three phase transformer

Three phase transformer is still our common transformer type, usually there are two series of three phase autotransformer and three-phase isolation transformer. If you want to buy a three-phase transformer then this guide is for you.

1. What is a three phase transformer?

As known, a single phase transformer is a device that is capable of transferring electrical energy from one circuit to one or more circuits based on the concept of mutual induction. It comprises two coils – a primary and a secondary coil, which helps to transform the energy. The primary coil is connected to a single phase supply, while the secondary is connected to a load.

Similarly, a three-phase transformer consists of three primary coils and three secondary coils and is represented as 3-phase or 3ɸ. A three-phase system can be constructed using three individual identical single-phase transformers, and such a 3 phase transformer is known as the bank of three transformers. On the other hand, the three-phase transformer can be built on a single core. The windings of a transformer can be connected in either delta or wye configurations. The working of the 3-phase system is similar to a single-phase transformer, and they are normally employed in power generation plants.

2. Types of three-phase transformer

Three-phase transformers are divided into three-phase autotransformers, three-phase isolation transformers, three-phase rectifier transformers, Scott transformers, three-phase high-frequency transformers, three-phase power transformers, etc.

3. What is a three-phase auto transformer

A normal transformer will have two windings which are physically separated but magnetically coupled together with the help of a magnetic core. As they are separately been isolated, they are called as primary winding which receives the voltage from the source and secondary winding which transfers to the output load.

But the transformer in which there will be only one winding which is common to both primary and secondary is called Autotransformer. The term Auto here refers to that the voltage input variations will be automatically can be improved or can be reduced utilizing the single winding.

4. What is a three-phase isolation transformer？

The principle of three-phase isolation transformer basically adopts the principle of electromagnetic induction. It is safe to use a three-phase isolation transformer, which is generally used as a maintenance power supply. The isolation transformer is commonly 1:1 transformer, but it has different specifications. Three-phase isolation transformers are used for changing voltage, lighting, power supply and rectifying power supply, widely applied to industrial and mining enterprises, power plants, airports, high-rise buildings, subways and other places with high fire safety requirements.

5. How a three phase transformer works

The primary winding of the three phase transformer is energized from a three phase supply. Then, the flux is produced in the core by the primary currents in the three windings. The core has three limbs, where any two limbs act as return path for the flux in the third limb. The flux produced by the primary windings induces emf in the secondary windings depending on the transformation ratio of the 3-phase transformer.

In case of a three phase transformer, the transformation ratio is defined as the ratio of the secondary phase voltage to the primary phase voltage and is denoted by K.

three Phase Isolation Transformer Schematic Diagram

6. What is the purpose of a three-phase transformer?

Three-phase transformers are used to step up or step down high voltages at various stages of the transmission system.

Three-phase transformers are commonly used to power homes, businesses, and industrial sites. Larger domestic sites, most commercial sites, and industries have many 3-phase motors that require 3-phase power. Three-phase motors are more efficient than single-phase motors, so they can be used anywhere a larger motor is required.

The use of three-phase transformers in machines is also very common.

7. How to connect a three-phase transformer

A three-phase transformer consists of three transformers, which are either separate or combined with a single core. The primary and secondary of the transformer can be independently connected in star or delta. There are four possible ways of connecting a three-phase transformer bank.

• Δ – Δ (Delta – Delta) connection
• Υ – Υ (star-star) connection
• Δ – Υ (Delta – Star) connection
• Υ – Δ (Star – Delta ) connection

The choice of connection for a three-phase transformer depends on various factors, such as the availability of neutral connection for earth protection or load connection, insulation and voltage stress to earth, availability of third harmonic flow paths, etc.

8. Advantages of three-phase transformers

• Inexpensive: Three-phase transformers are cheaper compared to single-phase transformers. Compared with three single-phase transformers, it is less expensive.
• Lightweight: Three-phase transformers are lighter in weight and smaller than single-phase transformers, which means they take up less space.
• Assemble in the shortest time: very easy to assemble. We can get single-phase power from a three-phase transformer, but not vice versa.
• Higher Efficiency: Three-phase transformers perform their functions more efficiently and provide more power than single-phase transformers.
• Easier installation: The pre-wired three-phase transformer is ready to install, making installation very easy and smooth.
• Easy to transport: In order to provide the same output, the material used to make the core of one three-phase transformer is very less than that of three single-phase transformers. Therefore, they are not only easy to transport, but also less expensive to transport.

9. Disadvantages of three-phase transformers

• Standby equipment costs more: The individual cost of redundant equipment is high and it is difficult to repair or correct any problems. In a three-phase transformer, all three units share a common core. Therefore, if the unit fails or is damaged, the entire three-phase transformer must be shut down.
• Repair Costs: Three-phase transformers are expensive to repair because of the high cost of replacing each component. Therefore, in terms of service restoration, backup unit costs are higher compared to single-phase transformers.
• Reduced capacity: Since the three-phase transformer is self-cooling, the power of the transformer is also reduced at the same time.
• Fault Correction: If any phase of a three-phase transformer fails, the fault is transferred to the other two phases. Therefore, the entire unit needs to be replaced.

10. Three-phase transformer main components

There are three basic parts of a transformer:

• an iron core which serves as a magnetic conductor,
• a primary winding or coil of wire and
  a secondary
• winding or coil of wire.

11. How to buy a three-phase transformer that fits me？

First of all, please determine the following requirements of your transformer, and only after determining your own needs can you choose a transformer that suits you. If you don’t have the transformer you need, you can also contact the transformer manufacturer for customization. SHUOGONG can provide such a service.

• Load Voltage
• Load Current/Ampere
• Line Voltage

12. How do transformer manufacturers and suppliers choose?

We all know that there are many transformer manufacturers and suppliers in the world, so how should we choose?

First of all, you should consider the technical level of transformer manufacturers, whether they have strong research and development capabilities, and whether they can meet your needs, especially for some special voltages.

Secondly, you should consider the cost of your transformer, including the price of the transformer, the shipping cost of the transformer, etc.

In addition, you should also consider the after-sales service of the transformer. Although the probability of transformer problems is relatively low, we still have to take this problem into account. How about the after-sales capabilities of transformer manufacturers and suppliers? Can they provide services such as returns and exchanges. These are very important.

13. What is the price of a three-phase transformer?

The price of three-phase transformers is relatively wide. First of all, if you want to buy a three-phase transformer, you must first select the type of transformer, power and input and output voltage.

In this way, a correct transformer quotation can be obtained.

Below I have listed the market prices of some commonly used three-phase transformers. for reference only.

This price does not represent the price of SHUOGONG transformers, if you have a demand for our transformer prices, you can contact us for a quotation.