Methods to reduce no-load loss of electrical substation transformer

Through the analysis of no-load loss, the hysteresis loss and eddy current loss of the iron core are mainly determined by the silicon steel sheet manufacturer, and the additional loss is determined by the electrical substation transformer manufacturer. The magnetic flux density of the iron core is an important parameter that affects the no-load loss of the transformer core. Therefore, to reduce the no-load loss, the magnetic flux density distribution of each part of the iron core must be uniform under the premise that the effective section of the iron core remains unchanged. , reducing the local magnetic flux density at the corners of the core.

1. Staggered seams are changed to third-order seams

Since there is a gap in the joints of the transformer iron core silicon steel sheets, the magnetic resistance suddenly increases when the magnetic flux passes through the joints. The increase in the magnetic resistance across the inter-chips also increases the local magnetic density of the adjacent laminations, resulting in an increase in no-load loss and excitation capacity.

The more the seam series of the electrical substation transformer core, the lower the local loss in the seam area, but the smaller the reduction of the local loss. The crafting difficulty of the sheet will increase as the seam progression increases.

In practice, considering that with the increase of the number of stages, the cutting time of the silicon steel sheet and the stacking of the iron core increase accordingly, and the lamination process becomes worse. Considering that if a three-level seam is used, a suitable sheet type is selected, and only one sheet type is added to the core column, the process complexity is slightly increased, and the magnetic properties are significantly improved. The three-level seam of the iron core is formed by alternating stacking of three types of laminations. According to the technical level of the metallurgical electric repair enterprise and the magnetic performance data of the joint, the use of three-level joint is an ideal choice for improving the staggered joint iron core.

Taking the S9-800/10 and S9-1000/10 power transformers as examples, the same type of transformer adopts the same design scheme, structure and material, and the iron core adopts different lap joint methods. Class seam, 1000kVA 2 units adopt staggered seam, 3 units adopt tertiary seam.

Through the test data, it can be concluded that the no-load loss of the three-level joint is reduced by about 7% to 8% on average compared with the staggered joint when the cross-section of the core column remains unchanged. The tertiary seam is only a sheet type added to the core column, and the shearing of the silicon steel sheet and the stacking time of the iron core are slightly increased, but the results are remarkable.

2. Reduce the lap width of the iron core and reduce the no-load loss of the iron core

At the corners of the core laminations, the lap width of the joint area between the core leg and the transverse yoke has a certain influence on the no-load performance of the transformer. The larger the overlap area, the larger the area through which the magnetic flux passes, resulting in an increase in no-load loss. According to the iron core model test, the no-load loss of the 45° joint will increase by 0.3% for every 1% increase in the overlap area. To reduce the no-load loss, it is necessary to study the selection of the optimal lap area for both no-load loss and mechanical strength under the premise of satisfying the mechanical strength.

Changing the tower connection area of the iron core stack, reducing the size of some triangular holes in the iron core, and reducing the local magnetic flux density at the triangular holes can reduce the no-load loss of the electrical substation transformer. Our companys distribution transformer originally had a lamination angle of 10mm, but now it has been changed to 5mm, which has achieved a certain effect of reducing consumption. The lamination angle of the iron core is changed from 10mm to 5mm, so that the cross-sectional area of the triangular cavity at the corner of the iron core increases, and the local magnetic flux density at the triangular cavity will inevitably decrease.

3. Reasonably choose the width of the iron core, reduce the corner weight of the iron core, reduce the iron core material, and reduce the no-load loss

The no-load loss of the iron core is related to the unit iron loss of the iron core and the weight of the iron core, and the angular weight of the iron core is a part of the weight of the iron core, so the angular weight of the iron core not only affects the cost of the transformer, but also directly affects the transformer. no-load loss.