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Transformer with 3D wound core
The document defines a transformer with a three-dimensional wound core, which is composed of three single wound core frames and offers a more efficient structure compared to traditional stacked core transformers. It highlights advantages such as reduced manufacturing costs, improved performance, and better energy efficiency, including a significant decrease in no-load current and noise. Overall, the innovation in core structure represents a shift towards more sustainable and economically viable transformer technology.
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Transformer with 3D wound core
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- 2. Definition (GB25438-2010) 1. Termsand definition Terms and definition in GB 1094.1, GB/T 2900.15 and below are applied in this standard. 2. Three dimensional wound core Core combined by three single wound core frames with the same size to form a 3D triangle. 3. Distribution transformer with 3D wound core Distribution transformer with magnetic circuit of 3D wound core
- 3. Structural analysis andevolution of core Innovation of core structure In traditional lamination stacked core with air gap, coupled magnetic circuit of A-C phase is 1/2 longer than that of A-B and B-C, so the magnetic circuit is not balance, reluctance of A-C phase is bigger. (See figure 1) When three-phase voltage is applied to the transformer, three-phase balanced flux ΦA, φB and φC are generated on the core. When three- phase balanced flux goes through unbalanced magnetic circuit, magnetic pressure on phase A and C is big, which affects three-phase voltage balance. Imbalance on the magnetic loop is a structural defect which cannot be overcome for transformer with plane core. Fig. 1 Structure of plane core
- 4. Plane wound coreis without seam, saving weight on 4 corners, which is suitable to single phase transformer. In 1940s, 500KVA transformer with wound core (shell type) in Moscow transformer factory. In 1960s, transformer with single phase wound core was applied in China. In 1986, the first 30kVA transformer with three-phase closed wound core was manufactured in Shanghai. In 1990s, industry equipment and technology were imported from Japan and Sweden to China, and trial production started. Plane core AC intersecting chain flux AB intersecting chain flux BC intersecting chain flux Saving 4 corners compared to stacked core
- 5. For symmetry ofthree-phase magnetic circuit – It has been… Yoke Yoke Core limb
- 6. Single frames andcombination Fig. 2 Arrangement of 3D cores and single frames
- 7. Compared with traditionaltransformer structure with lamination stacked core, transformer with 3D wound core is a kind of new and high performance transformer with more reasonable structure, better performance and lower producing cost. Great popularization and wide use of this transformer will greatly save sources of energy and material with remarkable economic profit. Therefore, this kind of transformer will catch general attention and interest. The whole 3D wound core is composed by three identical single frames, and three core limbs of the combined core are arranged in equilateral triangle. Each single frame is wound by several ladder shaped material strips continuously and orderly, and the cross section of wound single frame is near semicircle, and the combined cross section is quasi- polygon which is very close to a circle. Different size of ladder-shaped strips for winding single frame can be got by suit cut on special curve slitting machine. This kind of suit cut is without waste material, which is to say the utilization rate of material is 100% during suit cut.
- 9. Advantages in sixaspects Saving material and reducing manufacturing cost: 20% silicon steel and 5% wire can be saved compared with that of plane three-phase lamination stacked core with the same capacity, thus it obviously reduces manufacturing cost, which is very popular with any transformer manufacturer and customer. Improving performance: with the same core and magnetic flux density, no-load loss is reduced by around 15% compared with that of transformer with plane lamination stacked core. Greatly reducing no-load current: no-load current is reduced by 70~80% compared with that of transformer with plane stacked core. Reducing noise obviously: 10 decibel is reduced compared with that of transformer with plane lamination stacked core. (5 decibel reduced for open type) Improving production efficiency: for open type wound core, core winding and coiling winding can be carried out at the same time, which improves production efficiency by more than 50%; reparation is much easier. Three-phase balance: because of different three-phase magnetic path length, no-load loss on two side frames of the transformer with plane three-phase stacked core is 20% more than that on the central column; while no-load loss on three core limbs of the transformer with three-phase 3 D triangular wound core are the same because of the same magnetic path length of three core limbs, so three-phase balance is perfect.
- 10. Advantage ContinuousContinuous windingwinding AnnealingAnnealing IncreasingIncreasing magneticmagnetic performanceperformance and loweringand lowering technologytechnology coefficientcoefficient Reducingno-Reducing no- load currentload current Reducing no-Reducing no- load lossload loss SymmetricSymmetric al layoutal layout IndependentIndependent symmetricalsymmetrical looploop Three-Three- phasephase balancebalance No three timesNo three times harmonic waveharmonic wave FasteningFastening without airwithout air gapgap ReducingReducing noisenoise ShortShort magneticmagnetic circuitcircuit ReducingReducing load lossload loss High fill factorHigh fill factor and laminatedand laminated coefficientcoefficient
- 11. Advantages Open type coreOpentype core winding andwinding and coil windingcoil winding can be carriedcan be carried out at the sameout at the same time.time. Easy reparation ImprovingImproving efficiencyefficiency Lessen humanLessen human factor to havefactor to have stable qualitystable quality ManufacturinManufacturin g of core andg of core and windingwinding needs specialneeds special equipment.equipment. A little investment on equipment It is used forIt is used for thin materialthin material processing.processing. Product withProduct with highhigh performanceperformance and low lossand low loss SavingSaving materialmaterial Small size / light weight, loweringSmall size / light weight, lowering cost and good looking appearancecost and good looking appearance
- 12. Slitting machine, Rewindingmachine and Winding machine
- 13. Winding of singleframe is on the special winding machine for 3D wound core. While winding this kind of material strips, the winding machine can automatically finish a 30 degree angle with precision on material to assure the well binding between surfaces on combining three single frames.
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- 15. Alignment of threewindows
- 16. Annealing under vacuum During manufacturingof wound core, as silicon steel experienced transportation, loading and unloading, slitting and winding process, stress generates on the cold-rolled silicon steel and then affects its magnetic performance. To recover its grain orientation and realize ordered arrangement of the grain inside the steel and to recover its magnetic performance as much as it leaves factory, stress shall be removed under the condition that insulation coating is not damaged, and the core needs annealing. During annealing, there is no phase change on silicon steel, no grain size change or structure change, only magnetism is recovered. Verified by testing, no-load loss on the core after annealing is reduced obviously. Rising time Preserving time Cooling down time Temperature
- 17. Annealing under vacuum Annealingis mostly affected by annealing equipment, temperature, time (temperature rising, preserving and decreasing), silicon steel grade, and quantity put in oven, core diameter, atmosphere in oven, which makes technology coefficient of core loss with large dispersion. Annealing consumes large quantity of power.