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1、某四极直流电机,电枢槽数z=36,单迭绕组,每槽导体数为6,每极磁通2.2*10e-2Wb,电枢电流Ia=800A,问此时电磁转矩为多少?如改为单波绕组,保持支路电流不变,其电磁转矩为多少?解:电机内的总导体数N=6Z=36*6=216,单迭绕组时:a=p=2222162.210800605.04223.14162MaapNTCIINma改为单波绕组时,1a,若要保持支路电流不变,8002221400222aaaIIaiaAa222162.210400605.04223.14161MaapNTCIINma2、某他励直流电动机额定电压UN=220V,额定电流IN=10A,额定转速nN=1500r/min,电枢回路总电阻Ra=0.5Ohm,试求:(1)额定负载时的电磁功率和电磁转矩;(2)保持额定时励磁电流及总负载转矩不变而端电压降为190V,则稳定后的电枢电流与转速为多少?(电枢反应忽略不计)。解:(1)220100.5102150MNaaNNaNPPEIUIRIW21506013.687223.1416150060NNNNNPPTNmn(3)励磁电流不变时磁通不变,总负载转矩也不变,所以10ZaNMTIIAC不变,19010515001290.70/min220105aNNaNNaNNNaEUIRnnnrEUIR3、某并励直流电动机额定电压UN=220V,额定电流IN=75A,额定转速nN=1000r/min,电枢回路总电阻Ra=0.26Ohm,额定时励磁回路总电阻Rfn=91Ohm,铁耗及附加损耗pFe+pdelta=600W,机械损耗POhm=198W,电枢反应去磁作用不。试求:(1)额定运行时的电磁转矩T与输出转矩TN;(2)理想空载转速;(3)实际空载电流I0及实际空载转速。解:(1)0600198798FeppppW12212207516.52202.4291752.4272.5872.580.261369.642.42220532.4165001369.64532.414597.9614597.96223.160NNNfNfnaNNfNcuaaNacuffNNMcuacufMMNNPUIkWUIARIIIApIRWpIUWPPppWPPTn139.4416100060Nm1369.64532.46001982700.04220752700.04131.78223.141610006060cuacufFeNNNNNNppppppWUIpPTNmn(2)22072.580.260.201131000NaNaaNeNNNUIRECnn002201093.820.20113NeUnC(3)0139.4131.787.62NTTTNm9.559.550.201131.921MNeNCC007.623.9671.921aMNTIAC0002203.9670.261088.69/min0.20113NaaeUIRnrC5、他励直流电动机额定数据如下:PN=60kW,UN=220V,IN=350A,nN=1000RPM,试问:(1)如果将该机直接起动,则启动电流为多少?(2)为使启动电流限制在2IN,应在电枢回路串入多大电阻?(3)如果采用降压启动且使启动电流限制为2IN,端电压应降为多少?解:(1)221220350600000.069423502NNNaNUIPRI2203170.590.0694NaaUIAR(2)122200.06940.24522350NaaNURRRRI(3)1223500.069448.58NaUIRV6、某他励直流电动机额定数据如下:PN=3kW,UN=220V,IN=18A,nN=1000RPM。电枢回路总电阻Ra=0.8Ohm。试求:(1)为使该机在额定状态下进行能耗制动停机,要求最大制动电流不超过2In,求制动电阻值;(2)在项(1)的制动电阻时,如负载为Tz=0.8TN位能转矩,求电机在能耗制动后的稳定速度;(3)设该机带动Tz=TN位能负载运行于额定状态,采用能耗制动使之最终以500rpm的速度放下重物,求制动电阻及该电阻所对应的最大制动电流;(4)该机采用能耗制动将Tz=TN的位能负载稳速下放时,所能达到的最低下放转速为多少?(5)若该机在额定工况下采用能耗制动停机而不接制动电阻,则制动电流为额定电流多少倍?解:(1)220180.80.20561000NNaeNNUIRCn10.205610000.84.912218eNNeNNZaaNCnCnRRRII(2)0.80.80.81814.4NzzNMNMNTTIIACC0.814.456.03/min0.2056azzeNRnIrC(3)18NzzNMNMNTTIIACC10.20565000.84.9118eNNeNNZaazCnCnRRRII(4)18NzzNMNMNTTIIACC0.81870.04/min0.2056azzeNRnIrC(5)10000.20562570.80NeNaaznCIARR25714.2818aNII7、他励直流电动及额定数据为:PN=29kW,UN=440V,IN=76A,nN=1000RPM,Ra=0.377Ohm;试问:(1)该机以500rpm的速度吊起Tz=0.8TN负载转矩,在电枢回路应串多大电阻?