[工学]第4章-供电与用电

1、2e1e3e 240sin120sinsin321 tEetEetEemmm 120sin tEm1230EEE+=1E2E3E 240sin120sinsin321 tEetEetEemmm 120sin tEm1201200321 EEEEEECe11ue=1U2U3U1u2u3u22ue=33ue=1201200321 PPPUUUUUUCe12u23u31u122331uuu1u2u2112UUU 3223UUU 1331UUU Ce2U-12U2U1U3U1212UUU=-2U1U3U23U31U12U303112 UU3033033133123223 UUUUUUUU303 PLU

2、U线线电电压压相相电电压压 LPUU232UU=313UU=121UU=lpUU=31u12u23u31u12u23u2e1e3e1Li2Li3Li1i2i3i123 III、 、123 LLLIII、11IIL 22IIL 33IIL LPII=123NIIII=+NI-零零线线电电流流Ni1U12U3U31U12U303电压电压相电压，线电压超前相相电压，线电压超前相线电压线电压 303303303331223112 UUUUUU2U1U3U23U31U12U2U3i2Li1LiNi3Li1i2iCe3e2e1e303 PLUUZUIIPPL 求：各相、各线及中线电流求：各相、各线及中线电

3、流3LI1LINI2LI1I2I3I1203120303312312 lllUUUUUU解：解：(1)相电流相电流3031121 UU1U30 lU1502 lUU903 lUU3011 RURUIl24022 LlLXUjXUI18033 ClCXUjXUI(2) 线电流线电流(3)中线电流中线电流332211IIIIIILLL 321LLLNIIII 31U12U23UNI3U1U2U2I3I1I(2) 线电流线电流(3)中线电流中线电流解：解：(1)相电流相电流301 RUIl2402 LlXUI1803 ClXUI332211IIIIIILLL 321LLLNIIII 18024030

4、 ClLllXUXURU1LI2LI3LI3U1U2U ZZZZZ321ZUIIL111 120122 IIIL240133 IIIL0321 IIIIN中中线线电电流流 1230NLLLIIII=+=负载对称时零线是否可以取消？负载对称时零线是否可以取消？答：三相完全对称时，零线可以取消。称为答：三相完全对称时，零线可以取消。称为 三相三线制三相三线制。3eCe2e1e1201200321 EEEEEE1LI2LI3LI1E2E3E+-RRRR+1E2E3E-+-+-RRRRNNABC1LI2LI3LI1LI2LI3LI1E2E3E+-RRRR1LI2LI3LI+1E2E3E-+-+-RRR

5、RNNABC1LI2LI3LI 4842PUR22212022033120220330220RRRRRRRRRUNN 12011012055055 120557 .475 .27 j12055 NNU12i31i23i3Li2Li1Li31u12u23u121212UIZ=232323UIZ=313131UIZ=11231LIII=-22312LIII=-33123LIII=-plUU=31U12U23U2LI3LI12I31I23I31I-1LIL1L212I31I1LIL3012 LUU31121IIIL 303121 IIL303232 IIL303313 IIL303 PLII123PPPP=+三相总有功功率：三相总有功功率：123QQQQ=+三相总无功功率：三相总无功功率：22SPQ=+三相总视在功率：三相总视在功率： cos3cos3ppllIUIUP sin3llIUQllIUS3 Ce3e2e1eCe303 plplUUIIplplUUII 303*1W*2W*3W*13u1i1u1Z2Z2W*1W*3Z2u3u2i3i23u电击伤害的程度电击伤害的程度取决于通过人体取决于通过人体电流的大小、持续时间、电流的电流的大小、持续时间、电流的频率及电流通过人体的途径等。频率及电流通过人体的途径等。RRCR0IbIeI