Part 3: Using Vectors to Approximate the Neutral Current in a Three Phase Power System

for three phase 60 hertz systems with unity power factor and resistive loads

by Gerald Newton
November 9, 1999

Using the tools from Part 1and Part 2 solve the following problems.

1. In the diagram below if the loads are electric heaters how much current would the neutral carry?

In a balanced three phase system supplying resistive loads the power factor is approximately 1 and the current in the neutral is 0 amperes.

2. In the diagram below if the C phase line current is 30 amperes what would the current be in the neutral if the loads are electric heaters?

Using the formula from the previous discussion.

|A| = 50 amperes, |B| = 50 amperes, |C| = 30 amperes and

3. Find the neutral current in the follwing.

4. Find the neutral current for the following:

	Click the mouse button to place several vectors on the screen. Then click on action to sum them up. The vector is the sum is the white vector from the origin to the head of the last vector.
	Use the mouse button to lay down up to ten vectors. Click on the Action button to sum the up.