Three-Phase Distribution Transformers

In the transformer market, one of the most high-demand products is the three-phase distribution transformer. Due to their scarcity, a lot of consumers tend to go for cheap ones from low-quality manufacturers, which is definitely something you should not do.

This is why, DAELIM, one of the top companies in the world that specializes in three-phase distribution transformers, will provide and share with you their expertise of 15 years for you to be knowledgeable of three-phase distribution transformers.

DAELIM’s professional advice is to get the best-quality three-phase distribution transformer for safety purposes, lesser maintenance, longevity, and overall get the best value out of your money or your company’s money.

Three Phase Distribution Transformers: The Ultimate FAQ Guide

What are the uses of distribution transformer?

Three Phase Distribution transformer
Three Phase Distribution transformer

To begin with, you should get to know more about distribution transformers first since the three-phase distribution transformer belongs in this category or classification.

For starters, distribution transformers are also known as service transformers, but in this article, we will use the term “distribution transformer”.

Distribution transformers are primarily used for final voltage transformation purposes in the electric power distribution system. This steps down the voltage for compatible consumer use. This refers to houses and other buildings.

AC power distribution has been made feasible due to the development of the very first transformers back in the early 1880s.
Distribution transformers can also be mounted on a wooden pole, metal pole, or utility pole in general. These are specifically called pole-mounted transformers. They serve the same function and purpose, but their setting is above-ground.

Normally, distribution transformers have ratings that are less than 200 kVA (Kilovolt-ampere). But there are distribution transformers out there that have a much higher rating for further versatility and control.

In terms of energization, distribution transformers are typically energized the whole day, even if they do not carry any load. The purpose of this it reduces iron losses, which is one of their essential functions.

However, distribution transformers are also known to not operate at full loads, this is because their design was built to be efficient at lower loads only. This means that to utilize its efficiency, voltage regulation should be kept at a minimum only.


This type of transformer usually has a magnetic core that is composed of laminations of sheet silicon steel or also known as transformer steel. These are stacked and glued together with resin, steel straps, etc. The primary and secondary winding is also wrapped together with this.

There are different types of core construction or formations for distribution transformers, but all of them have one thing in common, which is their capability of reducing core losses. This also promotes good health to the transformer’s utility grids.

three-phase transformer winding
three-phase transformer winding

When it comes to core losses, these usually occur because of two reasons, it could either be due to eddy currents or hysteresis losses on the steel. If the transformer makes use of silicon steel, you can expect that it has a low hysteresis loss.

The laminated design prevents eddy currents from passing in the core, this dissipates power to the resistance of the transformer’s steel.

This is also one of the contributors to the high efficiency of distribution transformers (90%-99%).

When it comes to the manufacturing of a lot of transformers that are in a standard design, the setting of this will usually lead to C-shaped cores. This is because it is much easier to manufacture and economic as well.

Primary coils are usually wounds from enamel. It could either be copper or aluminum, the high current, low voltage secondaries are wounds that are using a thick ribbon of any of the aforementioned materials.

In terms of the resin-impregnated paper, these are used to insulate the windings. The entire assembly will be baked to cure the resin, and later on, submerge it into a powder-coated steel tank that is filled with transformer oil or mineral oil.

pad mounted transformer production plant

Transformer oil is responsible for cooling down the windings, and this protects the transformer from overheating and moisture attacks. Moisture attacks refer to bits of water floating on the surface of the transformer oil.

Usually, the tank is empty during manufacturing, this is to remove moisture in the tank. Moisture can cause arcing, which is definitely something you should avoid.

However, not all distribution transformers are suitable for indoor placements. Distribution transformers that are suitable for indoors are usually filled PCB liquid or polychlorinated biphenyl.

This chemical is not safe for the public, even animals can have adverse effects from this chemical. PCB is a highly discouraged chemical in the transformer industry and is mostly banned in a lot of countries.

4 Methods of Transformer Drying Treatment

Nowadays, there are fire-resistant liquids that are used for liquid-filled transformers. These are used to place make indoor transformer settings possible without posing any threat to the people around its surroundings.

Alternatives such as vegetable oils have been experimented with as well, but so far, no other type of oil can replace the effectiveness of transformer oil.

Depending on the manufacturer, some manufacturers include accessories such as surge arrestors or protective fuse-links for safety purposes. Some transformers have these components mounted as well, but they are separately mounted outside the tank.


Pole transformers and pad-mount transformers are basically the same when it comes to converting high voltages of the above-ground or underground distribution lines to lower voltages inside buildings.

Primary distribution lines make us of the three-phase system. This is why the main distribution lines consist of three worse and a neutral. However, the neutral is only optional. When it comes to the North Americal System, you would usually encounter single-phase transformers connecting to only one phase wire.

The primary is responsible for providing power to standard distribution voltages. The ratings of this can range from 2.2 kV to 35 kV, but this depends on the local distribution practice, as well as the distribution standards.


Distribution transformers including three-phase distribution transformers can usually be found at power plants and service drops. You would see lines or wires connected to a utility pole or underground lines to houses and other buildings.

three-phase distribution transformers are commonly used in supplying power to buildings outside the vicinity, and even at long distances.

One of the applications of the power supply is the overhead wire of railways that is supported with alternating current or better known as AC. In this certain situation, single-phase transformers are more suitable for this.

You would be surprised to know that a lot of houses can be powered by one distribution transformer, although it varies, even low rating distribution transformers can supply power of up to 50 houses.

For rural distributions, it may require one transformer per consumer but this heavily depends on how much electricity the consumer needs.

