In-Depth Explanation of Transformer Knowledge: Structure, Principles, and Applications（2-1）

Transformers are indispensable electrical devices in power systems, widely used in power transmission and distribution, industrial control, and electronic equipment. They play a critical role in ensuring the safe and stable operation of electrical networks by transferring electrical energy through electromagnetic induction and converting voltage levels.

1. Basic Concepts of Transformers

1. Definition:
A transformer is a static electrical device that uses electromagnetic induction to convert alternating current (AC) from one voltage level to another while maintaining the same frequency.

2. Functional Characteristics:

• Voltage step-up or step-down conversion
• Electrical circuit isolation (e.g., isolation transformers)
• Providing matched voltages for various loads
• Reducing transmission losses in long-distance power delivery

2. Basic Structure of Transformers

A typical transformer consists of the following main components:

1. Core
   The core forms the magnetic path of the transformer, usually made of stacked silicon steel sheets with high magnetic permeability to reduce eddy current and hysteresis losses. Common shapes include E-core and C-core designs.

2. Windings
   Windings are the electrical circuits of the transformer, divided into primary windings (input side) and secondary windings (output side). Additional windings or taps may be included depending on the application.

3. Insulation Materials
   Insulation between windings and between windings and the core prevents short circuits or breakdowns. Common materials include paper, oil-impregnated fibers, and epoxy resins.

4. Cooling System
   Depending on the cooling method, transformers can be classified as dry-type (air-cooled) or oil-immersed (oil-cooled). Oil-immersed transformers offer better heat dissipation and are suitable for high-capacity applications.

5. Enclosure and Accessories
   The enclosure protects internal components from environmental factors. Accessories include oil level indicators, thermometers, breathers, and tap changers.

3. Working Principle of Transformers

Transformers operate based on Faraday's Law of Electromagnetic Induction:

When an AC voltage is applied to the primary winding, it generates an alternating magnetic field in the core. This changing magnetic field induces an electromotive force (EMF) in the secondary winding, enabling energy transfer from the primary to the secondary side.

The voltage transformation ratio follows this formula:

Where $U_1$ and $U_2$ are the primary and secondary voltages, and $N_1$ and $N_2$ are the number of turns in each winding. If $N_2>N_1$, it is a step-up transformer; if $N_2<N_1$, it is a step-down transformer.

4. Main Types of Transformers

1. By Phase Number:

   • Single-phase transformers
   • Three-phase transformers

2. By Cooling Method:

   • Dry-type transformers (air-cooled)
   • Oil-immersed transformers (oil-cooled)

3. By Function:

   • Step-up transformers
   • Step-down transformers
   • Isolation transformers
   • Auto-transformers

4. By Installation Type:

   • Pad-mounted transformers (prefabricated)
   • Pole-mounted transformers
   • Underground transformers