2. Reduce the overlapping width of iron core and reduce the no-load loss of iron core
At the corner of the core lamination, the overlapping width of the joint area between the core column and the cross yoke has a certain impact on the no-load function of the transformer. If the overlapping area is large, the area through which the magnetic flux passes will increase accordingly, and then the no-load loss will increase. According to the iron core model experiment, the no-load loss of 45 ° joint will increase by 0.3% for every 1% of the lap area. To reduce the no-load loss, it is necessary to study and select the best lap area with no-load loss and mechanical strength on the premise of meeting the mechanical strength.
By changing the connection area of the laminated tower of the iron core, reducing the size of some triangular holes in the iron core and reducing some magnetic flux density at the triangular holes, the no-load loss of the transformer can be reduced. The original angle of iron core lamination of our company's distribution transformer is 10mm, but now it has been changed to 5mm, which has achieved certain consumption reduction. The outlet angle of the iron core lamination is changed from 10mm to 5mm, so that the cross-sectional area of the triangular hole at the corner of the iron core is added, and some magnetic flux density at the triangular hole must be reduced.
3. Reasonably select the iron chip width, reduce the iron core angular weight, 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 no-load loss of the transformer.
The preconditions for discussing the rules of iron chip width selection and iron core angle weight change are:
(1) The number of stages of the iron core must be equal.
(2) The diameter of the iron core is D, and the main stage sheet width of the iron core shall be selected according to D minus 5mm or 10mm. Unequal core diameters are formed by the sheet width and stack thickness at all levels. The maximum first-order difference between the two cores is controlled below + 0.3mm, that is, the winding package cannot be affected due to the out of tolerance of core diameter.
(3) The useful cross-sectional area of iron cores with different sheet shapes is equal in theory.
This is intended to ensure that the same flux density is selected and the same unit iron loss is obtained.
(4) The slice width and stack thickness of the core column section are necessary to be in common with the core yoke section.
In the planning process, when selecting the sheet width of the main stage iron core after confirming the appropriate core diameter, it is advocated that the effect of selecting the sheet width D minus 10mm is better than that of D minus 5mm. Its advantages are as follows:
① The slice width at all levels decreases step by step;
② Under the condition of keeping the useful cross-sectional area of the iron core flat, the angular weight of the iron core is reduced;
③ The height of the iron core is reduced by 10mm, the overall height of the oil tank is also reduced by 10mm, and the materials of the transformer are also saved