Similar to large commercial buildings, even a single building would need multiple distribution transformers. Urban areas could usually have their primary distribution lines underground. These transformers are usually locked in metal enclosures for safety purposes from outside elements that could possibly disturb the operation of the transformer.

A lot of buildings have electric services provided at primary distribution voltages, and these building usually have their own transformers. Their purpose is usually for stepping down voltages (decreasing).

Aside from urban and rural areas, distribution transformers can also be commonly found in collector networks. The best examples of this are wind farms. Their main function in collector networks is to increase or step-up power for each utility to connect to a substation that is very far away.

Single-Phase Transformer vs Three-Phase Transformer

DAELIM has included this section for you to determine and know what are the similarities, differences, and unique features of the two.

Single-phase distribution transformers or single-phase power systems are used with the help of power lines. There is only one winding for each; one primary winding and one secondary winding.

These are required to achieve voltage transformation. Single-phase transformers make use of these windings to transform the voltage, and they come in different variants as well, that have different functions, power, mounting agents, taps, kVA rating, and many more.

33 KVA class distribution transformer

These are commonly labeled as 240 or 480 VAC primary and 120 or 240 VAC secondary. Three-phase distribution transformers simply overpower single-phase distribution transformers. However, there are suitable applications for each transformer.

There might be cases that single-phase transformers are more appropriate, not three-phase distribution transformers, or vice versa.

For three-phase distribution transformers, the generated power will then be sent out to three different lines, this is why it is called “three-phase power.”

Connection Mode of Working Winding of Three-phase Transformer

However, for three-phase distribution transformers to work, you must have at least three winding or coils that are connected to the right order to match or connect with the right incoming voltage.

Afterward, it then transforms the new voltage to the right or appropriate voltage level that is needed.

The supply ability of single-transformers is quite limited compared to the capability of three-phase transformers.

Supply Ability

200 Set/Sets per Month 10KVA / 15KVA / 25KVA / 37.5KVA oil-immersed single phase transformer

Packaging Details

In terms of its packaging, it does have the upper hand since it is lighter.

  • Packaging Details: International Packing Method according to client’s requirement.
  • 25kva 37.5kva 50kva single phase pole mounted distribution transformer 75kva 250kva,100kva high voltage single phase transformer

DAELIM Three-Phase Distribution Transformers

Below are DAELIM’s best-selling three-phase distribution transformers. If you have any questions or concerns, do not hesitate to contact DAELIM’s team of professionals for immediate accommodation.

10KV Class Three Phase Oil-Immersed Distribution Transformer

10KV Class Three Phase Oil-Immersed Distribution Transformer

The DAELIM 10KV Oil-Immersed distribution transformer is considered to be one of the most important electrical devices in the distribution network and power supply. Moreover, they are commonly used in industrial and mining applications since they can fit into small spaces.

Aside from that, unlike other transformers – it is less noisy with a strong overload capacity. It has two variants as well, namely; hermetically sealed-type and conservator type.

This transformer can be commonly found in power plants, mining sites, laboratories, agriculture applications, and many more.

Supply Ability

  • 800 Set/Sets per Month Competitive

Packaging Details

  • International Wooden Case

Competitive price oil-immersed 2500kva amorph transformer 6 kV.

20KV Class Three Phase Oil-Immersed Distribution Transformer

20KV Class Three Phase Distribution Transformer
20KV Class Three Phase Distribution Transformer

Aside from its higher kilovolt-ampere rating, the DAELIM 20KV Three-Phase Oil-Immersed Distribution Transformer has more advantages as well,

These are the following advantages it has to offer:

  • More power supply capabilities.
  • Enhanced voltage quality
  • Mitigate energy losses in the power system
  • Fewer construction fees
  • Can be used for energy conservation in the power system

Supply Ability

  • 300 Set/Sets per Month 

Packaging Details

  • Wooden case or according to customer’s requirements

20kv 600kva copper core distribution power transformer price

35V Class Three Phase Oil-Immersed Distribution Transformer

35V Class Three Phase Oil-Immersed Distribution Transformer
35V Class Three Phase Oil-Immersed Distribution Transformer

For the highest rated transformer in DAELIM, the 35kV Three-Phase Oil-Immersed Distribution Transformer comply with standards of the ANSI C57. 12.00, GB1097, GB/T6451, and IEC60076.

These transformers offer no-load loss and on-load losses which is great so that you won’t be having to face those issues as you are operating the transformer.

Its core has a good-quality C.R.G.O. core type with high-quality and oxygen-free copper coil, safe operation, minimal design, and is popularly used. This transformer also follows the standards of the IEC IEEE.

Its oil tank is sheet type or expansion, and it does not necessarily need an oil conservator. Its height is also less – for less air contact. This prolongs the longevity and sustainability of the transformer.

Supply Ability

  • 200 Set/Sets per Month 

Packaging Details

  • International Standard Wooden Case.

Distribution transformers 1000kva power transformer 35kv oil immersed transformer 5000kva power distribution

Final Thoughts on Three-phase Distribution Transformers

Three-phase distribution transformers are generally outstanding. For starters, they are much better than single-phase distribution transformers in large projects or uses. For small projects, you don’t have to worry about smaller and less efficient transformers as well because there are smaller versions with fewer kVA ratings of three-phase distribution transformers.

Overall, these are excellent electrical devices that do great in what they are made to do. As mentioned, if you have any questions or concerns, you may contact DAELIM for fast accommodation.

Custom Three-Phase Distribution Transformer

When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.

We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.

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