I1*?rk*?xk*I2*RL*U1*2-9：
?rm*xm*Im*??U2*
解：（1）空载时，U0?UN,则U0*?1，计算激磁阻抗： zm*?11??50 I0*0.02rm*?p0*133125000??2.66 22I0*0.0222xm*?zm*?rm*?49.93
短路时，Ik?IN,则Ik*?1，计算短路阻抗：
zk*?uk*?0.105
rk*?pkN*?600?0.0048
12500022xk*?zk*?rk*?0.1049
??1?0?，则I??1??36.87? （2）设U2*2*???U??I??r?jx???1?0??1??36.87??0.0048?j0.1049?U1*2*2*k*k* ?1.0699??175.7?
??I??I??1.0699??175.7???1??36.87??1.015?142.26? I1*m*2*2.66?j49.93（3）?U??U1*?1??100%??1.0699?1??100%?6.99% ??P2U2*I2*cos?21?1?cos36.87????99.27% P1U1*I1*cos?11.0699?1.015?cos??175.7?142.26??实用公式：
?U??(rk*cos?2?xk*sin?2)?100% ?1?0.0048?0.8?0.1049?0.6??100%?6.678%
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?＝βSNcos?21?125000?0.8??99.27% 22βSNcos?2?p0??PKN1?125000?0.8?133?1?600（4）当?????
p0133??0.471时，有最大效率： PkN600?max＝β?SNcos?20.471?125000?0.8??99.44"??βSNcos?2?p0??PKN0.471?125000?0.8?133?0.471?600
p54：3-1
B(X)b(x)A(Z)(a)c(y)Dd0
Dy11
C(Y)
B(X)bxyzcA(Z)(a)Dy11
C(Y)
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Bc(y)XYZA(a,z)Cb(x)Yd7
Yy10
BbxyzcXYZCA(a)Yy10
p54：3-2
BbxyzcXYZCA(a)Yy10
BcXYZbA(a)CYd9- 8 -
B(X)A(Z)(a)C(Y)b(x)Dd4
c(y)P69:4-1 解：（1）二次空载时对称：变压器结构和参数相同，二次空载时，一次绕组通过三相对称空载电流，产生三相对称磁通，在二次的感应电动势相同且对称，即一、二次侧相、线电压对称。
（2）二次接对称负载时：同一次电流对称、磁通对称，二次感应感应电动势相同且对称，所以一、二次侧相、线电压对称。 （3）假设a相接负载：
rm??p0?11??4Z??20 ，m?I02?0.0520.0522xm??zm202?42?19.6 ??rm??zk??uk??0.05，rk??ua??0.02
22xk??zk0.052?0.022?0.046 ??rk??
Ib??Ic??0， Ua??I?ZL?. ①边界条件：Ia??I?， ??1?1???2?Ia???3(Ia??aIb??aIc?)?3I?????1?1??2②a相序电流：?Ia???(Ia??aIb??aIc?)?I?
33???1?1????Ia0??3(Ia??Ib??Ic?)?3I????????③各序网络图（可直接画总图，该题中用标么值表示）有：
?Ua??UA???(Ia???Ia??)Zk??Ia0?(Z2??Zm0?)同理：?Ub??UB???(Ib???Ib??)Zk??Ib0?(Z2??Zm0?) ?Uc??UC???(Ic???Ic??)Zk??Ic0?(Z2??Zm0?)
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???????????????
④由图可得：
??I??I???I???I???Ia??a??a0?A??A????1?0??UA??2zk??z2??zm0??3RL?
12(0.02?j0.046)?(0.02?j0.046)?4?j19.6?32?0.04767?109.7???3I??0.143?109.7? I?a????I??0.143?109.7?,I??I??0 ⑤二次侧相（线）电流：Ia??b?c?一次侧相（线）电流（注：无零序）：
??I??I???I??I???2?0.143?109.7??0.095??70.3? IA?A??A??a??a??3??I??I???a2I??aI??1?0.143?109.7??0.04767?109.7? IB?B??B??a??a??3??I??I???aI??a2I??1?0.143?109.7??0.04767?109.7? IB?C??C??a??a??3二次侧相电压(不对称)：
?Ua??UA???(Ia???Ia??)Zk??Ia0?(Z2??Zm0?)??R??0.143?109.7???0.143?70.3? 或??I?L???????同理：?Ub??UB???(Ib???Ib??)Zk??Ib0?(Z2??Zm0?)?Z?I?(Z?Z) ?1?-120??(a?a2)Ia0?k?a0?2?m?????
?1.756??145.23? ?Uc??UC???(Ic???Ic??)Zk??Ic0?(Z2??Zm0?)?1.1617?153.1??????一次侧相电压(不对称)：
???U??0.143??70.3?UA?a????U??1.756??145.23? UB?b????U??1.617?153.1?Uc?c?一、二次侧线电压(对称)： ???1.724?30.18?U??UAB?ab???UBC???Ubc??1.733??90.01? ???U??1.724?149.83?UcA?ca?
p83：5-2
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