Foil winding structure of low voltage winding of a transformer
By adopting a segmented slotted metal foil winding structure with insulating paper isolation in the low-voltage winding of the transformer, the problems of high eddy current loss and squeeze current effect are solved, resulting in lower loss and more uniform temperature distribution, and improving the insulation performance and life of the winding.
Patent Information
- Application Number
- CN202522276145.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-28
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2035-10-28
AI Technical Summary
Traditional transformer low-voltage windings suffer from high eddy current losses, significant skin effect, severe current squeezing effect, and uneven heat distribution under high current conditions, leading to winding overheating and shortened lifespan.
The metal foil winding structure with segmented slotting is combined with insulating paper and laser slotting technology. By setting segmented slots on the metal foil and insulating paper for isolation, the current distribution is optimized and the heat conduction path is maintained, thereby reducing eddy current loss and squeezing effect.
It effectively reduces eddy current losses, balances temperature distribution, improves current distribution, and enhances the insulation performance and lifespan of the windings.
Smart Images
Figure CN224682938U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of transformer manufacturing technology, specifically to a foil winding structure for a transformer low-voltage winding. Background Technology
[0002] Traditional transformers typically use copper or aluminum foil for their low-voltage windings. For large-capacity transformers, due to the higher current, a single, thicker foil or multiple foils (two or more) are often directly stacked to increase the conductor cross-sectional area. However, this also results in a larger foil thickness. Figure 5 As shown. Since transformers transmit alternating current, the current distribution exhibits a skin effect. The thicker the winding, the more pronounced the skin effect, and the higher the frequency, the more pronounced the skin effect. At the same time, due to the alternating leakage magnetic field, eddy currents are induced inside the copper foil. The thinner the low-voltage foil winding, the more likely the eddy currents will form small-scale local loops, significantly reducing the induced voltage (smaller loop area) and thus drastically reducing losses.
[0003] Furthermore, since the low-voltage coil is located inside the winding, the alternating leakage magnetic field causes a current-squeezing effect in the copper foil current. The current concentrates at the edges of the foil, leading to increased local current density at both ends. This current-squeezing effect becomes more pronounced with increasing foil width under power frequency conditions. Figure 6 As shown.
[0004] This leads to overheating at both ends of the winding (especially the upper end), affecting the transformer's lifespan. Traditional continuous foil winding structures struggle to effectively suppress the current squeeze effect, particularly near the core side where uneven current distribution becomes more pronounced.
[0005] In existing technologies, to address the increased losses and overheating at both ends caused by the squeeze-flow effect, attempts are made to divide the foil into upper and lower segments using two foils spliced together to reduce the width. When splicing foils, a process gap must be left between the upper and lower foils. However, this gap hinders heat conduction between the upper and lower foils, increasing the temperature difference and affecting the winding's lifespan and performance. Figure 7 As shown.
[0006] To address this, a foil winding structure for the low-voltage winding of a transformer is proposed. Summary of the Invention
[0007] The purpose of this invention is to provide a foil winding structure for the low-voltage winding of a transformer to solve the problems mentioned in the background art.
[0008] To achieve the above objectives, this utility model provides the following technical solution: a foil winding structure for a transformer low-voltage winding, comprising stacked metal foils, with end insulating layers at both ends of the metal foils, insulating paper between the stacked metal foils, and at least one slotted portion on the metal foils, the slotted portion being a segmented slot, the slotted portion including multiple slots evenly distributed in a straight line.
[0009] Preferably, the slot width is 0.5-1mm, the slot length L1 accounts for 60%-80% of the length L of a single foil segment, and the unslotted area L2 accounts for 20%-40% of the length L of a single foil segment.
[0010] Preferably, the thickness of the insulating paper is 0.05 to 0.2 mm, and the insulation class of the insulating paper is greater than or equal to the insulation class of the winding itself.
[0011] Preferably, when the number of slotted portions is one, the slotted portion is located in the middle of the metal foil (1).
