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Basic Guide to Different Transformer Types

Different Transformer Types

How much do you know about the types of transformers? Different types of transformers have different structural principles, which are mainly reflected in different types of connections, windings, electrical, oil, protection, and their application and so on. Next, let’s learn more about different types of transformers through the following articles.

Daelim is a professional transformer manufacture more than 15 years in China.Daelim aims to provide customers with the highest quality products and services. At the same time, this is our value and advantage. Every time we innovate our products, deliver to our customers, and communicate with our partners’ long-term customers, we demonstrate our unique strengths. Our products comply with CSA/ANSI/IEEE and other standards, and have a number of ISO certificates. To provide you with high-quality products and services.

Pad-mounted Transformer

We can provide you single phase and three phase pad mounted transformer

Dry-type Transformer

Type:Cast resin; Rated Capacity: Up to 25MVA; Rated Voltage: Up to 36KV;

Pole Transformer

TypeCSP type Frequency: 50/60Hz; Rated Power: 5~167kva

Oil immersed transformer

Frequency: 50/60Hz Rated voltage:10kv, 20kv,30kv Rated Power: 400~2500kva

Table of Content

What are the 5 applications of transformer?

1.Industrial and agricultural production

Power transformers are widely used in industrial and agricultural production. It is mainly used as a transformer used in power transmission and distribution systems. This type of transformer has formed a series and has been mass-produced. Transformers from 10kva to 630kva are generally called I, I type products, from 800kva to 6300kva is type II, from 8000kva to 63000kva is type III, and above 63000kva For Class IV, all kinds of transformers can be composed of various specifications of voltage combinations according to each voltage and temperature.

2.Industrial electricity and lighting electricity

According to different uses, it can be divided into step-up transformer and step-down transformer, among which the step-down transformer with low voltage of 400V is called distribution transformer. The highest voltage from the generator is 15.75KV, of which 6.3KV and 10.5KV are the most. It is impossible to transmit such a low voltage to areas hundreds of kilometers away. In order to transmit the electric energy from the power station, the voltage must be increased to 38.5KV through the transformer. 121KV, 242KV, and 363kV are sent out. After the high-voltage electricity reaches the power supply area, it has to go through a primary substation (voltage drop is 38.5KV or “35KV) and a secondary substation (voltage drop is 6.3KV or 10.5KV), and then the electricity is directly sent to The user area is stepped down through a nearby distribution transformer to supply power for factories and lighting.

3.Industrial refining

The metal materials and chemical raw materials used in industry are all refined with electric furnaces, and the power supply of electric furnaces is supplied by electric furnace transformers. The characteristics of electric furnace transformers are that the secondary voltage is very low (usually tens of V). To hundreds of V), but the current is very large, a maximum of tens of thousands of amperes, the voltage of our electric furnace transformer is 10KV or 35KV, and the individual is 110KV.

4.DC power supply

Smelters: many electrical equipment requires DC power supply, such as trams, electric locomotives, rolling mills in factories, smelters and electrolysis of chemical plants. Converting AC into DC requires a rectifier, and the power transformer used for the energy current is called a rectifier transformer. The difference between the rectifier transformer and the electric furnace transformer is that the secondary coil is connected into six or twelve phases to improve the rectification efficiency.


Mine transformers are specially used for underground power transformation in mines. They are called mine transformers. They are made of casings to prevent ore from breaking and a moisture-proof sealed structure. The other is a transformer that runs into the face of the tunnel. , known as explosion-proof transformer, this transformer is dry type, and the mechanical strength of the casing is high, so as to prevent gas explosion.

Different types of distribution transformer

he types of distribution transformers produced by Daelim usually include: three-phase pad-mounted transformers, single-phase pad-mounted transformers, cast resin transformers, single-phase pole-mounted transformers and skid-mounted substation transformers. The design and production of these types of transformers can meet international standards such as IEEE/ANSI, IEC, CSA, DOE, AS, etc. Therefore, if you need a quotation or technical data sheet for these types of transformers, you can contact the Daelim team.

