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

M

#### myself

Jan 1, 1970
0
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!

P

#### Paul Hovnanian P.E.

Jan 1, 1970
0
myself said:
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!

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

M

#### mansour

Jan 1, 1970
0
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
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

myself said:
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!

M

#### mansour

Jan 1, 1970
0
myself said:
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!

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

M
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