Types And Causes of Energy Loss in Transformers

As a core device in the power transmission system, the energy loss of transformers directly affects the efficiency of the power grid and the operating cost. Energy loss mainly consists of iron loss and copper loss, and there are also some secondary losses. The following is a detailed analysis of the causes, influencing factors and optimization directions of various types of losses.

I. Iron Loss (No-load Loss)

Iron loss is the loss generated by a transformer under no-load conditions (i.e., with an open circuit on the secondary side), mainly caused by the magnetization process of the core material, including hysteresis loss and eddy current loss.

1. Hysteresis loss

Principle: Under the influence of an alternating magnetic field, the iron core is repeatedly magnetized (the direction of the magnetic domains constantly changes), and the friction and collision between molecules generate heat. Hysteresis loss is closely related to the hysteresis characteristics of the material, the alternating frequency of the magnetic field and the magnetic flux density.

Influencing factors: The smaller the hysteresis loop area of the material, the lower the loss. Silicon steel sheets are widely used due to their low hysteresis characteristics. By reducing the carbon content of silicon steel sheets and optimizing the grain orientation (such as oriented silicon steel sheets), hysteresis losses can be further reduced.

Optimization direction: Use high-permeability and low-hysteresis materials (such as amorphous alloys), or improve the microstructure of materials through heat treatment.

2. Eddy current loss

Principle: An alternating magnetic field induces closed eddy currents in the iron core. According to Joule's law (P=I² rp =I²R)

P=I2

R), eddy currents generate heat on the core resistance. Eddy current loss is directly proportional to frequency, core thickness (sheet thickness), and the electrical conductivity of the material.

Influencing factors: The greater the thickness of the core, the longer the eddy current path and the higher the loss. Materials with high electrical conductivity have more significant eddy currents.

Optimization direction: Adopt a laminated structure of thin silicon steel sheets (with a thickness typically ranging from 0.23 to 0.5mm), and apply insulating layers between the sheets to block the eddy current path. Suppress eddy currents by using high resistivity materials (such as amorphous alloys).

Ii. Copper Loss (Load Loss

Copper loss is the loss generated by the resistance of the winding and the current through the winding, also known as load loss.

● Principle: When current passes through the winding, due to the resistance of the wire (RR

The existence of R) is based on Joule's law (P=I² rp =I²R

P=I2

R), electrical energy is converted into thermal energy. Copper loss is proportional to the square of the current and increases significantly with the increase of load.

● Influencing factors: The resistance of the wire is affected by the resistivity of the material (copper is superior to aluminum), the cross-sectional area of the wire, the length of the winding and the temperature. Under high load, the current increases and the copper loss rises sharply.

● Optimization direction: Increase the cross-sectional area of the wire to reduce resistance; Use materials with low resistivity (such as copper conductors); Optimize the winding structure (such as helical or foil windings) to shorten the conductor length; Strengthen the heat dissipation design (such as adding heat sinks and oil cooling systems).

Iii. Minor Losses

In addition to iron loss and copper loss, transformers also have other losses that cannot be ignored, collectively referred to as secondary losses, mainly including:

1. Magnetic flux leakage loss

The leakage magnetic flux does not completely pass through the main magnetic circuit but passes through the structural components of the transformer (such as clamps and oil tanks), inducing eddy currents and generating heat.

Optimization measures: Optimize the winding arrangement and magnetic shielding structure, use low magnetic resistance materials to guide the leakage flux, or adopt a magnetic split design.

2. Stray loss

It is composed of eddy currents and hysteresis losses generated by the leakage magnetic field in metal components (such as bolts and oil tank walls).

Optimization measures: Use non-magnetic materials (such as stainless steel instead of ordinary steel) to manufacture structural components, or cut grooves in structural components to separate the eddy current path.

3. Dielectric loss:

The polarization loss of insulating materials under alternating electric fields is particularly significant in high-frequency applications.

Optimization measures: Select insulating materials with low dielectric constant and low loss Angle (such as high-quality oil-paper insulation).

4. No-load current loss

When a transformer is no-load, the loss generated by the excitation current on the winding resistance, although the value is relatively small, still cannot be ignored during long-term operation.

Optimization measures: Reduce the excitation current by optimizing the core structure (such as reducing the air gap in the magnetic circuit).

Iv. Comprehensive Optimization Strategy

1. Material innovation: The use of amorphous alloy cores instead of traditional silicon steel sheets can significantly reduce iron loss (by 60% to 80%). Develop new types of transformers using high-temperature superconducting materials to eliminate copper loss.

2. Structural Design: Fine magnetic circuit design to reduce magnetic leakage; Optimize the winding arrangement and shorten the current path; The loss distribution was simulated by applying finite element analysis (FEM).

3. Heat dissipation technology: Forced cooling systems (air cooling, oil cooling, water cooling) or phase change material (PCM) thermal management to enhance heat dissipation efficiency.

4. Intelligent monitoring: Real-time monitoring of parameters such as temperature and current through Internet of Things sensors, and dynamic adjustment of load to avoid overload operation.

V. Practical Applications and Challenges

● High-efficiency transformers: For instance, the SH15 amorphous alloy transformer has a no-load loss that is over 70% lower than that of traditional transformers, making it suitable for energy-saving renovations in distribution networks.

● Challenges and Balance: Reducing losses requires an increase in material or manufacturing costs, and a trade-off must be made between efficiency and economy. For instance, amorphous alloys are relatively expensive, but their long-term energy-saving benefits can offset the initial investment.

Summary

The energy loss of a transformer is the result of the coupling of multiple factors such as material properties, electromagnetic design, and operating conditions. Iron loss is closely related to the magnetic properties of materials, while copper loss depends on current and resistance. Minor losses need to be suppressed through refined structural design. Through new materials, optimized design, intelligent control and comprehensive energy efficiency management, the efficiency of transformers can be significantly enhanced, contributing to the green and low-carbon development of the power system.