Different types of transformer connections

There are many types of connections for transformers. The latest representation of transformer winding connection groups is specified in the IEC standard. That is, three-phase transformer windings, when connected into star, triangle, and zigzag shapes, are respectively represented by Y, D, and Z for high-voltage windings; for medium and low-voltage windings, they are represented by lowercase letters y, d, and z, respectively. If it is a star-shaped or zigzag-shaped connection with a neutral point, it is represented by YN or ZN, yn or zn respectively. The transformers are combined in the order in which the high-voltage and low-voltage windings are connected to form the connection group of the windings.

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Common three connection groups and use occasions

1. The meaning of Dyn11: D: high-voltage side delta connection, y: low-voltage side star connection; n: low-voltage side neutral point lead; 11: high and low voltage phase difference 30 degrees.

Occasion: The single-phase unbalanced current exceeds 25% of the rated current, that is, there are many single-phase loads; the system has large harmonics and has a harmonic elimination effect;

2. The meaning of Yyn0: Y: high-voltage side star connection, no neutral point lead; y: low-voltage side star connection; n: neutral point lead; 0: high and low pressure difference 0 degrees.

Occasion: The three-phase load is basically balanced; the harmonics of the power supply system are not serious; it is often used in 10KV systems.

3. Yd1 meaning: Y: high-voltage side star connection; d: low-voltage side delta connection; 1: high and low voltage phase difference of 30 degrees.

Application: 35KV power distribution system.

Keep on reading The Ultimate Guide to 300 kVA Pad Mounted Transformer

Different types of transformer windings

1. Double-winding transformer: There are two windings, which can only convert the power supply voltage into one voltage level, or there are two voltage levels of AC voltage involved in the transformation and mutual connection, single-phase transformers and three-phase transformers have this kind of form.

2. Three-winding transformer: There are three windings, which can convert the power supply voltage into two voltage levels, or the AC voltage with three voltage levels participates in the transformation and mutual connection.

3. Self-coupling transformer: There is only one winding, which is used to connect power systems of different voltages, and can also be used as an ordinary step-up or step-down transformer.

4. Split transformer: a multi-winding power transformer in which each phase consists of a high-voltage winding and two or more low-voltage windings with the same voltage and capacity. There are two kinds of axial split and radial split, which are used for factory transformers and start-up transformers.

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What is a three phase transformer and feature?

When we use a transformer, if we want to input different voltages, we can use multiple different windings to adapt to different input voltages.

Moreover, the purpose of outputting different voltages can also be achieved by using multiple windings.

Three separate windings can be connected in different ways to allow the transformer to input three-phase alternating current, and the output is the same.

This is a three-phase transformer. Its structural feature is that the three-phase magnetic flux has its own separate magnetic circuit, which is not related to each other.

The characteristic of the three-phase core transformer is that the iron cores of three single-phase transformers are combined into one, and the three-phase magnetic circuits are related to each other. The main magnetic flux of any phase must have the other two-phase magnetic circuits as its own closed magnetic circuit. . When a three-phase symmetrical voltage is applied on one side, the three-phase main magnetic flux is symmetrical, and no magnetic flux passes through the middle iron core column, so the middle iron core column can be omitted. For the convenience of manufacture and cost reduction, the core legs can be placed on the same plane. Obtain the core structure of the three-phase core transformer.

What is the transformer oil?

Transformer oil is a mineral based oil that is commonly used in transformers for its chemical properties and dielectric strength. This oil in your transformer acts as an insulator and a cooling agent. Over time, the oil will degrade resulting in the potential for faults and costly repairs.Therefore, transformer oil needs to be regularly filtered or even replaced.

What is the function of transformer oil ?

