三相鼠笼异步电动机的工作特性

./4—1三相鼠笼异步电动机的工作特性实验目的掌握三相异步电动机的空载、堵转和负载试验的方法。用直接负载法测取三相鼠笼有电动机的工作特性。测定三相鼠笼异步电动机的参数。预习要点异步电动机的工作特性指哪些特征？异步电动机的等效电路有哪些参数？它们的物理意义是什么？工作特性和参数的测定方法。实验设备序号DDSZ-1名称数量1DD03导轨、测速发电机及转速表1件2DJ23校正过的直流电机1件3DJ16三相鼠笼异步电动机1件4D33交流电压表1件5D32交流电流表1件6D34-3单三相智能功率、功率因数表1件7D31直流电压、毫安、安培表1件8D42三相可调电阻器1件9D51波形测试及开关板1件测量定子绕组的冷态直流电阻将电机在室放置一段时间,用温度计测量电机绕组端部或铁心的温度与冷却介质温度之差不超过2K时,即为世纪冷态。记录此时的温度和测量定子绕组的直流电阻,此阻值即为冷态直流电阻。用伏安法测定子绕组电阻,测量线路如图4-1.直流电源用主控屏上电枢电源先调到50V。开关S1、S2选用D51挂箱,R用D42挂箱上1800Ω可调电阻。图4-1三相交流绕组电阻测定量程的选择：测量时通过的测量电流应小于额定电流的20%,约为50mA,因而直流电流表的量程用200mA档。三相鼠笼式异步电动机定子一相绕组的电阻约为50Ω,因而当流过的电流为50mA时二端电压约为2.5V,所以直流电压表量程用20V档。按图4-1接线。把R调至最大位置,合上开关S1,调节直流电源及R阻值使试验电流不超过电机额定电流的20%,以防因试验电流过大而引起绕组的温度上升,读取电流值,再接通开关S2读取电压值。读完后,先打开开关S2,再打开开关S1。调节R使A表分别为50mA,40mA,30mA测取三次,取其平均值,测量定子三相绕组的电阻值,采集数据：表4-1绕组I绕组II绕组IIII<mA>40503029.9840.0050.1729.9239.9950.11U<V>1.7062.1171.2801.2571.6782.1051.2531.6772.014R<Ω>42.6542.3442.6741.9341.9541.9641.8841.9440.19负载情况针对DDSZ-1电机教学实验台空载实验按图4-2接线。电机绕组为△接法〔Un=220V,直接与测速发电机同轴联接,负载电机DJ23不接。把交流调压器调至电压最小位置,接通电源,逐渐升高电压,使电机启动旋转,观察电机旋转方向。并使电机旋转方向符合要求〔如果转向不符合要求需要调整相序时,必须切断电源。保持电动机在额定电压下空载运行数分钟,使机械损耗达到稳定后再进行试验。图4-3三相鼠笼式异步电动机试验接线图保持电动机在额定电压下空载运行数分钟,使机械损耗达到稳定后再进行试验。调节电压由1.2倍额定电压开始逐渐降低电压,直至电流或动率显著增大为止。在这围读取空载电压、空载电流、空载功率。在测取空载实验数据时,在额定电压附近多测几个点,共取数据7~9组采集于表4-2。表4-2序号U

OL<V>IOL<A>>P0<W>COSφUABUBCUCAUOLIAIBICIOLPIPP01259.6256259.8258.50.3020.2820.2820.28952.08-24.5227.560.1232249.8245.9249.5248.40.2850.2670.2670.27347.81-22.0025.810.1293228.0224.9228.12270.2570.2390.2400.24540.48-16.6523.830.1434221.6218.6221.9220.70.2480.2300.2340.23738.01-12.5625.450.1625220.4217.4220.4219.40.2460.2300.2370.23837.83-15.0122.820.1466220.0217.4219.8222.80.2450.2290.2300.23537.47-14.8722.60.1447216.2214.2217.0215.80.2400.2250.2290.23136.62-14.3422.280.1498210.1207.9211.0209.70.2340.2160.2220.22434.95-13.2021.750.1549133.8133.4134.7134.00.16490.15370.15870.15916.68-1.0515.630.2451080.4079.0080.8080.10.16540.1530.15190.15712.602.4315.030.3981162.9661.8563.1162.-640.2160.2070.2040.20912.932.8415.770.4021255.1354.2254.8254.720.2900.3870.3850.35417.77-1.4316.340.281短路实验测量接线图同图4-2,。用制动工具把三相电机堵住。制动工具可用DD05上的圆盘固定在电机轴上,螺杆装在圆盘上。调压器退至零,合上交流电源,调节调压器使之逐渐升压到短路电流到1.2倍额定电流,再逐渐降压至0.3倍额定电流为止。在这围读取短路电压、短路电流、短路功率。共读取5~6组采集于表4-3中。表4-3序号U

