What Are The Factors That Affect Transformer Loss? How To Reduce?

A method to reduce no-load loss
No-load loss is an important parameter of transformer, accounting for 20%~30% of the total transformer loss. In order to reduce no-load loss, it is necessary to reduce the total core, unit loss and process coefficient. The main ways to reduce no-load loss are as follows:

(1) Adopt high permeability silicon steel sheet and amorphous alloy sheet. Ordinary silicon steel sheet thickness 0.3~0.35mm, low loss, can be used 0.15~0.27mm. At the same time, if the step stacking is used, the iron loss can be reduced by about 8%. Laser irradiation, mechanical indentation and plasma treatment can reduce the loss of high permeability silicon steel sheet. The eddy current loss of amorphous alloy sheet and silicon steel sheet with silicon content of 6.5% is less than that of common high permeability silicon steel sheet.

(2) Reduce the process coefficient. Process loss coefficient is related to many factors such as silicon steel sheet material, annealing of punching and shearing equipment, clamping degree and so on. It is also very important to adjust the tool accuracy of punching and shearing equipment reasonably.

(3) Improve the core structure. The core is not punched, the glass tape is not bound, the end face is coated with curing paint, and the interphase is bound with high-strength steel tape. The drawing plates connecting the upper and lower clips on both sides of the core column are made of non-magnetic steel plates. Large capacity iron chips are not painted to improve filling coefficient and cooling performance. The two yoke of the iron core are made of forced tooling and adhesives to form a solid, flat, vertical and high precision whole. Reducing the lap width of the core can reduce the loss. For every 1% reduction in lap area, no-load loss will be reduced by 0.3%. The different brands of silicon steel sheets in the core will consume energy, so it should be mixed less or not mixed.

(4) Reduce the size of the core window. Change the winding insulation (thickness) from constant turn to variable turn insulation. For example, according to the impact voltage distribution 120,000/110 transformer, the turn insulation thickness of one end of the high voltage winding and the regulating section is 1.35mm, and the other sections are 0.95mm. Therefore, after reducing the window size, the iron weight is reduced by 1.67%. Under the premise of safety, reasonably narrow the distance between the high and low main air passage, reduce the oil passage between the cake, narrow the distance between the phases, and strengthen the insulation treatment (add corner rings, partitions, etc.). The winding adopts half oil passage structure to shorten the center distance, iron weight and iron loss of the core column.

(5) Design a non-resonant core. The resonance frequency of the iron core is designed in the appropriate frequency segment, so that it can not produce strong resonance, and the noise reduction effect is obvious, and the energy used for noise reduction can be saved.

(6) Coil core transformer and three-dimensional core transformer. The rolled core has four fewer sharp corners than a traditional laminated core. Continuous winding makes full use of the positioning of the silicon steel sheet and adopts the annealing process to reduce additional losses. For R-coil core, the section duty cycle factor is close to 100%. The yoke of the three-dimensional core is triangular in shape and 25% lighter than that of the flat-rolled core. These factors indicate that rolled and three-dimensional cores are more energy efficient.

2. Methods to reduce load loss
The load loss accounts for 70% to 80% of the total loss, including winding DC resistance loss (basic loss), wire vortex loss, interwinding circulation loss, wire loss and structural parts (such as splints, steel platen, box wall, bolts, iron core pull plate, etc.). The main ways to reduce load loss are as follows:

(1) Limit the additional loss caused by magnetic leakage. Calculate the ampere-turns balance and adjust the ampere-turns according to the result; The winding adopts low-high-low or high-low-high arrangement; Limit the width and thickness of the flat line; Select the most suitable transposition method according to the magnetic field; Use transposition wires or combination wires.

(2) Reduce the size of the main insulation and longitudinal insulation structure. The high voltage winding adopts equal impulse voltage gradient distribution technology, which can reduce the size of longitudinal insulation. Thin paper tube and small oil gap are adopted between windings. Corrugated paper is the main insulation; The shape of the forming part is exactly the same as that of the equipotential, the shape of the corner ring is consistent with the shape of the equipotential line, and the split corner ring is used as the structural part; The inner diameter of the winding is wound on the insulating paper, but the middle of the line segment is provided with an axial oil passage; More acetal enamelled wire is used, and QQ-2 or QQB acetal wire is used instead of 0.45mm thick paper-wrapped flat wire. Because the insulation of the first two turns is 2×(0.056~0.079) mm, the filling coefficient of the winding is high, which meets the requirements of the turn insulation; Most of them use cylindrical winding. Because there is no oil passage between cakes, the cooling mainly depends on the axial vertical oil passage, good heat dissipation, good filling coefficient and impact characteristics, uniform turns, and small short circuit force; Appropriately reduce the distance between the main insulation (diameter, end).

