The Versatility of Three-Phase Transformers


Three-phase transformers are used for generating, transmitting, and distributing electrical power. A 3-phase transformer has three different voltages, and the currents differ in phase-time.

A three-phase transformer is made by joining three single-phase transformers and forming a three-phase transformer bank. Or a pre-assembled three-phase transformer with three pairs of single-phase windings on a single laminated core can be used. Three-phase is generally used in power circulation, it is obvious to see the reason why three-phase transformers are used to step voltage down or up. Though, regular single-phase transformers can be used in a group just as well; using a three-phase transformer is just easier.

Here are a few differences between step-up and step-down three-phase transformers:

Step-up Transformer

This type of transformer increases the transmission voltage which helps reduce power shortages. An increase in voltage decreases the line current and power loss from cable resistance. Not to mention reducing the pressure on conductors. Generally, electricity is generated at 11kV and transmitted at 22 kV, or 44 kV and higher voltage levels.

This is where a step-up transformer comes into the picture. These transformers are used to increase the voltage at these levels. They are also used to start electric motors because the high voltage helps initiate motor rotation and overcome the starting resistance.

Since the value of the primary current is high, the transformers have primary windings of thick, insulated copper. Another thing that influences the voltage of a 3-phase transformer is the type of winding configuration used. This is used when calculating the turns ratio of a three-phase transformer so that the desired value of step-up voltage is achieved.

Step-down Transformer

The voltage at the end of transmission needs to be reduced since the power consumption occurs at a lower voltage. Most electrical voltages work at 240V, so the kV range needs to be reduced, and a step-down transformer is used for this. The principal of these transformers is the same as a step-up transformer, but their effect is the opposite.

They transform a high-voltage, low-current power in the primary to high-current, low-voltage power in the secondary. Thick copper windings in the secondary coils are used for the high secondary currents due to the stepped-down voltage.


This connection is generally used for three-phase loads but can have a single-phase component.

These transformers can be used for both single- and three-phase loads. The load should be distributed equally between each of the three phases.

The Three-phase transformers

These transformers are used in most of the electrical transmissions and distributions. They are also used in industries using three-phased equipment. The benefits of these type of transformers include:

  • They provide electrical isolation between the two parts of a circuit.
  • They provide improved safety since there is isolation between the circuit.
  • The power is delivered at a better rate than three single-phase transformers.

This makes three-phase transformers an important part of all modern electrical equipments, and if you’re looking to install such a transformer, Electpower is the best place to do so. Electpower is the three-phase transformer manufacturer, providing high quality and custom designs.