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General Science => General Science => Topic started by: highvoltpower on 22/04/2016 07:52:39

Title: Transformer 415-240V used in switchgear, is single phase ?
Post by: highvoltpower on 22/04/2016 07:52:39

Transformer 415/240V used in switchgear, is single phase or two ya three phase ?

Title: Re: Transformer 415-240V used in switchgear, is single phase ?
Post by: evan_au on 22/04/2016 11:49:40

In countries like UK and Australia, power is distributed to residential streets as a three-phase voltage, with 240V from each phase to neutral.

Small appliances are connected from phase to neutral, and operate from 240V AC.

However, if you have a high-powered motor, it is more efficient to power it from three-phase power. If you measure the voltage from phase-to-phase, it is 240V * √3 =415V AC*.

So your 415V transformer is a three-phase transformer.

*In more detail, you can represent 2 voltage phases as 2 sides of an isosceles triangle, with the phase-to-phase voltage being the third side. The angle between the sides is 120°. Applying the cosine rule (https://en.wikipedia.org/wiki/Law_of_cosines), the length of the third side is found to be 240√3 = 415.