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Oil-Immersed and Dry-Type Power Transformers: a Beginner's Guide
Release time: 2026-06-12 10:54:52

Common power transformers are mainly divided into dry-type transformers and oil-immersed transformers, which are also two types of transformers commonly used in the world at present;The specification and capacity of power transformer are the most important parameters in power system, and their selection is directly related to the stable operation and energy efficiency of power system.

Understanding the basic knowledge of these two common transformers can also help us better choose the transformer equipment suitable for the project.

In today's article, let's introduce it.Oil immersion typePower transformerAnd the basic knowledge of dry-type power transformers, I hope to help you.

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Specification and model of power transformer

The specification of power transformer is usually composed of several parts, including phase number, cooling mode, winding number, design serial number, rated capacity and voltage level. The following are some common specifications and their meanings:

Number of phases:

Three-phase(S): indicates that the transformer is a three-phase transformer.

Single phase(D): Indicates that the transformer is a single-phase transformer.

Cooling method:

Natural cooling(No specific marking): Natural cooling is adopted for some transformers.

Air Cooling(F): indicates that the transformer is cooled by air.

Oil-immersed self-cooling(O): indicates that the transformer is oil-immersed and naturally cooled.

Number of windings:

Double winding(No specific marking orS): Indicates that the transformer has two windings.

Three windings(Z): Indicates that the transformer has three windings.

Design No.:

They are usually represented by numbers or a combination of letters to distinguish different design versions of the transformer.

Rated capacity:

In kilovolt-amperes(kVA)Or megavolt-ampere(MVA)Is the unit indicating the rated power of the transformer.

Voltage class:

Indicates the rated voltage of the high voltage side and low voltage side of the transformer.

 

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Power transformerCapacity

The capacity of a power transformer is one of its most important parameters, usually measured in kilovolt-amperes.(kVA)Or megavolt-ampere(MVA)Is expressed as a unit. Common capacity specifications are:

Small transformers: such as10kVA20kVA50kVAAnd that like, and is suitable for supply power to a small pow distribution system or specific equipment.

Medium transformers: e.g.100kVA200kVA500kVA630kVA800kVA1000kVAWidely used in industrial, commercial and residential distribution systems.

Large transformers: such as1250kVA2000kVA3150kVA4000kVA5000kVAAnd tensMVAIt is often used in large-scale industrial projects, power grid construction and other fields.

 

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Oil immersion typePower transformerThe advantage of

Excellent thermal performance

The specific heat capacity of the insulating oil is high, the circulating cooling efficiency is superior to that of air, and the operating temperature can be effectively reduced.

Typical application: long-term full load or high temperature environment (such as tropical areas, steel plants).

Strong overload capacity

Short-time overload capacity up to rated load1.3~1.5Times (sustained2Hours), suitable for impact loads (such as motor starting).

Cost advantage

Lower initial procurement cost than dry-type transformers20%~30%Maintenance costs are also relatively low.

Excellent insulation performance

The oil-immersed environment can delay the aging of insulation, and the average service life can reach30~40Year (dry-type transformer approx.20~25Year).

Noise control

The oil medium cushions the vibration, and the noise level is usually lower than that of the dry-type transformer.5~10dB

 

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Dry type power transformerThe composition of

Iron core

Material: The core of dry-type transformer is usually made of high-quality silicon steel sheets, which are made by lamination and welding.

Winding

Material: The winding is covered with high quality electrical insulation material to ensure the insulation performance of the winding. High-strength enameled wire is often used for winding, which has good performance and heat dissipation.

Insulating material

Materials: The insulation materials of dry-type transformer are inorganic materials, such as glass fiber, epoxy resin, etc., to ensure the insulation performance and fire performance.

Enclosure

Material: The shell of the dry-type transformer is made of corrosion-resistant and fireproof materials, such as stainless steel, aluminum alloy, etc.

Cooling system

Type: The cooling system of dry-type transformer usually adopts natural cooling or forced air cooling.

Other attachments

Fastener and insulator: including clamp, screw, glass binding tape, steel binding tape, cushion block and clamp insulation, insulating tube and insulating pad, grounding lug and foot pad, etc.

 

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Power transformerThe choice

Oil-immersed type is preferred

Dry or amorphous alloys are recommended

Outdoor substation, wind power/Photovoltaic booster station

Indoor power distribution room and commercial complex

Industrial scenarios for long-term full load operation

Places with high fire protection requirements (hospitals, subways)

Stable ambient temperature (-20℃~40℃) area

High altitude area (to be used at reduced capacity)

Projects with limited budgets that can accept scheduled maintenance

Areas with extreme temperature differences (-40℃~50℃

 

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Sum up

Through the above article, we on the oil-immersedPower transformerAnd dry-type power transformers, as the global demand for electricity grows, power issues are becoming a problem for many large companies, especiallyAIImportant deployment of enterprises in related fields.

As the heart of power stability, transformer equipment plays an irreplaceable role.

We are one of the largest transformer manufacturers in China, providing high quality transformer production equipment for global customers, including winding machine, slitting machine, slitting line, welding machine, transportation platform, etc.

Enterprises are welcome to send inquiries, we will provide unparalleled service and more competitive prices.