KL<V>IKL<A>>PK<W>COSφKUABUBCUCAUKLIAIBICIKLPIPIIIPK175.8674.6375.7575.410.6200.6150.6150.61739.84-0.9738.870.278265.0264.2165.4764.90.5040.4970.5020.50127.55-1.4526.100.266358.9157.4059.1058.470.4380.4250.4310.43127.55-1.4526.100.266450.2849.0450.1249.810.3440.3370.3380.41013.95-1.7712.180.199541.7340.4941.7241.310.2570.2490.2520.2538.35-1.526.830.217633.8533.4735.0534.120.1850.17350.1860.1824.79-1.123.670.197730.0128.7630.0329.600.14460.13570.13750.1393.14-0.862.280.185负载实验测量接线图如图4-2.同轴联接负载电机。图中Rf用D42上1800Ω阻值,RL用D42上1800Ω阻值加上900Ω并联900Ω共2250Ω阻值。合上交流电源,调节调压器使之逐渐升压至额定电压保持不变。合上校正过的直流电机的励磁电源,调节励磁电流至校正值〔50mA或100mA并保持不变。调节负载电阻RL〔先调节1800Ω电阻,调至零后用导线短接再调节450Ω电阻,使异步电动机的定子电流逐渐上升,直至电流上升到1.25倍额定电流为止。从这负载开始,逐渐减小负载直至空载,在这围读取异步电动机的定子电流、输入功率、转速、直流电机的负载电流IF等数据。共取数据8~9组采集于表4-4中表4-4U1φ=U1N=220V<△>If=100.4mA序号I1L<A>P1<W>IF<A>T2<N*m>N<r/min>IAIBICI1LPIPIIP110.6210.6010.5960.606130.949.14180.040.6830.920137820.5050.4850.4820.491106.9335.28142.210.5180.730141130.4550.4420.4300.44295.4527.53122.980.4320.654142440.4060.3860.3850.39285.0220.68105.70.3570.556143850.3310.3070.3080.31566.090.69666.790.2010.390145960.3000.2800.2810.28758.001.1359.130.1350.340146870.2870.2690.270.0.27554.30-1.4552.850.1050.290147180.2770.2590.2560.26451.19-4.0447.150.0770.275147990.2540.2380.2400.24442.15-10.8331.3200.1851485六、实验报告1、计算基准工作温度时的相电阻由实验直接测得每相电阻值,此值为实际冷态电阻值。冷态温度为室温。按下式换算到基准工作温度时的定子绕组相电阻：式中ｒ1ref——换算到基准工作温度时定子绕组的相电阻,Ω；ｒ1c——定子绕组的实际冷态相电阻,Ω；θref——基准工作温度,对于E级绝缘为75℃θc——实际冷态时定子绕组的温度,℃；2.作空载特性曲线：IOL、PO、COSφ0=f<UOL>用MATLAB作图如下：PO=f<UOL>IOL=f<UOL>COSφ0=f<UOL>3.作短路特性曲线：IKL、PK=f<UKL>用MATLAB作图如下：IKL=f<UKL>PK=f<UKL>由空载、短路实验数据求异步电机的等效电路参数由短路实验数据求短路参数短路阻抗：短路电阻：短路电抗：式中UKφ=UKL,IKL=IKL/30.5,PK电动机堵转时的相电压,相电流,三相短路功率〔△接法。转子电阻的折合值：式中r1c是没有折合得75oC时实际值定、转子漏抗：短路参数短路阻抗ZK<Ω>短路电阻rK<Ω>短路电抗XK<Ω>定转子漏抗X1.<Ω>数值211.7102.1185.592.8224.4104.0198.899.4235.0104.0210.7105.4210.472.5197.598.6282.9106.7262.0131.0324.7110.8304.5152.3372.9118.0246.1123.0由空载试验数据求激磁回路参数空载阻抗空载电阻空载电抗式中UOφ=UOL,IOφ=IOL/30.5,P0电动机堵转时的相电压,相电流,三相短路功率〔△接法。激磁电抗激磁电阻空载阻抗Z0<KΩ>空载电阻RO<KΩ>空载电阻X0<KΩ>激磁电抗Xm<KΩ>1.5490.3301.5130.7571.5760.3461.5470.7741.6050.3971.5550.7781.6130.4531.5480.7741.5970.4031.5450.7731.6420.4091.5900.7951.6180.4181.5630.7821.6210.4331.5620.7811.4600.6181.3230.6620.8840.6100.6400.3200.5190.3610.3730.1870.2680.1300.3440.172式中PFe为额定电压时的铁耗,由图4-4确定做工作特性曲线P1、I1、η、S、cosφ1=f<P2>由负载试验数据计算工作特性,填入表4-5中。表4-5U1=220V<△>If=100.4mA序号电动机输入电动机输出计算值I1φ<A>P1<W>T2<N*m>n<r/min>P2<W>S<%>η<%>cosφ110.350180.040.9201378133.18.1373.90.76620.283142.210.7301411108.25.9376.10.76130.255122.980.654142497.85.0679.50.73140.226105.70.556143884.04.1379.50.70950.17966.790.390145959.72.7389.40.56560.16659.130.340146852.42.1388.60.54070.15952.850.290147144.81.9384.80.50480.15247.150.275147942.71.4090.60.47090.14131.320.185148528.81.0092.00.337用MATLAB作图如下由损耗分析法求额定负载时的效率电动机的损耗有：铁耗：PFe机械损耗：PCU1=3I21φr1转子铜耗：PCU2=PemS/100杂散损耗Pad取为额定负载时输入功率的0.5%。式中Pem电磁功率,W;P0’=PFe+Pmec=P0-I2Oφr1为了分离铁耗和机械损耗,作曲线P0’=f<U20>,如图4-4延长曲线的直线部分与纵轴相较于K点,K点的纵坐标即为电动机的机械损耗Pmec,过K点作平行于横轴的直线,可得不同电压的铁耗PFe。电机的总损耗于是求得额定负载时的效率为：式中P1、S、I1由工作特性