[0012] Preferably, when there are two or more slotted sections, the slotted sections are distributed in parallel, and the slots in the slotted sections are staggered vertically.
[0013] Preferably, the slot is created using a laser grooving process.
[0014] Preferably, the metal foil is copper foil or aluminum foil.
[0015] Compared with the prior art, the beneficial effects of this utility model are:
[0016] 1. Reduce eddy current loss: By separating the overlapping foil with insulating paper and segmenting the slots, the eddy current loss is effectively reduced, thus reducing the decrease in current carrying capacity caused by the skin effect.
[0017] 2. Balanced temperature distribution: The intermittent slotting design reduces the foil width while retaining the heat conduction path, avoiding excessive temperature difference between the upper and lower foils.
[0018] 3. Improve the current squeeze effect: By segmenting the grooves, the current distribution is optimized, the current accumulation at both ends of the foil is reduced, and the local temperature rise is reduced.
[0019] 4. Process reliability: Laser grooving leaves no burrs, improves insulation performance, and reduces the risk of partial discharge. Attached Figure Description
[0020] Figure 1 This is a cross-sectional schematic diagram of the folded structure of this utility model;
[0021] Figure 2 This is a schematic diagram of the structure of a single slotted portion of this utility model;
[0022] Figure 3 This is a schematic diagram of the structure of the multi-grooved part of this utility model;
[0023] Figure 4 This is a schematic diagram of the structure of this utility model after the density of the slots at both ends is increased;
[0024] Figure 5This is a schematic diagram of the existing technology;
[0025] Figure 6 This is a schematic diagram of the metal foil extrusion effect;
[0026] Figure 7 This is a schematic diagram of the traditional top-and-bottom foil splicing process.
[0027] In the diagram: 1. Metal foil; 2. Insulating paper; 3. End insulation layer; 4. Slot; 5. Groove section. Detailed Implementation
[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.
[0029] Please see Figure 1-4 This utility model provides a technical solution: a foil winding structure for a transformer low-voltage winding, including stacked metal foil 1, the metal foil 1 being copper foil or aluminum foil, with end insulation layers 3 at both ends of the metal foil 1, and insulating paper 2 between the stacked metal foils 1. Two metal foils 1 are stacked, with 0.05-0.2mm of insulating paper 2 sandwiched in between. The insulating paper 2 is used to separate the layers, reducing the equivalent thickness and lowering eddy current losses. The total coil height ≥ the width of the insulating paper 2 > the width of the metal foil, ensuring effective electrical isolation while maintaining the flatness of the coil ends. Figure 1 As shown. Meanwhile, the insulation class of the insulating paper 2 needs to be the same as or greater than the insulation class of the winding itself to avoid transformer damage due to insulation aging.
[0030] The metal foil 1 has at least one slotted section 5, which is a segmented slotting section, including multiple slot holes 4 evenly distributed in a straight line. The width of the slot holes 4 is 0.5 to 1 mm, the slot length L1 accounts for 60% to 80% of the length L of a single foil segment, and the unslotted area L2 accounts for 20% to 40% of the length L of a single foil segment. The segmented slotting is an intermittent and discontinuous slotting method, which retains part of the unslotted area to maintain the heat conduction path between the upper and lower foils. By segmenting the slotting, the current distribution path is changed, reducing the current concentration at both ends of the metal foil 1, thereby reducing local overheating caused by the current squeeze effect.
[0031] Slot 4 is made using laser grooving. Traditional mechanical grooving methods such as stamping and milling are prone to defects such as metal burrs and wavy edges. Furthermore, since the grooving position is in the middle of the foil, it is impossible to perform mechanical grinding and chamfering on a production line.
[0032] Burrs can cause local electric field distortion, increasing the risk of partial discharge. Wavy edges can cause the foil to not adhere properly during winding, increasing the radial dimension of the winding.
