Cast Resin Dry Type Transformer

Daelim Cast Resin Dry Type Transformer is in line with IEC726、GB/T10228-1997 standards.It has the characteristics of low loss, compact structure, light weight, low noise, moisture resistance, high mechanical strength, flame retardant, etc. , Strong overload capacity, low partial discharge quality. It is suitable for power transmission and distribution systems, especially for heavy load centers and places with special fire protection requirements.

35KV Class Three Phase Epoxy-resin Dry-type Transformer

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20KV Class Three Phase Epoxy-resin Dry-type Transformer

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10KV Class Three Phase Epoxy-resin Dry-type Transformer

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The Importance of Cast Resin Dry Type Transformer: The Ultimate FAQ Guide

Are you in need of a transformer that performs great in high moisture areas? Then the Cast Resin Dry Type Transformer (C.R.T) is the superior choice, and lucky for you, DAELIM has the best C.R.Ts. However, it is highly recommended that you understand first what you are purchasing.

This is why DAELIM prepared this guide for you to provide you detailed information, and of course, grant you the best purchase decision.

Concept of a Transformer

To better understand the transformer you are interested in, it is best to understand if it is the right one.


And to have that knowledge, learning the concepts by starting with the fundamentals is a good start.

Why do we need Transformers?

Transformers are the basic components for the transmission and distribution of electricity in a power system.

Why do we need Transformers in our Power System?

High power Transformer for Industry.

For normal use, a transformer is used to increase the voltage at the power generating station, also known as the step-up transformer. This is to minimize the transmission losses during the transmission of power.


In terms of decreasing the voltage in the distribution level, this is called step-down. The purpose of this is to supply power to the building.


Moreover, there are different appliances that are manufactured with different voltage requirements. In order for the appliance to operate, you need to adjust the voltage to a compatible level.


We can achieve that with the use of a transformer. For instance, specific appliances require specific voltages to run, and Transformers are used to adjust voltages to that specific requirement.

Why is it Called a Transformer?

Transformers are called transformers because of these very reasons,


But first, here’s a simpler explanation of how it works


So, what this does is that this device transfers electrical energy or the electrical power at different voltage levels and it transforms the voltage, and because of this process, that current in the windings also transforms.


This is why Transformers are called Transformers.

Mechanical Properties of a Transformer

Transformers are static devices, which means it has no moving parts in it.


It transfers the electrical energy from one part of the electronic circuit to another part without changing the frequency

Laminated Core

The purpose of a laminated core is to reduce eddy current and to maximize the permeability for the flux linkage in the secondary winding.


The core in the transformers is composed of laminated sheets of steel, with a little air gap in between them.


Windings are made up of copper or aluminum coated with very thin insulation which has a higher temperature and insulation class.


The conservator’s purpose is to store additional cooling oil that can be used or recycled after a short period of time.


The breather absorbs moisture content from the air which sucks in while the oil gets expanded or contracted.

Electronic Relay

The electronic relay or also known as the Buchholz relay secures the winding by protecting the winding from overheating.

History of Transformers

The first transformer was made back in 1885 by Ottó Bláthy but it was later on modified by William Stanley in the same year.


And not long after that, the following year, it was commercially used in the United States of America in 1886 with the design invented by William Stanley.



To make it not sound confusing, the transformer basically works on the principle of Electromagnetic Mutual Induction (E.M.I).

What is Electromagnetic Mutual Induction?

As there are two sets of winding, one is called the primary winding and the other one is called secondary winding.


When you energize the primary winding, a magnetic flux is created which is the same flux that links to the secondary winding.

Different Types of Transformers and its Uses

If you are wondering about the other types of transformers out there, here are the other variations below.

Core Type Transformer

The core type transformer has two limbs, and the windings are contracted on two limbs of the core material.

Shell Type Transformer

For the shell-type transformer, its core has three limbs and two windows. Both windings are contracted on the central limb specifically, one over the other.

Spiral Core Transformer

Lastly, the spiral core transformer has a similar construction to the wheels of spoke,

What are Cast Resin Dry Type Transformers?

So, what are Cast Resin Dry Type Transformers or C.R.T? C.R.Ts are transformers that are used in high moisture prone areas. They are designed specifically for this purpose and it does a very good job at it.


Its primary and secondary windings encapsulation are secure with epoxy resin. The function of this encapsulation is to prevent moisture from getting in that will drastically affect the windings.

What is a Dry Type Transformer?

A dry type transformer like the C.R.T is a classification or type of transformer that never uses any insulating liquid. Its windings and core are kept in a sealed tank that is supplied with a specific amount of pressurized air.

What are Dry Type Transformers For?

Tachnical Data for 35KV Class Three Phase Epoxy-resin Dry-type Transformer
Tachnical Data for 35KV Class Three Phase Epoxy-resin Dry-type Transformer

Three-phase Epoxy-resin Dry type Transformers are in conformity with standard of IEC726, GB6450, GB/T10228-1997, with features of low loss, compact and light weight, low noise level, damp-proof, high mechanical strength, flame resisting, strong overload ability and low partial discharge quality. They are applicable to power transmission and distribution system, especially to heavy load centers and places with special fire protection requirements.

Tachnical Data for 20KV Class Three Phase Epoxy-resin Dry-type Transformer
Tachnical Data for 20KV Class Three Phase Epoxy-resin Dry-type Transformer

Dry type transformers are the only transformers that perform well in high-moisture areas, and are commonly used for small to medium voltage applications. In terms of utility purposes, they are highly recommended.


