neutral current calculation

[chan0828]

Hi,

I have a difficulty of this calculation.

In 208V 3ph-4w system,

A-N has a coil with an impedance of 8 ohms and a power factor of 0.9 lag

C-N has a heater load of 10 ohms

Calculate the neutral current.

Can anybody help me?

 

[charlie b]

We like to help those who help themselves. Can you tell us what you have tried, and what (if any) results or problems you have so far?

Welcome to the forum.

 

[nakulak]

For what class is this the homework ?

 

[Cold Fusion]

...In 208V 3ph-4w system,

A-N has a coil with an impedance of 8 ohms and a power factor of 0.9 lag

C-N has a heater load of 10 ohms

Calculate the neutral current. ...

Since you are doing this type of problems, I suspect you already know most of this.

So here's a start: (Definition: Symbol "<" means "phase angle")

It's a vector problem.
Ia +Ib + Ic + In = 0

Ic = 0 <0 so,
Ia + Ib = -In

let Va = 120V <0
and Vb = 120V <120
and Vc = 120V <-120

Za = 8 < (acos(.9)) = 8<25.84 degrees
Ia = Va/Za = 15 <-25.84

If the math makes sense to you, you likely have a plan for the rest.

If not, then we need to attack this another way.

cf