目录
1. 三相电源
此处只介绍对称三相电源。
(1) 电压大小
电压瞬时表达式:
- u a = 2 U c o s ( ω t ) u_a = \sqrt{2}Ucos(\omega t ) ua=2Ucos(ωt)
- u b = 2 U c o s ( ω t − 120 ° ) u_b = \sqrt{2}Ucos(\omega t- 120°) ub=2Ucos(ωt−120°)
- u c = 2 U c o s ( ω t + 120 ° ) u_c = \sqrt{2}Ucos(\omega t + 120°) uc=2Ucos(ωt+120°)
电压相量形式:
- U ˙ A = U ∠ 0 ° \dot{U}_A = U∠0° U˙A=U∠0°
- U ˙ B = U ∠ − 120 ° \dot{U}_B = U∠-120° U˙B=U∠−120°
- U ˙ C = U ∠ 120 ° \dot{U}_C = U∠120° U˙C=U∠120°
特点:
u a + u b + u c = 0 u_a+u_b+u_c = 0 ua+ub+uc=0
U ˙ A + U ˙ B + U ˙ C = 0 \dot{U}_A+\dot{U}_B+\dot{U}_C = 0 U˙A+U˙B+U˙C=0
(2) 联结方式
① Y形联结
联结描述:各个电源的负端接在一起。
② 三角形联结
连接描述:各个电源依次首尾相连,组成一个闭环。
特点:
U ˙ A + U ˙ B + U ˙ C = 0 \dot{U}_A + \dot{U}_B + \dot{U}_C = 0 U˙A+U˙B+U˙C=0
I = 0 I = 0 I=0
没有中性点
2. 三相负载
(1) 联结方式
① Y形联结
若 Z A = Z B = Z C Z_{A} =Z_{B} =Z_{C} ZA=ZB=ZC,则为三相对称负载
② 三角形联结
若 Z A B = Z B C = Z C A Z_{AB} =Z_{BC} =Z_{CA} ZAB=ZBC=ZCA,则为三相对称负载
3. 三相输电线路
4. 三相电路的联结方式
(1) Y − △ Y-\triangle Y−△
线电压与相电压的关系:
U ˙ A B = 3 U ˙ A ∠ 30 ° U ˙ B C = 3 U ˙ B ∠ 30 ° U ˙ C A = 3 U ˙ C ∠ 30 ° } \left.\begin{matrix}\dot{U}_{AB} = \sqrt{3}\dot{U}_A∠30° \\\dot{U}_{BC} = \sqrt{3}\dot{U}_B∠30° \\\dot{U}_{CA} = \sqrt{3}\dot{U}_C∠30° \end{matrix}\right\} U˙AB=3U˙A∠30°U˙BC=3U˙B∠30°U˙CA=3U˙C∠30°⎭⎬⎫
线电流与相电流的关系:
I ˙ A = 3 I ˙ A ′ B ′ ∠ − 30 ° I ˙ B = 3 I ˙ B ′ C ′ ∠ − 30 ° I ˙ C = 3 I ˙ C ′ A ′ ∠ − 30 ° } \left.\begin{matrix}\dot{I}_{A} = \sqrt{3}\dot{I}_{A'B'}∠-30° \\\dot{I}_{B} = \sqrt{3}\dot{I}_{B'C'}∠-30° \\\dot{I}_{C} = \sqrt{3}\dot{I}_{C'A'}∠-30° \end{matrix}\right\} I˙A=3I˙A′B′∠−30°I˙B=3I˙B′C′∠−30°I˙C=3I˙C′A′∠−30°⎭⎬⎫
(2) Y − Y Y-Y Y−Y
线电压与相电压的关系:
U ˙ A B = 3 U ˙ A ∠ 30 ° U ˙ B C = 3 U ˙ B ∠ 30 ° U ˙ C A = 3 U ˙ C ∠ 30 ° } \left.\begin{matrix}\dot{U}_{AB} = \sqrt{3}\dot{U}_A∠30° \\\dot{U}_{BC} = \sqrt{3}\dot{U}_B∠30° \\\dot{U}_{CA} = \sqrt{3}\dot{U}_C∠30° \end{matrix}\right\} U˙AB=3U˙A∠30°U˙BC=3U˙B∠30°U˙CA=3U˙C∠30°⎭⎬⎫
线电流与相电流的关系
I ˙ A = I ˙ A ′ B ′ I ˙ B = I ˙ B ′ C ′ I ˙ C = I ˙ C ′ A ′ } \left.\begin{matrix}\dot{I}_{A} = \dot{I}_{A'B'} \\\dot{I}_{B} = \dot{I}_{B'C'} \\\dot{I}_{C} = \dot{I}_{C'A'} \end{matrix}\right\} I˙A=I˙A′B′I˙B=I˙B′C′I˙C=I˙C′A′⎭⎬⎫
(3) △ − △ \triangle-\triangle △−△
线电压与相电压的关系
U ˙ A B = U ˙ A U ˙ B C = U ˙ B U ˙ C A = U ˙ C } \left.\begin{matrix}\dot{U}_{AB} =\dot{U}_A \\\dot{U}_{BC} = \dot{U}_B \\\dot{U}_{CA} =\dot{U}_C \end{matrix}\right\} U˙AB=U˙AU˙BC=U˙BU˙CA=U˙C⎭⎬⎫
线电流与相电流的关系
I ˙ A = 3 I ˙ A ′ B ′ ∠ − 30 ° I ˙ B = 3 I ˙ B ′ C ′ ∠ − 30 ° I ˙ C = 3 I ˙ C ′ A ′ ∠ − 30 ° } \left.\begin{matrix}\dot{I}_{A} = \sqrt{3}\dot{I}_{A'B'}∠-30° \\\dot{I}_{B} = \sqrt{3}\dot{I}_{B'C'}∠-30° \\\dot{I}_{C} = \sqrt{3}\dot{I}_{C'A'}∠-30° \end{matrix}\right\} I˙A=3I˙A′B′∠−30°I˙B=3I˙B′C′∠−30°I˙C=3I˙C′A′∠−30°⎭⎬⎫
(4) △ − Y \triangle-Y △−Y
线电压与相电压的关系
U ˙ A B = U ˙ A U ˙ B C = U ˙ B U ˙ C A = U ˙ C } \left.\begin{matrix}\dot{U}_{AB} =\dot{U}_A \\\dot{U}_{BC} = \dot{U}_B \\\dot{U}_{CA} =\dot{U}_C \end{matrix}\right\} U˙AB=U˙AU˙BC=U˙BU˙CA=U˙C⎭⎬⎫
线电流与相电流的关系
I ˙ A = I ˙ A ′ B ′ I ˙ B = I ˙ B ′ C ′ I ˙ C = I ˙ C ′ A ′ } \left.\begin{matrix}\dot{I}_{A} = \dot{I}_{A'B'} \\\dot{I}_{B} = \dot{I}_{B'C'} \\\dot{I}_{C} = \dot{I}_{C'A'} \end{matrix}\right\} I˙A=I˙A′B′I˙B=I˙B′C′I˙C=I˙C′A′⎭⎬⎫