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Home > Home & Garden > Electrical & Lighting   »   2-phase vs 3-phase degrees of seperation

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Old Aug 24, 2006, 09:08 PM
malibuclassic77
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2-phase vs 3-phase degrees of seperation

At work we have 3-phase power. I understand the oscillations are 120 degrees apart.

At home I have 2-phase power. Are the oscillations 180 degrees apart? I understand the neutral on a 240v circuit should carry 0 as the phases cancel each other out.

My real question is that if we have a 2-phase motor powered by 2 phases of the 3-phase circuit at work, is the neutral again carrying 0 or would it carry some current because the 2 used phases are not 180 degrees of each other?

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Old Aug 25, 2006, 08:01 AM   #2  
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If the system is well balanced the neutral will carry little current. This is the way the power company likes it, but rarely the case. Any unbalance will cause a netural wire current flow.
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Old Aug 25, 2006, 08:25 AM   #3  
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You have single phase at home, it is called an Edison three wire system. Two hot legs are the one phase, the neutral is the center tap of the transformer, which divides the voltage in half.

If a 3 wire circuit is balanced there will be no current flow in the neutral.


A Single phase circuit off of a three phase with a neutral is always current carrying, never gets balanced.

You need all three hots with a neutral and each circuits to carrying the same load to see zero amps in a balanced three phase circuit.

The rotation is 360 deg on a true single phase service. A three phase is 120 deg apart.
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Old Aug 30, 2007, 11:14 AM   #4  
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Quote:
Originally Posted by malibuclassic77
At work we have 3-phase power. I understand the oscillations are 120 degrees apart.

At home I have 2-phase power. Are the oscillations 180 degrees apart? I understand the neutral on a 240v circuit should carry 0 as the phases cancel each other out.

My real question is that if we have a 2-phase motor powered by 2 phases of the 3-phase circuit at work, is the neutral again carrying 0 or would it carry some current because the 2 used phases are not 180 degrees of each other?
NO CURRENT in nutral is not 0,the phasor sum of current in 2 phase is not 0...........
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