Here is a list of 23 Transformers categories. It encompasses a wide range including high voltage isolation transformers, high voltage transformers, audio transformers, power transformers, etc. You can search for an overview, principle, and usage of each category, as well as find manufacturers and distributors.

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What Is a Transformer?

A transformer is a static induction device that uses electromagnetic induction to convert an alternating voltage or current to a desired value.

Generally, a transformer that steps down voltage is known simply as a transformer, while a transformer that steps up a voltage is called a step-up transformer.

Transformers consist of an iron core and windings. They have two windings wound around a ring-shaped iron core. The winding connected to the power supply is called the primary winding, and the winding connected to the load side is called the secondary winding. The characteristic of a transformer is that it generates heat when in use due to iron loss and winding resistance, so energy is consumed by heat and output is reduced.

Transformers with a capacity of 50 kVA or less are defined as small capacity, those with a capacity of 500 kVA or less are defined as medium capacity, and those with a capacity of over 500 kVA are defined as large capacity, but the range is vague and undefined. They can also be referred to as low voltage, high voltage, ultra high voltage, extra high voltage, etc., depending on the voltage used.

Types of Transformers

There are various types of transformers, classified by structure, refrigerant, and cooling method.

Classification by Structure

  • Internal Iron Type Transformer: This type has the iron core inside the windings and is widely used because it is easy to manufacture and maintain and is resistant to mechanical stress.
  • Outer Iron Transformers: These transformers have the iron core on the outside of the windings and are difficult to manufacture and maintain. The outer iron type is mainly used for low-voltage and high-current applications.

2. Classification by Cooling Medium

  • Oil-Filled Transformers: Insulation is achieved by enclosing mineral oil or synthetic insulating oil in a tank, which cools and insulates at the same time.
  • Dry-Type Transformers: These transformers use air or gas (SF6: sulfur hexafluoride gas) as a refrigerant and are often used in small transformers.

3. Classification by Cooling Method

There are three types of refrigerant cooling methods for both oil-filled and dry-type transformers.

  • Self-Cooling Type: Cooling is done by natural convection of the refrigerant.
  • Water-Cooled: Cooling water is circulated to dissipate heat.
  • Wind-Cooling Method: This method cools by forcibly blowing air through a fan.

In addition to the above, the classification can be made in detail according to the number of phases, insulation method, heat resistance class, etc., but the three main types are listed above. Although transformers are sometimes classified according to their intended use, the structure of transformers is the same only that the designation changes depending on the place of use and how the transformer is used.

Principle of Transformers

When an AC voltage is applied to the primary winding of a transformer, a magnetic flux is generated in the iron core, and when the generated flux passes through the iron core and crosses the secondary winding, an induced electromotive force is generated.

When the primary voltage (V1), secondary voltage (V2), number of primary windings (n1), and number of secondary windings (n2) are used, the relationship V1/V2 = n1/n2 is established. The output voltage is proportional to the turn ratio, and any desired voltage can be obtained by changing the primary voltage or the number of windings (e.g., tap switching).

The Ranking of Companies in the Transformers Sector

*This ranking is solely among the companies registered with Metoree, sorted by the number of employees. Please use this as a rough guide to understand their scale.

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