# Fundamental In Electricity

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In a 3 phase supply, we say it is 440 V Ac. In a 1 phase supply we say it is 220 AC. When 1 phase is 220 , logically 3 phase is 660 . How come it is 440 V AC.
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In a 3 phase supply, we say it is 440 V Ac. In a 1 phase supply we say it is 220 AC. When 1 phase is 220 , logically 3 phase is 660 . How come it is 440 V AC.

Hiya

New to this site, but do belive that it is due to the waves of electricity. I finished my level 2 C&G 3208, 3 years ago, but didnt really learn that much as I was also do my level 2 in refrigeration.

If this is wrong, then I would be very interested in finding out why.

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• 3 weeks later...

dear brother

potential can be calculated between two phases or phase to neutral if we checked the potential between two phases we will find the result 440 volts and phse to neutral potential should be found 220v.

we never calculate the potential between three phases i think you question should be why?

we know that current need to complete a circuit a neutral or another phase or another word for made a clsoe circuit we need a neutral or phase or tow phases.if you convert 3 phase system into two phasess system then you same says 440v ac if you convert three phase system into 4 phase system then you same says 440 v ac. here 440ac the measurment of potential between two phases. not the some of phases.

God bless you

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• 5 months later...
In a 3 phase supply, we say it is 440 V Ac. In a 1 phase supply we say it is 220 AC. When 1 phase is 220 , logically 3 phase is 660 . How come it is 440 V AC.

Hello,

In star connection system, line voltage (measured between phase and phase, in this case 440V) = square root of 3x 1 phase voltage (measured between 1 phase and neutral).

In fact, 1 phase voltage in this case = 440/1.73 (square root of 3) = 254V AC.

You can not simply add 220 + 220 + 220 =660V, but you must use vector adding method.

Regards,

Hung

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