sequentially designated as sections I, II, III, IV, V, and VI, with sections II and V being of equal length, and sections III and IV being of equal length. The slots 2 have a rectangular cross-section and are symmetrically distributed about the vertical centerlines of the copper foils 11. The medium within the slots 2 is air. The slots 2 are located on the copper foils 11 of the flexible PCB winding 1 and are formed by cutting the copper foils 11.

[0026] Specifically, during production, the winding wiring method must be designed first, and then the copper foil 11 is wired according to the designed wiring method to make a double-layer flexible PCB winding 1 on the double-layer flexible PCB. Taking the double-layer flexible PCB winding of a two-pole slotless permanent magnet motor as an example, Figures 1 to 3 As shown, the solid line represents the top layer wiring of the double-layer flexible PCB winding 1, and the dashed line represents the bottom layer wiring of the double-layer flexible PCB winding 1. Like conventional double-layer windings, the double-layer flexible PCB winding 1 also has top and bottom layers, with the double-layer flexible PCB substrate 13 serving as the interface between the top and bottom layers.

[0027] During wiring, it is necessary to use etching technology and photo-imaging graphics to print the winding on the double-layer flexible PCB substrate 13, and curl the printed double-layer flexible PCB winding 1 according to the size of the designed slotless permanent magnet motor stator yoke. When curling, attention should be paid to good insulation between layers. Finally, the curled flexible PCB winding is bonded to the stator yoke circle of the slotless permanent magnet motor using metal glue. Finally, current is passed through the three terminals of the A, B, and C three-phase windings of the flexible PCB winding 1 to establish the stator magnetic field of the slotless permanent magnet motor.

[0028] Since the number of loops of the flexible PCB hexagonal winding is too large when it is unfolded, in order to simplify the model and not affect the analysis, only two loops of the hexagonal winding are taken as an example, as shown in the figure below. Figure 4 、 Figure 5 The flexible PCB winding 1 is arranged in a hexagonal stacked winding pattern, and the six sides of the hexagonal winding are sequentially designated as segments I, II, III, IV, V, and VI, with segments II and V being of equal length, and segments III and IV being of equal length. Figure 6 As shown; the windings of sections I, II and III are located on the top layer of the double-layer flexible PCB substrate 13, and sections IV, V and VI are located on the bottom layer of the double-layer flexible PCB substrate 13.

[0029] The flexible PCB winding 1 is applied to a radial flux slotless permanent magnet motor, and adopts a three-phase star-connected power supply method of A, B, and C. The size of the slot 2 varies for different flexible PCB windings 1. When the width of section II of the hexagonal winding is denoted as b and the width of section III is denoted as c, the length x of the slot 2 is equal to the length of section II of the hexagonal winding, i.e., x=b. The width y of the slot 2 is equal to the difference between the lengths of sections II and III of the hexagonal winding, i.e., y=bc. The depth z of the slot 2 is equal to the thickness of the copper foil 11. When the wiring inclination angle of the hexagonal winding is denoted as β, the width y of the slot 2 satisfies the formula y=b(1-sinβ), and 0°<β<90°.

[0030] Take winding sections II and III as an example. Due to the geometric characteristics of the hexagonal winding, sections II and III are not perpendicular to each other. Instead, the vertical lines of sections II and III differ by an angle, which is the wiring tilt angle β. As can be seen from the geometric relationship, the presence of the wiring tilt angle β causes the width of section II to be greater than that of section III. Given a constant thickness of the winding copper foil 11, this results in the current density of section II being lower than that of section III. To ensure that the current density of sections II and III is consistent, it is necessary to maximize the utilization of the copper foil 11 while simultaneously reducing the eddy current effect of the flexible PCB winding 1. Therefore, a slot 2 is created in the wider section II, with the width y of the slot 2 being equal to the difference in length between sections II and III of the hexagonal winding. This ensures that the current density of sections II and III is consistent while also reducing the area of ​​the winding exposed to the radial magnetic field, thereby reducing the eddy current effect of the flexible PCB winding 1. At this point, the utilization rate of the copper foil 11 is maximized. The same applies to the remaining winding sections. In addition, the slot 2 is located on the center line of each section II and section III of the flexible PCB winding 1. When the slot 2 is positioned, the copper foil 11 is cut at the positioning position to form a slot 2 with a thickness equal to that of the copper foil 11. Figure 7 、 Figure 8 shown.

[0031] When the width b of the II section of the hexagonal winding is selected, the formula b=I / (t×J) is satisfied, where I is the required motor winding current, J is the required motor winding density, and t is the thickness of the copper foil 11; when the width c of the III section of the hexagonal winding is selected, the formula b=I / (t×J) is satisfied, where I is the required motor winding current, J is the required motor winding density, and t is the thickness of the copper foil 11;

[0032] When selecting, the formula c=b×sinβ is satisfied, where b is the width of the II section of the hexagonal winding and β is the wiring inclination angle of the hexagonal winding. When selecting the wiring inclination angle β of the hexagonal winding, 45° is preferred. The winding eddy current loss of the flexible PCB hexagonal slotted winding is (1-sinβ) when the slot is not opened. 2 times.

