(. 3.21). , .
. 3.21 : IA IB, UAC UBC.
. 3.21
, , . 3.21, . , ,
(3.43)
p = uA iA + uB iB + uC iC.
(3.44)
iA + iB + iC = 0.
(3.45)
iC = -(iA + iB).
iC ,
(3.46)
p = uA iA + uB iB - uC (iA + iB) = (uA - uC) iA + (uB - uC) iB = uAC iA + uBC iB.
u i , ()
(3.47)
,
(3.48)
P = UAC IA cos(UAC^IA) + UBC IB cos(UBC^IB) = P1 + P2.
UAC, UBC, IA IB , .
, .
IA = IB = I, UAC = UBC = U.
. 3.22
(. 3.22) , α UAC IA α = φ - 30, β UBC IB β = φ + 30.
(3.49)
P1 = U I cos(φ - 30),
(3.50)
P2 = U I cos(φ + 30).
(3.51)
P1 + P2 = U I [cos(φ - 30) + cos(φ + 30)] = U I cos φ.
, , , , , .
1 2 φ = 0. φ > 60, 2 .
, . , . .