The windings in dry transformers are made of copper or aluminum that are sealed in varnish. Yes, there are different variations for your preference.

Tachnical Data for 10KV Class Three Phase Epoxy-resin Dry-type Transformer
Tachnical Data for 10KV Class Three Phase Epoxy-resin Dry-type Transformer

Depending on your application and the environment of where you plan to place your transformer, DAELIM provides professional help to accommodate your concerns. When it comes to your personal preference, DAELIM offers different variants as well to attain your needs.

What is a Resin Transformer?

A resin transformer does not have insulating liquids immersed in the magnetic circuit and windings. Rather, they are cast with an epoxy resin mixture that is suited for commercial uses.

Are Cast Resin Dry Type Transformers Necessary?

Tachnical Data for Dry Type Distribution Transformer

There is no guaranteed safety if you use another type of transformer for high moisture-prone areas.


The C.R.T is specifically designed for that, which is why it is best to choose the safest option rather than a skeptical one.

Are all Transformers Dry Type?

Not all transformers are dry type, there are other types of transformers as well that serve with different functions. For dry type transformers like the C.R.T, these are power transformers with epoxy resin encased in their windings.


When it comes to the installation process, it is much easier since they do not require cooling oil.

What is a Cast Resin Current transformer?

With a lot of similarities in the definition above, Cast Resin Current Transformers or Epoxy Resin Cast Current Transformer is a dry type and its internal windings are coated with epoxy resin for its insulation.

This is common in instrument transformers wherein the primary function of it is to step down or decrease the high voltage and currents.

Where are Dry Type Transformers Commonly Used?

As aforementioned, they are commonly used in high moisture prone areas but they are also used in buildings and near buildings because dry type transformers are environmentally safe. However, they are flammable but not to the extreme level of other transformer types.


Dry transformers can be found in industrial buildings, factories, malls, hospitals, and other commercial areas.


Other Examples of where Dry Type Transformers are Used:

  • Residential
  • Complexes
  • Substations of Interior Cities
  • Large Apartments
  • Villages
  • Motels

The Difference between Dry Type Transformer vs Oil Type Transformer

Dry Type Distribution Transformer

An oil type transformer is a widely used type of transformer as well, but what are the major differences between the dry type transformer and oil type transformer?


And which one is right for you?


In this section, you will learn the differences between both transformers which can help you decide which type is suitable for you.

The Cooling Medium

The Dry type uses natural air or forced air to cool the core and internal windings. Whereas, the oil type transformer is dependent on mineral oil for cooling.

The disadvantage of using Mineral Oil


Mineral oil exposed to public areas is dangerous since it is highly flammable. It has been reported that almost 70%-80% of all transformer failures are due to internal winding failures which result in fire or explosion.

Advantage of using Air

It is perfectly safe for the public since its cooling medium is only air. This is one of the main reasons why consumers choose dry-type transformers over oil-typed transformers.


The dry-type transformer only requires little to almost no maintenance at all. There is no special maintenance needed for its condition to stay pristine. Compared to the oil-type transformer, it does require maintenance and it should be on a regular basis.


Sample oil is regularly taken on at interval to see whether or not it is contaminated. Furthermore, once the breather is installed in the transformer, it will require a replacement after a certain amount of time.



The dry type transformer has more noise than oil type transformers. The noise occurs because of Magnetostriction, due to this, the laminated cores are contracted or disturbed everytime air comes in contact with the magnetic field.


All the steel sheets vibrate which makes the noise. Also, there is also noise coming from the windings and load noise.


Therefore, the noise is more prominent on dry type transformers than of the oil type ones.

Advantages and Disadvantages

Of course, the C.R.T has its own advantages and disadvantages as well, and at this point these factors could also help you make the right purchase decision.


Below are the main or key advantages of using C.R.Ts.

Low Fire Hazard

As mentioned above, C.R.Ts are known to be less flammable compared to other types of transformers, and it is also self-extinguishing.

No Oil Usage

There is no oil usage in C.R.Ts which is why it also saves its users money because oil-typed transformers consume a lot of oil.


Environmentally Friendly

This is the reason why a lot of buildings and commercials use C.R.Ts because it keeps the people around the vicinity safe and secured.


Low-Cost Installation

You don’t have to worry about the cost of installation, especially if you are with DAELIM as DAELIM provides the best quality at a low price.

Low Maintenance

If you are looking for a transformer that requires little to almost no maintenance, then the C.R.T is best for your situation.


Aside from the fact that the C.R.T is moisture-resistant, it is also crack-resistant since it is made of bulky and tough materials which contributes a lot to its low maintenance attribute.


Here are drawbacks of the C.R.T that made some consumers reconsider their purchase.

Only Needs Air to Cool

So what does this have to do with being a disadvantage? Well, this makes liquid testing unneeded. You will need a technical personnel to clean and regularly check up on it.

Electric Breakdowns

There are electric breakdowns between the turns or parts of the windings which is a major issue because chances are, this leads to partial discharges before an electric breakdown.


Since the C.R.T is a dry type transformer, it has more noise than an oil type transformer. If that is a factor that bothers you, then you should reconsider different transformer options.


In conclusion, there is no better option out there when it comes to high moisture-prone areas, environmental security, and costing. The Cast Resin Dry Type Transformer is the only transformer that does exceptionally well in high moisture areas. You do not have to worry about spending money on oil as well since it does not require that.


However, do reconsider if you find the disadvantages a major issue. But for more questions and concerns, you can easily contact DAELIM’s contact support team for fast accommodation.

DAELIM: An Electric Product & Equipment Manufacturer.