[0033] The laser grooving process uses a high-energy laser beam to directly vaporize materials (such as copper or aluminum foil) without physical contact or cutting force, thus fundamentally eliminating burrs caused by mechanical extrusion.
[0034] During laser scanning, the small amount of molten metal at the edge of the groove forms a smooth surface (similar to "vitrification") after cooling, while mechanical cutting leaves tear-like burrs.
[0035] Example 1
[0036] Please see Figure 2 The metal foil 1 is a copper foil or an aluminum foil. The upper and lower ends of the metal foil 1 are provided with end insulation layers 3. Insulating paper 2 is provided between the stacked metal foils 1. A slotted part 5 is opened on the metal foil 1. The slotted part 5 is located in the middle of the metal foil 1. The slotted part 5 is a segmented slotting. The slotted part 5 includes multiple slot holes 4 that are evenly distributed in a straight line.
[0037] For scenarios where the eddy current response is not significant, a slot 5 can be made only in the middle of the metal foil 1. The slot width 4 is 0.5-1mm, the slot length L1 accounts for 60%-80% of the length L of a single foil segment, and the unslotted area L2 accounts for 20%-40% of the length L of a single foil segment. This can balance reducing eddy current loss and balancing heat conduction, optimize current distribution to improve the eddy current effect, and effectively avoid the occurrence of strength reduction.
[0038] Example 2
[0039] Please see Figure 3 or Figure 4 The metal foil 1 is made of copper or aluminum foil. End insulating layers 3 are provided at both ends of the metal foil 1. Insulating paper 2 is provided between the stacked metal foils 1. Two or more slots 5 are formed on the metal foil 1. The slots 5 are parallel to each other, and the slot holes 4 in the slots 5 are staggered vertically. The slots 5 are segmented slots, and each slot includes multiple slot holes 4 evenly distributed in a straight line.
[0040] For cases where the squeeze effect is significant, multiple parallel slots 5 can be formed on the metal foil 1, such as... Figure 3 As shown, the multi-stage intermittent slotting design reduces the foil width while preserving the heat conduction path, thus avoiding excessive temperature differences between the upper and lower foils.
[0041] Furthermore, when the squeezing effect is more pronounced, the groove density can be increased near both ends of the metal foil 1, such as... Figure 4 As shown, this is to further disperse the edge current.
[0042] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A foil winding structure for a transformer low-voltage winding, comprising stacked metal foil (1), characterized in that: The metal foil (1) has end insulation layers (3) at both ends, and insulating paper (2) is provided between the stacked metal foils (1). At least one slot (5) is opened on the metal foil (1). The slot (5) is a segmented slot, and the slot (5) includes multiple slots (4) that are evenly distributed in a straight line.
2. The foil winding structure of a transformer low-voltage winding according to claim 1, characterized in that: The slot width of the slot (4) is 0.5 to 1 mm, the slot length L1 accounts for 60% to 80% of the length L of a single foil segment, and the unslotted area L2 accounts for 20% to 40% of the length L of a single foil segment.
3. The foil winding structure of a transformer low-voltage winding according to claim 1, characterized in that: The thickness of the insulating paper (2) is 0.05 to 0.2 mm, and the insulation class of the insulating paper (2) is greater than or equal to the insulation class of the winding itself.
4. The foil winding structure of a transformer low-voltage winding according to claim 1, characterized in that: When the number of the slotted portions (5) is one, the slotted portions (5) are located in the middle of the metal foil (1).
5. The foil winding structure of a transformer low-voltage winding according to claim 1, characterized in that: When the number of slotted portions (5) is two or more, the slotted portions (5) are distributed in parallel, and the slot holes (4) in the slotted portions (5) are staggered vertically.
6. The foil winding structure of a transformer low-voltage winding according to claim 1, characterized in that: The slot (4) is created using a laser grooving process.
7. The foil winding structure of a transformer low-voltage winding according to claim 1, characterized in that: The metal foil (1) is either copper foil or aluminum foil.