Dry-Type Transformer Temperature Controller

Balancing Heat and DissipationStable Temperature Rise of the Winding

Loss power on the winding is the heat source for winding temperature rise.,This is quite calculable..The heat dissipation of the winding is a relatively complex issue..Heat within the winding is transferred to the winding's surface through conduction.,Heat is transferred to the external environment through convection and radiation on the surface..When the heating and cooling of the winding reach a balance.,It's the stable temperature rise of the winding.

Winding heat dissipation is a complex process. Key factors affecting winding heat dissipation include: winding temperature; insulation thickness; external insulation thickness of the winding; thermal conductivity of the external insulation material; width and length of the heat dissipation channels; air flow speed; and the impact of the core and adjacent windings on heat dissipation. Therefore, the winding temperature rise calculation varies depending on the insulation material and structure used.

Mathematical Model for Winding Temperature Rise Calculation

The stable temperature rise of windings is generally calculated using a simplified formula.,Winding coefficients for different structures and insulating materials vary. The temperature range applicable for 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

 W— Winding Loss Power at Reference TemperatureW

 S— Equivalent thermal surface aream2

 SiInsulated winding heat sinkm2

 αiThermal Conductivity

2.1 Transformer calculation formulas vary depending on their structural types.

2.2 The cooling of dry-type transformers is primarily achieved through convection and radiation, with the temperature rise due to conduction in non-encapsulated transformers being relatively minor. Consequently, some calculation formulas omit the temperature rise caused by conduction from layer insulation and external insulation, while others require the addition of the temperature rise due to conduction, such as the calculation formulas for European resin-insulated dry-type transformers.

2.3 Boldface Heat RadiationAbsolutely.Please provide the Chinese content to be translated.Temperature 4 Proportional to the square, within a relatively narrow temperature range, the combined effect of convection and radiation on heat dissipation results in a temperature rise coefficient.XCoefficient related to heat dissipation effect,Enhanced Heat DissipationX The value is smaller..As the temperature rise of the oil-immersed transformer's layer windingX Please provide the Chinese content to be translated.0.8Forcing oil circulationX Please provide the Chinese content to be translated.0.7Winding arrangementX No Chinese content provided.0.6Dry-type TransformerX Value obtained0.8When the temperature rises...80K At right angles, due to higher heat dissipation efficiency at higher temperatures, in some calculation formulasX Please provide the Chinese content to be translated.0.75Therefore, when the temperature rises...100—125K At the moment,X The value should be reduced further.

2.4 When the temperature range is wide, a single calculation formula may not be sufficient to address both ends; it requires two or more formulas, which...X The value differs, indicating different slopes. In reality, it is an approximate curve composed of several straight lines.

2.5 Unit heat load of the windingQ Power refers to the power on an uncovered unit surface area.W/m2To determine the heat dissipation coefficient of the vented surface, one must have an airtight design.

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.

Establishing a Factory Method for Mathematical Models

 A practical method for determining mathematical models is through the temperature rise test of a typical transformer. The temperature rise of the airless winding is fundamental, such as the outer winding wrapped around a thick insulating sleeve. The size of the area outside the coil is the effective heat dissipation surface, and the heat load is first calculated. Q Value, as determined by the temperature rise obtained from the testQ Please plot the values on a double logarithmic graph, 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 AndX。

τ= K Q X

 τ1

 K = ————

Q1 X

 Lgτ2 - Lgτ1 Lgτ2/τ1

 X =———————— = ————

 Lg Q2 - Lg Q1 Lg Q2/Q1

 In the formula:

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

 Q1，Q2—— Corresponding unit heat load

τ—the temperature rise of the product in question

 QUnit heat load of the desired product

To determine the equivalent heat dissipation surface of the inner coil and the surface with the airway, it's first necessary to ascertain the heat dissipation coefficient of the airway. Calculate the heat load. Q The value, obtained from the temperature rise in the tests, isQ Please place dots on a double logarithmic graph, at least3 A trial data, methods as above.

Note that this straight line is only acceptable within a certain temperature range for its deviation. Outside of this range, the slope of the line differs and is actually composed of a curve made up of many broken lines.

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