(3) The relevant process is adopted according to the calculation. According to the impact calculation, it is determined that the vertical insulation structure, pad, support and metal chamfer are in good shape; Calculate the leakage magnetic field and eddy current distribution to guide the transposition mode; The winding axial distribution is uniform, and the core strap is made of non-magnetic material. The core column and yoke iron parts are provided with special shielding to alleviate the electric field; The pressure regulating winding is separated layer by layer. The process is assembled, the inner winding is directly wound on the insulation cylinder, the height is strictly controlled, the diameter tolerance is small, the set gap is small, the hot sleeve new process is adopted, the whole tray and pressure plate are used, the winding is transposed by Dinison paper, with pressure drying, and the winding is placed in the insulated drying room to prevent moisture.

(4) Use low loss and low resistance wires. Use up drawing to pull out oxygen-free copper wire, such as copper continuous extrusion press. If it can be used in transformers, it can save energy and reduce volume, and has certain application prospects.

(5) Using the characteristics of the insulation structure design can reduce the volume. Cover layer, barrier, shield and insulation layer are set appropriately by using the characteristics of transformer oil liquid dielectric; The separator is added to the small oil gap by using the distance effect of oil. Using the volume effect of oil using corrugated paper; Use the thickness effect of insulating layer in oil to increase insulation and increase breakdown voltage, but not too thick; The separator is set by using the maximum field strength distance characteristic of the separator in the oil.

(6) Advanced insulation structure. The suitable winding is adopted to improve the filling coefficient, and the new spiral (or continuous) winding is adopted in the axial oil passage to effectively reduce the winding volume. The compression structure of non-metallic or non-magnetic materials is used for the magnetic flux leakage concentration part, and the magnetic flux leakage groove is routed with electromagnetic shielding, and the load loss can be reduced by 3% to 8%.

(7) Preferred winding internal protection. Internal winding protection measures include capacitor rings, static wire turns, series compensation (additional cake capacitor), equal potential screen, tangled winding or internal shield winding. They all have the ability to reduce overvoltages used for primary and longitudinal insulation under shock, thereby reducing the volume and energy consumption of the transformer.

(8) The long circular winding is connected with Yyn0 to reduce the height and energy saving. Using an oblong iron core, winding or oval winding or rectangular winding with rounded corners is in practice more energy efficient than a traditional circular section. Yyn0 is lower than the connector connected by Dyn11, and the three can share a disc connector switch, which has simple structure and small volume. The former is 2% heavier than the latter for 500kVA transformers, iron is 6% heavier, oil is 11% heavier, saving materials and energy. For dry transformers, the higher the winding, the more obvious the upper and lower temperature difference, which is conducive to heat dissipation and energy saving.

3. Methods to reduce stray losses
Stray loss is a special case of load loss, so the methods to reduce it are discussed separately. The stray loss includes the loss of structural parts (core clips, shielding rings, etc.). Loss through the conductor (casing holder); Losses of parallel conductors (through high-current wires) and losses of fuel tanks. There are several main ways to reduce stray loss:

(1) According to magnetic analysis and physical measurement, the use of small core clips, cancel the single-phase center column core plate, increase the gap on the core surface, and use low magnetic or non-magnetic materials for the core pull plate and the structural parts (such as bolts) in the leakage field, which can reduce the stray loss of the internal structure.

(2) For the casing outlet box and part of the box cover, carefully configure the wire to control the magnetic field, using copper plate shielding or non-magnetic material, casing cover is made of aluminum. The silicon steel plate platen can also be arranged between the winding and the clamp to absorb the magnetic flux between the clamp and the tank. The strapping non-ferrous metal is buried in the place where the magnetic field is strongest, which can reduce the stray loss of the high-current bushing and wire part. (3) For large transformers, magnetic shunt is carried out along the built-in silicon steel plate with high permeability along the box wall, and the absorption of the box wall magnetic flux is called magnetic shielding; Or use non-ferrous metals with high conductivity copper and aluminum as lining to generate eddy current reaction and reduce magnetic leakage and weighing shielding into the tank wall. In general, magnetic shielding is better than electrical shielding, which can reduce the stray loss of the tank.

(4) Quantitative calculation of the oil flow loop, the use of baffles, reasonable separation of windings, uniform cooling, optimization of corrugated oil tank, chip radiator, cooler, energy-saving fan, oil pump, to obtain the most economical energy-saving cooling less stray loss.

(5) Glass fiber reinforced plastic fan, high efficiency, low noise. Replacing the old cooler with a new cooler and adopting a variable frequency power supply cooler can reduce the loss of auxiliary equipment.