Dry-Type Transformer Temperature Controller

Balancing Heat and DissipationStable temperature rise of the winding

Loss power on the winding is the heat source causing the winding temperature rise.,This is rather easy to calculate..The heat dissipation of the winding is a rather complex issue..Heat within the winding is transferred to the surface of the winding through conduction.,On the surface, it is transferred to the external environment through convection and radiation..When the heating and cooling of the winding reach a balance.,The stability of the winding's temperature rise.

Winding heat dissipation is a complex process. Key factors affecting winding heat dissipation include: winding temperature; insulation thickness; winding sheath insulation thickness; the heat dissipation performance of winding sheath materials; the width and length of cooling air channels; air flow velocity; and the impact of core and adjacent winding heat dissipation. Therefore, winding temperature rise calculations vary depending on the type of insulation material and structure used.

Mathematical Model for Winding Temperature Rise Calculation

The stable temperature rise of the winding is generally calculated using a simplified formula.,Different structures and insulation materials have different winding coefficients. The temperature range applicable to the formula is also limited.:

τ＝ K Q X

Q ＝ W／S

S ＝∑ αi Si

 In the formula:τ—Winding temperature rise

K—Coefficient;

 XCoefficient related to heat dissipation,Superior heat dissipationX The value is smaller.

Q— Unit thermal load of the windingW/m2

 WWinding Loss Power at Reference TemperatureW

 S— Equivalent heat dissipation surfacem2

 SiInsulated winding heat sinkm2

 αiThermal Conductivity

2.1 Transformer calculation formulas vary depending on the structural type.

2.2 Dry-type transformers dissipate heat primarily through convection and radiation. The proportion of temperature rise due to conduction in non-encapsulated transformers is minimal, so some calculation formulas omit the temperature rise caused by conduction from layer insulation and external insulation. Some formulas, however, require the addition of the temperature rise due to conduction, such as the calculation formulas for European resin-insulated dry-type transformers.

2.3 Bold-faced thermal radiationAbsolutely.No Chinese content provided. Please provide the text to be translated.Temperature 4 Proportionally squared, within a relatively small temperature range, the combined effect of convection and radiation on heat dissipation results in a temperature rise, with the coefficient in the temperature rise equation.XCoefficient related to heat dissipation effect,Enhanced Cooling PerformanceX The value is smaller..As the temperature rise of the layer winding of oil-immersed transformerX Please provide the Chinese content for translation.0.8Thereby forcing oil circulation.X Take0.7Pie-shaped windingX Take0.6. General dry-type transformerX Please provide the Chinese content to be translated.0.8Please provide the Chinese content to be translated.80K At right angles, due to high thermal dissipation efficiency at high temperatures, in some calculation formulas...X No Chinese content provided.0.75Due to the increase in temperature, therefore, when warming up100—125K At the time,X The value should be smaller.

2.4 When the temperature range is wide, a single calculation formula may not cover both ends adequately; it requires two or more formulas, which...X Value differences, or varying slopes. In reality, it is an approximate curve composed of several straight lines.

2.5 Unit thermal load of the windingQ It refers to the power on an uncovered unit heat dissipation surface.W/m2If there is an aerated heat dissipation surface, it is necessary to determine the heat dissipation coefficient of the airways.

2.6 If the calculated temperature rise is significantly different from the reference temperature, and the discrepancy between the calculated winding loss power and the actual power is too great, resulting in a large error, then the reference temperature used to calculate the winding loss power should be adjusted.

Factory Method for Determining Mathematical Models

 A practical method for determining mathematical models is through temperature rise tests on typical transformers. The temperature rise of the non-air-core winding is fundamental, such as the outer winding wrapped around a thick insulation sleeve. The size of the area outside the coil represents the effective heat dissipation surface, and the heat load is calculated first. Q Value, as determined by the temperature rise obtained from the testQ Plot values on a double logarithmic coordinate paper, at least.3 A set of experimental data can be plotted as a reasonable straight line on a logarithmic coordinate paper, from which the two coefficients of the formula can be determined.K No Chinese content provided.X。

τ= K Q X

 τ1

 K = ————

Q1 X

 Lgτ2 - Lgτ1 Lgτ2/τ1

 X =———————— = ————

 Lg Q2 - Lg Q1 Lg Q2/Q1

 Please provide the Chinese content to be translated.

 τ1，τ2——Increase the temperature rise of two products along the straight line

 Q1，Q2—— Corresponding unit heat load

T——temperature rise of the desired product

 Q—— Unit heat load of the sought product

To determine the equivalent heat dissipation surface of the inner coil and the surface with the airway, it is first necessary to ascertain the heat dissipation coefficient of the airway. Calculate the heat load. Q Value, as determined by the temperature rise obtained from the testQ Please place values on the log-log coordinate paper, at least.3 A trial data, methods as same as above.

It should be noted that this line is only acceptable within a certain temperature range for the error margin. Outside of this range, the slope of the line is different, actually consisting of a curve composed of many broken lines.

Another point to note is that the calculated surface area for heat dissipation must match the actual manufacturing.