Introduction of three phase transformer

three phase transformer (1)

In power plants and substations, the transformers are used to transfer voltages. Transformers input multiple windings can input different voltage, meanwhile, multiple windings can also used for output voltage. For three phase transformer, it has three windings, and be connected with different connection (such as: star, delta).

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Table of Content

What is a three phase transformer?

A three phase transformer is a combination of three single-phase transformers of the same capacity.

It has three core legs, each of which is wound around two coils of the same phase, one is a high-voltage coil and the other is a low-voltage coil. Three-phase electricity is generated. A generator with equal amplitude, equal frequency, and phase difference of 120* potential is called a three-phase generator; using a three-phase generator as a power source is called a three-phase power source; a circuit powered by a three-phase power source is called a three-phase circuit .

What are the types of 3 phase transformers?

There are several common types of three-phase transformers: three-phase dry-type transformers, three-phase isolation transformers,Three-phase control transformer, three-phase autotransformer. Below we explain these categories.


Three-phase dry-type transformers

Three phase dry type transformers  called cast resin transformers, they are widely used in industrial and mining , post and telecommunications,Textiles, railways, construction sites, schools, hospitals, hotels, national defense, scientific research and other departments ,Electronic computers, precision machine tools, computed tomography (CT), precision instruments, real AC stabilized power supply for inspection devices, elevators, imported equipment and production lines also suitable.

It is used for low-voltage power distribution with low power supply voltage and large fluctuation range.

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Three-phase isolation transformer

Three-phase isolation transformer is widely used in industrial and mining enterprises, power plants, airports, high-rise buildings, subways and other places with high safety and fire protection requirements, for voltage conversion, lighting electrical facilities, power supply, rectifier power supply. It is mainly used in power systems and industrial and mining enterprises where the power load is required to be electrically isolated from the power grid.

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Three-phase control transformer

Three-phase control transformer is widely used in various three-phase power supply occasions with AC 50-60HZ, input and output voltage not exceeding 1000V. It is very suitable for three-phase power transformers in low-voltage switchgear and electrical transmission control equipment. Different input and output voltages, connect types, taps, distribution of winding capacity, secondary single The configuration of the phase winding, the use of the rectifier circuit, whether it is required to have a casing, etc.,

The transformers will able to designed and manufactured according to customer’s requirements.

Three-phase autotransformer

The three-phase autotransformer has no primary and secondary windings,

The input and output use the same winding coil, and the tap change of the coil is used to achieve the voltage regulation.

It is a transformer without isolation between input and output, generally used for voltage regulation

[such as a voltage regulator for refrigerators], or other purposes such as single-phase motor speed regulation, but work in

Circuits and equipment under safe voltage are not allowed to use such transformers.

What is the difference between single phase and three phase transformer?

Different definitions

Single-phase transformer transformer, with the electromagnetic induction principle , it can transfer AC voltage. For single phase transformer, it consists of input coil, output coil , iron core made of silicon steel sheet. In electric field, it is generally used for voltage rise and fall, impedance matching, safety isolation, etc.

Three-phase transformer:

One three phase transformer can be seen as combination of 3 sets of single phase transformers of the same capacity. Generally it is three core-legged, sometimes 4 or 5 legged. In the leg it is wound around 2 coils of the same phase, they are HV winding and LV winding.

Different applications

Single phase transformer are frequently used in in low voltage distribution networks , and it’s load is small.

Three-phase transformer: Three phase transformer is widely used AC circuit and the frequency is 50Hz or 60H, in many industries such as precision machine tools, mechanical and electronic equipment, medical equipment, rectifiers, lighting, etc.

Different characteristics

Single phase transformer has simple structure, the voltage, capacity is smaller, and volume is small.Compare with 3 phase transformer, it has lower iron loss.

A three-phase transformer can contain the neutral grounding, which can alleviate the common mode interference of the power grid. The three-phase four-wire system of the three-phase transformer changes the delta connection to the star connection.

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What is Star and Delta Connection in transformer?

Three phase transformer connections, we are going to explain the three phase transformer delta wye connection.

The star connection is a connection method in which the three ends of the three-phase load are connected together as a common terminal, and three live wires are drawn from the three head ends. Angular connection is a connection method in which the beginning and end of each phase of the three-phase load are connected in sequence.

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What happens if one phase of a 3 phase transformer fails?

three phase transformer (2)

One three-phase transformer has A, B, and C three phase to supply power. Under normal circumstances, the three-phase current should be the same size, so as to achieve the ideal operating state of three-phase balance. Therefore, it is easy to damage the transformer when the transformer is in phase loss operation or the three phases are unbalanced. When a phase of a three-phase transformer is out of phase, the phase-opening current is minimum or even 0, which will cause the current of the other two phases to suddenly increase, the temperature of the transformer coil and iron core will increase, and abnormal noise will occur during operation. even burn out. 

When poor contact occurs, the contact surface of the wire is poor, which causes the contact area at the joint to become smaller, and the overcurrent capacity decreases, and its resistance value is larger than the original. It is equivalent to connecting a large resistor in series on the circuit, which has energy loss. If the current is large to a certain extent, it will heat up.

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What is three phase transformer working principle?

The working principle of the transformer is the principle of electromagnetic induction.

Customized three phase transformers

Daelim is a transformer manufacturer that can fully comply with IEEE, IEC, AS, ANSI, DOE, CSA and other international standards. The professional technical team can customize various three-phase transformers. If you encounter three-phase transformer problems that cannot be solved, you can contact the Daelim team.

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About Bin Dong

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.