Tap changer of pad mounted transformer function is increase or decrease the output secondary voltage by changing the turn ratio of primary or secondary winding. This is installed in high voltage side.
Off – circuit tap changer and dual voltage selector switches, when specified, shall be externally operable lever – handle types, made of corrosion – resistant material. The means for operating the pad mounted transformer tap changer shall be installed in the cable entrance compartment. The highest voltage tap shall be tap position 1.

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1. Insulation

Insulation materials are very strong in air and can improve air permeability.

2. Confrontation

Spreading oil is larger than heat, often spreading grease. Proximity to the iron and spread of grease makes the aid of the oil produced when the heat is spread. When the tarpaulin is heated, the effect of oil is produced, and the effect of convection oil, which scatters wavelengths through a wide-flowing flow, spreads widely.

3. Arc suppression function

On different switches and display panels, there are paints that the contacts can display. Since the adjustable oil paint is shown on this app, the tactile is well dispersed on the current effect, and the performance is shown, showing the various pressures, showing that with such arc performance, it is easy for us to achieve.

How often to change transformer oil and what to pay attention to?

Transformer oil is recommended to be replaced every 6 months.And we should be noticed in use:

1. When the transformer oil is not enough to be added, the new transformer oil that meets the new oil addition standard and has not been used should be preferred. At the same time, the same oil base, brand, and type of additive should be added. The characteristic index of the supplementary oil should not be lower than the characteristic index of the oil in the equipment. When the amount of new oil added is less than 5%, there is generally no problem, but if the amount of new oil added is relatively large, oil chromatography analysis and pressure test should be performed before adding oil to confirm that there is no oily sludge Precipitation, and when the acid value and dielectric loss coefficient are smaller than those in the equipment, oil supplementation can be carried out.

2. Under normal circumstances, oils with different oil bases cannot be mixed. Under special circumstances, if it is necessary to mix different grades of new oil products, it is necessary to judge whether the oil meets the local standard through the actually measured freezing point of the mixed oil, and finally carry out the mixed oil experiment. The results of the mixed oil sample test for the acute test should be no worse than the worst single oil sample. If the running oil is mixed with new or old oil of different grades. In addition to measuring the freezing point of the mixed oil in advance, aging tests and sludge tests should also be carried out to observe the sedimentation of sludge. It can be used only after there is no precipitation. The mixed oil sample should give better results than the original running oil. can be mixed.

Different of dry-type transformmer and oil-immersed transformer.

Many people on the dry transformer and oil-immersed transformer, easy to confuse, can not tell the difference between the two. Today violet electric gentleman answers the difference between the two in detail for you.

In terms of price, dry is more expensive than oil. Volumetric, large – volume oil changes more than dry oil.In the complex building (basement, floor, roof, etc.) and crowded places need to use dry transformer. Oil transformer is used in an independent substation. Box transformer is generally dry transformer. Outdoor temporary electricity generally adopts oil transformer. During construction, dry and oil transformer are selected according to the space. Oil transformer can be selected when the space is large, and dry transformer can be selected when the space is crowded.

Regional climate is humid and sultry areas, easy to use oil change. If dry transformer is used, it must be equipped with forced air cooling equipment.


Packaging form is different, dry type transformer can directly see the core and coil, and oil-immersed transformer can only see the transformer shell.

2. Different lead forms

Different dry type transformers mostly use silicone rubber bushing, and oil-immersed transformers mostly use porcelain bushing.

3. Different capacity and voltage

Dry type transformer is generally applicable to power distribution, capacity under 1600kva, voltage under the 10Kv, also have individual do 35Kv voltage class, and the oil-immersed transformer is can be raised to achieve full capacity, voltage class did all voltage, 1000Kv test lines under construction in China, must be used oil transformer.

4.Insulation and heat dissipation are not the same

Dry type transformer is generally insulated with resin, by natural air cooling, large capacity by fan cooling, and oil transformer by insulating oil insulation, insulation oil in the transformer internal circulation generated by the coil to the transformer radiator for heat dissipation

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Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.