1. Lecture 101 EEE 302 Electrical Networks II Dr. Keith E. Holbert Summer 2001

2. Lecture 102 Source/Load Connections The equivalent load may be in an equivalent delta (  ) or wye (Y) configuration –the delta load configuration has no neutral line –the current is zero in the neutral line for a balanced wye load configuration Source/Load connections can be connected in any of the possible combinations: Y source -Y load  source -Y load Y source -  load  source -  load –Analysis prefers the first connection (Y-Y)

3. Lecture 103 Balanced Wye-Wye Connection ZYZY ZYZY ZYZY Load V an +–+– +–+– V bn +–+– V cn n c b a

4. Lecture 104 Balanced Wye-Wye Connection The line-to-line voltages (or line voltages) are V ab = V P  3  30° V bc = V ab  -120° V ca = V ab  -240° where V P is the magnitude of the phasor voltage between any two lines The magnitude of the line voltage is V L = V P  3

5. Lecture 105 Balanced Wye-Wye Connection The line current for phase a is I a = V an / Z Y = V p  0° / Z Y –In a Y-Y connection the magnitude of the line current (I L ) equals the magnitude of the load current (I Y ) The neutral current I n is I n = I a + I b + I c = 0 Balanced Y-Y three-phase ac circuits may be analyzed on a per phase basis

6. Lecture 106 Balanced Wye-Delta Connection ZZ ZZ ZZ a c b Load V an +–+– V bn V cn n +–+– +–+–

7. Lecture 107 Summarizing A very good summary appears on pages 568-9 of the textbook including a figure and table for explanation

8. Lecture 108 Class Examples Extension Exercise E10.1 Extension Exercise E10.2

9. Lecture 109 Three-Phase Power Relationships The real and reactive power per phase are The total real, reactive, and complex powers are

10. Lecture 1010 Class Examples Extension Exercise E10.8 Extension Exercise E10.10