# Determining the Current on the Neutral in a 3 Phase, 4 wire system with both resistive & reactive circuits.

Could anyone tell me how you would determine the current (amps) on the neutral in a 3 Phase, 4 wire system, with both resistive & reactive circuits of varying
voltages (208 & 120). If there is a formula for figuring this out, I would appreciate the knowledge. Thank you!
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myself wrote:

Tnere isn't a simple formula. It involves adding complex (A + jB) numbers.
First of all, loads connected across two lines (208V single phase) will produce no neutral currents. Same holds true for three phase, three wire loads.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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The Vector sum of the current in three phase in any given moment is equal to neutral current, this is independent from the connection & the type of the neutral. It is clear if forth wire does not exist or if you have balance three phase load the sum will be zero. IA+IB+IC=In in practice in order to calculate the neutral current you need to know the angle between the phases you can choose one of the phases as reference with angle zero & the other two can be measured or expressed in respect to "A" phase & if this is known it will be only vector summation.
rgds mansour

neutral in a

voltages (208 & 120).

knowledge. Thank you!
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neutral in a

voltages (208 & 120).

knowledge. Thank you!
Vector sum of three phase current in any given moment is representing the neutral current this is independent of neutral type,load type or network connection, if the load is balanced or if the forth wire dose not exist this sum is zero. Please note this is vector sum & you should determine the angle of each current in respect to each other.
In=IA+IB+IC
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