Three-phase Transformers FAQs

Fig: Three-phase transformer working principle, photo collected from TAMESON site.

What is a three-phase transformer?

A three-phase transformer is made of three sets of primary and secondary windings, each set wound around one leg of an iron core assembly.

Working principle of three-phase transformer

Electrical Transformer Working Principle, 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.

Advantages of three-phase transformer 

The main advantages of the three-phase transformer over than single-phase transformer is as below:

• It is lighter and smaller. 
• It requires less space to install. 
• Low cost compared with three units of single-phase transformers. 
• Transportation is easy and also transportation cost is less.

Three-phase power supplies are more efficient. A three-phase power supply can transmit three times as much power as a single-phase power supply, while only needing one additional wire (that is, three wires instead of two).

3-types 3-phase transformer

Small power transformers, 

Medium Power transformers, and 

Large power transformers.

What is RYB in a transformer?

RYB simply stands for Red, yellow, and Blue respectively in a three-phase electrical system. In a three-phase electrical system, the three phases are separated by an angle of 120 degrees, and each phase is given a specific color.

The most common 3-phase transformer connections

The delta–wye connection is the most commonly used three-phase transformer connection. The wye-connected secondary allows a single-phase load to be distributed among the three phases to neutral instead of being placed all on one winding as with a four-wire delta secondary.

A combination of three-phase transformers is used

These four standard configurations are given: 

• Delta-Delta (Dd), 
• Star-Star (Yy), 
• Star-Delta (Yd), and 
• Delta-Star (Dy).

Three single-phase transformers may be connected together between their primary and secondary three-phase circuits.

Can it use more than a 3-phase transformer?

Yes, but not used normally, because the cost of the electrical system increases. The three-phase system delivers three times the power of a single phase. The 6 phase adds twice the power of the 3 phase. The drawback of more phases is that the transmission towers have to sustain more loads of conductors.

If you want more about transformer in detail may visit the article:

Transformer working principle and uses in the electrical engineering field.

1. Three-phase Transformer Connections;
2. Star/Star or Y/Y Connection;
3. Delta-Delta or ∆/∆ Connection;
4. Wye/Delta or Y/ Connection;
5. Delta/Wye or ∆/Y Connection;
6. Open-Delta or V-V Connection;
7. Three-phase to Two-Phase Conversion and vice-versa;