(精品)《电机学》课后习题答案 下载本文

Uk??UKU3?5503?317.55(V)

U1N?I1N?N?k?U1?5773.676300?0.916 Zb?2N??5773.67323.35?17.856(?)

'Zm?U2N?I0??10 ?6.34.73?1331.92(?)23'Rm?P0?I0?'''2?Zm?Rm?1331.922?93.422?1328.64? ?22404.732?100.12(?) Xm折算到高压侧:

'Zm?k2Zm?0.9162?1331.92?1117.6(?)

Zm2** Rm?0.916?100.12?84(?) RmZm?Z??1117.6?8417.856?4.7 17.856?62.59'Xm?0.9162?1328.64?1114.8(?) Xm?1114.817.856?62.43

短路参数:

Zk?Rk?Uk?Ik?Pk?I2k?*0.982?0.055 Zk?17.856?317.55323.35?0.982(?)*0.0575973.33?17.856?0.0032 ?323.352?0.057 Rk*Xk?Z*2k*2?Rk?0.0552?0.00322?0.0549

*Rk*xk**(2) ??1 ?U?0?Rkcos?2?Xksin?2 ∴tg?2????0.00320.0549??0.05829

。∴?2??3.3359 ∴是容性负载 cos?2?0.998(超前)

**?U(3)??1 d??Rsin??Xk2kcos?2?0 d?2∴tg?2?*Xk*Rk。??86.66?0.0549?17.156 (感性)cos?2?0.0583(滞后) 20.0032?Umax?0.0032?0.0583?0.0549?sin86.66?0.055

(4) ?m?P0PkN2(即P0??mPkN时效率最大)= 2240?35973.3?3=0.06124

?max?1?

2P0??mPkN?mSNcos?2?P0??mPkN6720?0.06124?179205623.22?17319.680 ?0.06124?5600?1??99.6330?10?0.9?6720?0.06124?179202981.16?10?5623.223.49 有一台三相变压器,SN?5600kVA,U1N/U2N?10/6.3kV,Yd11联接组。变

压器的空载及短路试验数据为: 试验名称 空载 短路

线电压 U1/V 6300 550 线电流 I1/A 三相功率P/W 7.4 323.3

备注 电压加在低压侧 电压加在高压6800 18000

侧 试求: (1)变压器参数的实际值及标幺值;

(2)求满载cos?2?0.8(滞后)时,电压调整率?U及二次侧

电压U2和效率;

(3)求cos?2?0.8(滞后)时的最大效率。 解:U1N??103?103?5773.67(V) I1N??5600?1033?10?103?323.35(A)

U2N??6300(V) I2N??56003?6300?13?296.3(A)

3空载低压侧P0??68003?2266.7(W) I0??7.4'∴Zm?U2N?I0??4.27(A)

' R?6300?1475.4(?)m?4.27P0?2I0??2266.74.272?124.32(?)

U'5773.67N? ?Xm?1475.42?124.322?1470.15(?)变比k?U16300?0.9162N?Zm?k2zm?0.9162?1475.4?1238(?) Rm?0.9162?124.32?104.3(?) xm?0.9162?1470.15?1233.5(?)

短路参数计算: Uk??550?317.55(V) Ik??323.3(A) 3317.55k?Pk??180003?6000(W) ZK?U Rk?Ik??323.3?0.9822(?)Pk?2Ik?6000?323.32?0.0574(?)

5773.621N? Xk?0.98222?0.05742?0.9805(?) Zb?UI1N??323.35?17.86***Zm?123817.86?69.32 Rm?104.317.86?5.84 Xm?69.322?5.842?69.07 ***Zk?0.982217.86?0.055Rk?0.057417.86?0.003214 Xk?0.980517.86?0.0549 **(2) ?U??(Rkcos?2?Xksin?2)?1?(0.003214?0.8?0.0549?0.6)?3.5500

?U?1?U2 ∴U2??(1??U)U2N??(1?0.0355)?6300?6076.3(V)

2NU??1??SP0??2PkN2Ncos?2?R0??PkN6800?1?18000?1?1?5600?10?99.4500 3?0.8?6800?1?18000(3) ?m?2P0PkN?36800180002?0.61464

6800?0.6146?18000??1?0.6146?5600?99.5100 ?10?0.8?6800?0.6146?18000

3.50 一台三相变压器SN?750kVA,U1N/U2N?10000/400V,Yy联接,短路阻抗

Zk?1.40?j6.48?,负载阻抗ZL?0.20?j0.07?,试求:

(1)一次侧加额定电压时,一二次侧电流和二次侧电压; (2)输入、输出功率及效率。 k?U1N?U2N??1000040033?25

'ZL?k2zL?252?(0.20?j0.07)?125?j43.75?132.43519.29。

(1) U1N??100003&?5773.670。 ?5773.67(V) 设U1N?'。(?)∴Z?Zk?ZL?1.4?j6.48?125?j43.75?126.4?j50.23?13621.67

&5773.670。。1N?&?U ∴I ?45?21.67(A)。?42.1Z13621.67。’‘。&&U?IZ?42.45-21.67?132.43519.29(V)=5621.9-2.38。 21L''∴I1?I2?42.45(A) I2?kI2?1061(A) U2?3U2R?5621.9?'325?389.5(V)

。(kW)(2)P 1?3U1I1cos?1?3?5773.67?42.45?cos21.67?683.3PU2I2cos?2?3?389.5?1061?cos(?u??I)?cos(?2.38?21.67)?675.6(kW)2?3 ??P2P100 ?10000?675.6683.3?1000?98.8703.51(a)

A B C · ·· X Y Z zxy A a Cb· · · Bca b c

联结组别为:Yy10 (b)

A B C · ·· A X Y Z cba· · · zxy (c)

ABC· · · Z Y X x y z · ·· ab c (4)

ABC· · · X Y Z b c a · · · yz x ca C bB联结组别:Yd3

A ac C bB

联结组别:Dy1 A(X) b(z)c(x) a(y)C(Y) B(Z) 联结组别:Dd6