PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Alternating Current Analysis 263

R.3.80 The system voltages, as well as the loads in a 3 Φ system can be connected in either

a ∆ or a Y confi guration, as illustrated in Figures 3.43 through 3.46, where E 1 + E 2 +

E 3 = 0.

R.3.81 A balance system consists of a system where the load impedances are Z 1 = Z 2 = Z 3

in a Y confi guration, or when Z 4 = Z 5 = Z 6 in a ∆ confi guration; refer to Figures 3.42

through 3.46.

R.3.82 Standard circuit techniques such as loop or node equations can be used to analyze

polyphase systems (to determine currents or voltages).

R.3.83 When a 3 Φ system is connected to an unbalanced Y load, the neutral nodal point

referred by N is not at the neutral potential, and is labeled with an O. The change

in voltage between the balanced and the unbalanced case is referred as VON, and is

referred to as the neutral displacement voltage.

FIGURE 3.42

3 Φ system with sequence ABC.

C

VAC

B

A

N

(N = Neutral

point)

VAB

VAB = V ∠ 120 °

VBC = V ∠ 0 °

VAN = D ∠ 90 °

VBN = D ∠− 30 °

VCN = D ∠− 150 °

VCA = V ∠ 240 °

D = V

3

FIGURE 3.43

3 Φ–Y system connected to a Y load.

Z 2

E 3 E 1 Z 1 Z 3

E 2