(2)用哪几种方法可使Tz=0.8TN的位能负载以500rpm的速度稳速下放?求每种方法的电枢回路串接的电阻值。解:(1)440760.3770.41131000NNaeNNUIRCn04401069.78/min0.377NeNUnrC0.80.80.87660.8NzaNMNMNTTIIACC4400.41135000.3773.47760.8NeNaaUCnRRI(2)可采用串接电阻能耗制动的方法10.41135000.3773.00560.8eNeNZaazCnCnRRRII8、某三相感应电动机的额定数据如下:PN=30kW,UN=380V,nN=1450r/min,cosφN=0.80,ηN=88%,fN=50Hz,试求:(1)该机的极数;(2)额定转速差;(3)额定电流。解:(1)该机的同步转速可以写成:116060503000/minfnrppp当极对数p=2时,n1=1500,略高于n1,所以极对数必为:1160605021500fpn(2)11150014500.0331500NNnnSn(3)3103000064.743cos33800.880.8NNNNNPIAU9、某三相四极50Hz感应电动机,PN=10kW,UN=380V,nN=1455rpm,定子绕组三角形接法。R1=1.375Ohm,X1=2.43Ohm,r2=1.04Ohm,X2=4.4Ohm,rm=8.34Ohm,Xm=82.6Ohm。额定负载时pOhm+pdelta=205W。试用简化等值电路计算额定负载时的定子电流、功率因数、输入功率和效率。解:13033800658.180NUUV'11111'122112658.1801.3758.342.4382.60.877.647.6983.48150014550.031500658.1801.041.3752.434.40.0317.633.3417.94mmmNNUIrrjXXjjAnnSnUIrjrjXXSj''12111169.270.877.6417.633.3418.510.9821.5130.69coscos30.690.8610000100%100%100%82.1%3cos338021.510.86mNNNNNNNNAIIIjjjAPPPUI10、某三相四极50Hz感应电动机,已知输入功率P1=10.7kW,定子铜耗Pcu1=450W,铁耗pfe=200W,转差率S=0.029。试求此时该机的电磁功率PM,总机械功率Pohm,转子铜耗Pcu2及电磁转矩T各为多少?解:111070045020010050MCuFePPppW21111110.029100509758.55291.456060501500/min2221500157.08/60601005063.98157.08MCuMMPSPWPPPWfnrpnradsPTNm11、某三相绕绕式感应电动机的额定数据如下:PN=7.5kW,UN=380V,IN=15.1A,nN=1450rpm,λM=2.0。试求:(1)临界转差率Sm和最大转矩Tm;(2)写出固有机械特性实用表达式;(3)该机的固有启动转矩倍数KM。解:(1)1160605030001500/min2fnrpp11150014500.0331500NNnnSn2210.0332210.1247.59550/950049.141450249.1498.28mNMMNNNmMNSSTPnNmTTNm(2)固有机械特性为22298.2824.3730.1240.0150.124mmmTSTSSSSSSS(3)2220.4910.1240.1241mNQNmmTTTTSSSS0.49QMNTKT1、一台并励直流电动机,额定功率PN=96KW,额定电压UN=440V,额定电流IN=255A,IfN=5A,额定转速为nN=500r/min,电枢回路总电阻Ra=0.078Ω,电枢反应忽略不计,试求:1、额定运行时的电磁功率;2、额定输出转矩;3、额定电磁转矩;4、理想空载转速。1)AIIIafNNN25052555.420250078.0440RaIaUEaNNNVWEaIaPNNM1051255.4202502)mNnPPTNNNNN39.183450014.32609600060/2/3)mNnPPTNMNM76.200850014.326010512560/2/4)NNNnEaCe841.05005.420min/19.523841.04400rCeUnNNA2、某并励直流电动机额定数据如下:PN=7.2KW,UN=110V,nN=900r/min,Ra=0.08Ω,ηN=85%,IfN=2A。保持总负载转矩不变,若在电枢回路中突然串入0.2Ω的电阻,问串入瞬间的电磁转矩是多少?稳定运行的转速是多少?AUPINNNN7785.011010002.7AIIIafNNN75277
本文标题:电机与拖动答案
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