串聯諧振時,XL = XC,感抗與容抗扺消, 阻抗最小,電流最大
XL / XC = 160/40 = 4 ,電感抗與電容抗相差 4 倍
√4 = 2 ,所以 XL 縮小 2 倍 ; XC 放大 2 倍 時,XL = XC
∵ XL 要縮小 2 倍 所以 頻率 要縮小 2 倍(電感抗與頻率成正比)
∴ f0 = f/2 = 240/2 = 120Hz
電流 i(t) 與電源電壓 v(t) 同相位 ⟹ 諧振
ω = 1/√LC = 1/2
電感與電容扺消 Z = 5Ω
i(t)=100√2 sin(ω t-45°) / 5 = 20√2 sin(ω t-45°)
i(4π)=20√2 sin( 12 × 4π-45°) = 20√2 sin(-45°) = 20√2 × -1√2 = -20 A
電壓電流同相位,表示諧振,電容阻抗與電感阻抗相同互消
ωL = 1ωC
ωL ωC=1
ω2LC=1
電壓電流同相位,所以電感阻抗 XL = 電容阻抗 XC
R = V/I = 100√2 ÷ 10√2 = 10
XL = 5000 × 0.01m = 0.05Ω
XC = XL = 0.05 = 15000 × C
C = 15000 × 0.05 = 4000μF
f0=f√Xc / XL
= 60 √10 / 0.4
= 60 × √25
= 60 × 5 =300Hz
諧振 ⟹ XL = XC
2000×5m = 12000×CP
CP = 12000×2000×5m
= 120000
= 50μF
XL = 5m×2000 = 10Ω
諧振時,總電流 = 電阻的電流
es(t) = 5√2 × 40 = 100√2 V
iL(t) = 100√210
=10√2 A
BW = 12πRC
250π = 12π×200×C
C = π2π×200×250 = 10μF
Q = R √C/L = 200 √10μ/1m = 20
BW = f0Q
f0 = BW × Q = 250π × 20 = 5000π ≑ 1592 Hz
下截止頻率 f1 = f0 - BW2 = 5000π - 125π = 4875π ≑ 1552 Hz
上截止頻率 f2 = f0 + BW2 = 5000π + 125π = 5125π ≑ 1632 Hz
RLC並聯諧振:
諧振時總電流最小
BW=f0 /Q ,BW 與 Q 成反比,諧振時器質因數愈大,頻帶寬度愈窄
諧振時總導納最小
功率因數為 1,電路諧振
V = 50V
消耗的平均功率為 25W ⟹ R = 50225 = 100Ω
ω = 1;XC = 1ωC = 110m = 100Ω
Q = RXC0 = 100/100 = 1