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Review of Linear Three-Phase AC Circuits EE 340 Y. Baghzouz

Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

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Page 1: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Review of Linear Three-Phase

AC Circuits

EE 340

Y. Baghzouz

Page 2: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Advantages of 3-Phase

Systems

Page 3: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Balanced 3-Phase Systems

Page 4: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

3-Phase Voltage Source

Page 5: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Neutral Wire Sharing

Page 6: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Neutral Current

Page 7: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Phase and Line Voltages

Page 8: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Example of Phase and

Line Voltages

Page 9: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Y-Connected Load

Page 10: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Δ-Connected Load

Page 11: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Power in Balanced 3-Phase Circuits

The real power, reactive power, apparent

power, complex power and power factor are

the same in each phase.

)cos(3)cos(3 IVIVP Lp

)sin(3)sin(3 IVIVQ Lp

Lp VIVS 33

Page 12: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Power measurement in 3-phase

4-wire circuit

If the load is balanced,

then P1 = P2 = P3,

hence, PT = 3P1

If the load is

unbalanced, P1≠P2≠P3,

hence, PT = P1+P2+P3

Page 13: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Power measurement in 3-phase

3-wire circuit: the 2-wattmeter method

Total power: PT = P1+P2

The load can be Y-

connected, Δ-connected,

balanced, or unbalanced.

Any one of the 3 phases

can be used as a

reference.

If the load is unbalanced,

then P1 ≠ P2

If the load is balanced,

then P1 = P2

Page 14: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Measuring active power in a high power circuit

Page 15: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Per-Phase Analysis in Balanced

3-Phase Circuits

Page 16: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Delta-Wye Transformation

Page 17: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Example of per-phase analysis

Find the complex power supplied by each of the

two sources.

Page 18: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Solution

Page 19: Review of Linear Three-Phase AC Circuits - egr.unlv.edueebag/Review of 3-Phase Ckts.pdf · Advantages of 3-Phase Systems . Balanced 3-Phase Systems . 3-Phase Voltage Source . Neutral

Example of 3-phase balanced circuit