§9-3电感、电容的功率 必电感功率 设电感两端电压：u(t)=Umcos(wt) Um_Um∠0°_Um ∠-90° ,joL oL∠90°oL Z i(t)= m cos-0-S n(ot) p(t)=u(t)i(t)=UI cos(@t)si(ot) 2Un1n2 cosfwf）)sin() 2 =UI sin((2ot)→电感平均功率P=0（吸收/释放) 10§9-3电感、电容的功率 ❖ 电感功率 ❖设电感两端电压：u(t)=Umcos(ωt) 10 = −      = = = • • • 90 90 0 L U L U j L U Z U m m m m L m I    ( ) cos( 90 ) sin( t) L U t L U i t m m     = −  = sin( 2 ) 2cos( )sin( ) 2 1 ( ) ( ) ( ) cos( )sin( ) UI t U I t t p t u t i t U I t t m m m m      = = = = 电感平均功率P=0（吸收/释放）