[0033] Specifically, for hexagonal windings, due to the presence of a wiring inclination angle β at both ends, winding section II is wider than winding section III. The difference in width between the two is related to the wiring inclination angle β. When selecting the width b of winding section II, it is necessary to first determine the winding current I based on the required motor performance and select an appropriate winding electrical density J. Then, the thickness t of the copper foil 11 is determined according to the manufacturer's requirements. Since the winding electrical density is equal to the ratio of the winding current I to the winding cross-sectional area, that is, J = I / (t×b), the width of winding section II can be determined by inverse solution: b = I / (t×J). Therefore, the selection of the width b of winding section II is related to the winding current I, the copper foil thickness t, and the winding electrical density J. When selecting the width c of the segment III winding, on the premise that the current density of the segment III winding is appropriate, it needs to be determined by the difference between the axial length of the motor winding and the length of the segment II winding and the wiring inclination angle β. Different choices are made for different situations. When the wiring inclination angle of the hexagonal winding is β, according to the triangle calculation rule, the width of the segment III winding c = b × sin β can be determined.

[0034] To minimize eddy current losses in the winding while maximizing copper foil 11 utilization, the current density in winding section II should be equal to that in winding section III. Specifically, the width of winding section III should be equal to the difference between the width of winding section II and the width of slot 2. This maximizes copper foil 11 utilization and maintains a constant current density in the winding. Therefore, the required slot width for slot 2 should be y = bc. When the hexagonal winding's wiring inclination angle is β, according to the triangle calculation rule, the width of winding section III, c = b × sinβ. The required slot width for slot 2 is y = bc = bb × sinβ = b(1-sinβ), with 0° < β < 90°. This means that the required slot width for slot 2 depends only on the width b of winding section II and the wiring inclination angle β, and not on the width c of winding section III. From the formula y = b(1-sinβ) and 0° < β < 90°, we can see that c < b, meaning that the width of winding section III will necessarily be narrower than that of winding section II. In addition, in the flexible PCB winding 1, the eddy current loss P of the winding eddy It is proportional to the square of the width of the winding copper foil 11. For the winding of section II, when there is no slot, the winding eddy current loss P eddy ∝b 2 , after slotting, the winding eddy current loss P′ eddy ∝b 2 (1-sinβ) 2 , so the ratio of eddy current loss before and after slotting is P' eddy / P eddy ∝b 2 (1-sinβ) 2 / b 2 =(1-sinβ) 2<1, that is, compared with the flexible PCB winding without slots, the eddy current loss will be reduced to the original (1-sinβ) after slotting. 2 times.

[0035] The solutions in the embodiments are not intended to limit the patent protection scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention is included in the patent scope of this case.

Claims

1. A flexible PCB hexagonal slot winding, characterized by: The invention comprises a flexible PCB winding and a slot. The flexible PCB winding uses a double-layer flexible PCB as a substrate, and the flexible PCB winding uses copper foil as a conductor. Vias are used on both sides of the substrate for electrical connection. The copper foil is printed on the flexible PCB. The flexible PCB winding is arranged in a hexagonal stacked winding pattern, with the six sides of the hexagonal winding being sequentially designated as segments I, II, III, IV, V, and VI. Segments II and V are of equal length, and segments III and IV are of equal length. The slot has a rectangular cross-section and is symmetrically distributed about the vertical centerline of each copper foil. The medium inside the slot is air. The slot is located on each copper foil of the flexible PCB winding and is formed by cutting the copper foil. The size of the slot varies for different flexible PCB windings; the length of the slot is equal to the length of section II of the hexagonal winding; the width of the slot is equal to the difference between the lengths of sections II and III of the hexagonal winding; the depth of the slot is equal to the thickness of the copper foil; when the wiring inclination angle of the hexagonal winding is denoted as β, the width of the slot is denoted as y and satisfies the formula y=b(1-sinβ), and 0°<β<90°, where b is the width of section II of the hexagonal winding; When the width of section II of the hexagonal winding is selected, the formula b=I / (t×J) is satisfied, where b is the width of section II of the hexagonal winding, I is the required winding current of the motor, J is the required winding density of the motor, and t is the thickness of the copper foil; when the width of section III of the hexagonal winding is selected, the formula c=b×sinβ is satisfied, where c is the width of section III of the hexagonal winding, b is the width of section II of the hexagonal winding, and β is the wiring inclination angle of the hexagonal winding.

2. The flexible PCB hexagonal slot winding according to claim 1, characterized in that: The flexible PCB winding is applied to a radial flux slotless permanent magnet motor, and the flexible PCB winding adopts an A, B, and C three-phase star-connected power supply mode.

3. The flexible PCB hexagonal slot winding according to claim 1, characterized in that: When selecting the wiring inclination angle of the hexagonal winding, β=45° is preferably selected.

4. The flexible PCB hexagonal slot winding according to claim 1, characterized in that: The eddy current loss of the flexible PCB hexagonal slot winding is (1-sin β ) 2 times, where β is the wiring tilt angle of the hexagonal winding.

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