Invented by Galileo Ferraris, Mikhail Dolivo-Dobrovolsky, Jonas Wenström and Nikola Tesla in the late 1880s, the three phase system is less popular as compared to the single phase but, is actually more economical. This is because it uses less conductor material to transmit electrical power. Let us learn more about the three-phase system and three-phase transformers.

What is three-phase?

In three-phase, as the name suggests, three conductors carry alternating current of same frequency and voltage amplitude relative to a common reference but, with a phase difference of one-third the period. This common reference is connected to the ground and a current carrying conductor known as the ‘neutral’. The phase difference results in the voltage of a conductor reaching its peak at 1/3rd of a cycle after another conductor and 1/3rd of a cycle before the third conductor. The delay brings in constant transfer of power, which produces a rotating magnetic field in an electric motor.

How do single phase and three phase differ?

In single phase circuits, there is only one phase, meaning that the current will flow through only one wire and there will be only one return path to complete the circuit. Thus, minimum amount of power can be transported in single phase. This has been a very old system used since ages. However, with the invention of three-phase where more than one phase can be used for generating and transmitting current, things have changed. In the polyphase system, three phases are sent together from the generator to the load, where each phase has a difference of 120° angle electrically. This is how three phases are equally divided to cover a complete 360°.

A single-phase AC power supply uses two conductors – a phase and a neutral. When this is compared with a three-phase supply with no neutral and the same phase-to-ground voltage and current, the three-phase will be able to transmit three times as much power as single-phase while using only 1.5 times as many wires (3 wires instead of 2). A three-phase system may also use a fourth wire in low-voltage distribution known as the neutral. This neutral allows three separate single-phase supplies to be provided at constant voltage.

What makes three phase systems more desired?

Three-phase supplies have certain properties that make them advantageous and desired in power distribution systems.
  • Power transfer is constant, which helps in reducing generator and motor vibrations.
  • A rotating magnetic field is produced in a specific direction and with constant magnitude which simplifies the design of electric motors.
  • The phase currents tend to cancel one another, summing to zero, making it possible to reduce the size of the neutral as it carries little or no current.
  • The conductor needed in a three phase is 75% that of conductor required in single phase. Moreover, the instantaneous power in single phase falls to zero, while in three-phase, the net power from all phases provides continuous power to the load.

You may have now understood that three phase transformers have higher efficiency and minimum losses as compared to single phase. If you are looking to buy these transformers, you can get in touch with Miracle Electronics who provides efficient and fault-free transformers set at high standards in accordance with international standards for power generation, transmission and distribution.

For any query please click  OR mail at