三相四线电能表无功功率表达式( ):
A.P=UAIACosφA+UBIBCosφB+UCICCosφC;
B.P=UAIAsinφA+UBIBsinφB+UCICsinφC
C.P=UAIACtgφA+UBIBCtgφB+UCICCtgφC
D.P=3UICtgφA
正确答案是B