Transformers can be classified into several types based on different criteria, such as cooling medium, core structure, purpose, and winding configuration. Here are the common types:
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By Cooling Medium:
- Oil-Immersed Transformer: This is a widely used type. The transformer core and windings are immersed in insulating oil. The oil not only provides insulation but also helps dissipate heat generated during the operation of the transformer. It has good heat dissipation performance and can handle relatively high power. However, there is a risk of oil leakage and fire, and it requires regular maintenance and inspection of the oil level and quality.
- Dry-Type Transformer: The core and windings of this type of transformer are made of solid insulating materials such as epoxy resin. It does not use oil as a cooling and insulating medium, so it is more environmentally friendly and has a lower risk of fire and leakage. Dry-type transformers are suitable for use in places with high fire protection requirements, such as indoor buildings, shopping malls, and hospitals.
- Gas-Insulated Transformer: The insulation and cooling of this transformer are achieved by using a gas such as sulfur hexafluoride (SF6). It has excellent insulation performance and a small footprint. Gas-insulated transformers are often used in special environments such as substations in urban areas or areas with limited space.
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By Core Structure:
- Core-Type Transformer: The core of this transformer is in the shape of a closed magnetic circuit, with the windings wound around the core. The magnetic flux is concentrated in the core, resulting in high magnetic efficiency. Core-type transformers are widely used in power transmission and distribution systems.
- Shell-Type Transformer: The windings surround the core in a shell-like structure. This design makes the transformer more suitable for high-current applications and has better mechanical strength. However, its magnetic efficiency is slightly lower than that of the core-type transformer.
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By Purpose:
- Power Transformer: It is used to transmit and transform electrical energy in power systems. Power transformers are usually large in size and have high power ratings. They are the key equipment in power transmission and distribution systems, responsible for stepping up or stepping down the voltage to meet the needs of different electrical equipment.
- Distribution Transformer: It is used to distribute electrical energy to end users in the power distribution network. Distribution transformers are generally smaller in size and have relatively lower power ratings compared to power transformers. They are installed in residential areas, commercial buildings, and industrial plants to provide power for various electrical appliances.
- Special-Purpose Transformer: These transformers are designed for specific applications, such as rectifier transformers used in rectifier circuits, furnace transformers used in industrial furnaces, and isolation transformers used for electrical isolation and safety purposes.
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By Winding Configuration:
- Two-Winding Transformer: It has a high-voltage winding and a low-voltage winding, which are used to transform the voltage between two different voltage levels. This is the most common type of transformer.
- Three-Winding Transformer: In addition to a high-voltage winding and a low-voltage winding, it also has a medium-voltage winding. Three-winding transformers can be used to connect three different voltage levels in the power system, providing more flexibility in power transmission and distribution.
- Autotransformer: The primary and secondary windings of an autotransformer have a part of the winding in common. This design can save materials and reduce costs compared to a two-winding transformer. Autotransformers are often used in situations where the voltage transformation ratio is relatively small.