C F O B B’ F + + + + A O A’ B’ B F + + + + A O A’ x O (Δ) x’ C M t M 0 P O A φ ωt α α O l T P F’ F t F s O P P’ (♠ ) O x’ x M P M 0 ωt φ A  A  O A 1 x’ A x A 2 3 π − 32 π (Δ) O A’ A 1 x A C F y O O (Δ) x’ A 1 A 2 ∆ x a ωt B n A B O I 0 x v 0 K A B N M D B 3 B 2 B 1 A 3 A 2 A 1 3 2 1 S N L A B 1 A  2 A  A  n ωt A B B M S R O P x 1 A  2 A  A  O x’ (♠ ) M 1 M M 2 P P 2 P’ P 1 φ φ 1 φ 2 x x’ (♠) A  2 A  1 A  (♠ ) O x x’ A  1 A  2 A  L A B M m N A A’ B B’ h d A B h M B l d 2 d 1 A i O 1/ 3 1/ 3 t A 1 Taûi 1 A 3 A 2 B 3 B 2 B 1 Taûi 3 Taûi 2 daây pha 1 Daây trung hoøa A 1 A 2 A 3 B 3 Daây pha 1 Taûi 1 B 1 B 2 Taûi 2 Taûi 3 V 1 V 2 V 3 R L C BA V 1 V 2 M R,L C B A A A V 1 V 2 M C R N A L R C L R C L 1 M B A L 2 , r A V R C BA L A ~ L K C –+ B E O T C’ L A L’ L C P L A L C A B B B M R,L C B A R L C B A M N E B E B A 2 A 1 A i t O 12 l h 3 2 1 B 2 B 3 B B 1 D R B A O i t A R D 4 B D 2 C D 3 D 1 D 2 a 1 B A b A B 1 2 A B R 3 R 2 R 1 A + + r q 1 q 2 F 2 F 1 + r q 1 q 2 F 2 F 1 - - + - + A C B F 2 E  + - E  E  D ' 1 E  ' 2 E  D E  2 E  1 E  C E  A B + - q 1 C q 2 A C + B E E E E + + A O A E A + + + B C A C A D A E B E C E D + (BC = d) + C V B > V C B q 0 . . + – V 3 O y x + + + – – – O ♠ A 1 A A 2 φ 1 φ 2 E 1 E E B C + + – E Ñieän moâi – – – + + + + + +– – – Q 1 C 1 + Q 3 1 Q 2 1 C 21 C 31 + + + – – – – AB E A + + E B E C E D E E 0 A C A C A C A B C 1 A C 21 C 31 C α – B + + – D H B d α d 2 d 1 (BC = d) + C V B > V C B q 0 . . V 3 O y + – – – – + + + x V 0 + + + – – – V = 0 B E C E 0 A α E Ñieän moâi – – – + + + + + +– – – S R K i i’ r I A H K i I’ JB i S O i gh I 0R U  0C U  x 0 U  0L U  φ A’ B A B’ O F F’ + + A’ B A B’ F F’ + O + A’ B A F F’ + B’ B C 1 C 21 C 31