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,电机学习题课,*,Electric Machinery,*,1,3-13,一台四极,82kW,,,230V,,,970r/min,的并励发电机,,R,(,75,0,),0.0259,,,R,f,(,75,0,),22.8,额定负载时励磁回路中 串入,3.5,的调节电阻,电刷压降为,2V,,铁耗和机械损耗共,2.5kW,,杂散损耗为额定功率的,0.5,,试求额定负载时发电机的输入功率、电磁功率和效率。,分析:并励发电机,额定负载时:,I=P/U,N,=82000/230=356.52A,I,a,I+I,f,365.265A,P,e,P,2,+I,a,2,R,+,2U,s,I,a,I,f,2,R,f,88.197kW,或者:,P,e,E,a,I,a,(U+I,a,R+2U,s,)I,a,=(230+365.27*0.0259+2)*365.265,88.197kW,(推荐),2,P,1,P,e,P,0,88.198,2.5,0.5,82,91.108kW,3,3-16,一台,17kW,、,220V,的并励直流电动机,电枢总电阻,Ra,0.1,欧,电刷压降为,2V,,在额定电压下电枢电流为,100A,,转速为,1450r/min,并励绕组与一变阻器串联以限制励磁电流为,4.3A,。当变阻器短路时,励磁电流为,9A,,转速降低到,850r/min,电动机带有恒转矩负载,机械损耗等不计,试计算,(,1,)励磁绕组的电阻和变阻器电阻(,2,)变阻器短路后,电枢电流的稳态值;(,3,)电磁转矩值,励磁支路总电阻,R,220/4.3,51.16,R,f,=220/9=24.44,R,滑,26.72,T,l,不变,机械损耗等不计,4,5,3-17,一台,96kW,的并励直流电动机,额定电压为,440V,,额定电流为,255A,额定励磁电流为,5A,,额定转速为,500r/min,,电枢电阻为,0.07,欧,电刷压降,2,Us=2V,,,不计电枢反应,试求,(,1,)电动机的额定输出转距;(,2,)额定电流时的电磁转矩(,3,)电动机的空载转速,。,电磁转矩,输出转矩,6,
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