Analysis of Heating Causes in Power High-frequency Transformers

The heating causes of power high-frequency transformers share some similarities with those of conventional transformers. However, due to their operation at much higher frequencies, there are also some unique causes of heating. Below are some of the main causes of heating in power high-frequency transformers:

High-frequency switching losses:

High-frequency transformers are typically used in switching power supplies, with operating frequencies ranging from tens of kilohertz to several megahertz. During the high-frequency switching process, the current and voltage in the windings change rapidly, leading to increased switching losses. These losses are mainly manifested as resistive losses in the windings and additional losses generated during the switching instant.

High-frequency iron losses:

The core material used in high-frequency transformers experiences more significant hysteresis and eddy current losses in an alternating magnetic field compared to low-frequency transformers. The increase in frequency accelerates the rate of flux change, leading to increased hysteresis losses. Meanwhile, eddy current losses also increase due to the higher frequency.

Increased AC resistance of windings:

At high frequencies, the AC resistance of the windings is higher than the DC resistance due to the effects of skin effect and proximity effect. These effects cause the current to concentrate on the surface of the windings, reducing the effective cross-sectional area and thereby increasing resistance and heating.

Insulation material losses:

The insulation materials in high-frequency transformers may generate more dielectric losses under high-frequency electric fields, which are also converted into heat.

Improper design:

If the structure of the transformer is poorly designed, such as insufficient winding spacing, excessive winding layers, or improper core material selection, it may lead to poor heat dissipation and increased losses.

Manufacturing process issues:

Problems in the manufacturing process, such as winding, layer insulation treatment, and core lamination, can all lead to increased losses and poor heat dissipation in the transformer.

Load condition changes:

Changes in the load conditions of a high-frequency transformer, such as increased load current or load power fluctuations, can also increase the heat generation of the transformer.

Environmental factors:

High ambient temperatures or poor heat dissipation conditions (such as fan failure or dust accumulation on heat sinks) can also lead to temperature rise in the transformer.

To address the heating issues of high-frequency transformers, the following measures can be taken:

Select appropriate core materials and winding wire materials to reduce hysteresis and eddy current losses.

Optimize winding design, such as using multi-strand parallel winding and segmented winding methods, to reduce AC resistance.

Improve insulation materials and structures to reduce dielectric losses.

Enhance heat dissipation design, such as increasing heat dissipation area and using efficient heat dissipation materials.

Regular cleaning and maintenance to ensure the normal operation of the cooling system.

Monitor operational status and promptly detect and address abnormal load conditions.