15级题库 电机与拖动基础试题库及答案

2） s?RP?r2?sg?0.4?0.023?0.03?1?0.552

r20.023 n?(1?s)n1?(1?0.552)?600?268.8r/min

6、一台△联结的4极三相异步电动机，UN?380V,nN?1470r/min

'r1?r2'?0.072?,X1?X2?0.06?,fN?50Hz试求：全压起动时的定子电流（略空载电流）及其功率因数、起动转矩倍数；Y/△起动时的起动电流、起动转矩。 解：全压起动时的定子电流、功率因数：

Ist?相?cos?1?UN?(r1?r)?(X1?X)r1?r2'(r1?r)?X1?X'22'22'22?380(0.072?0.072)?(0.2?0.2)0.072?0.072(0.072?0.072)?(0.2?0.2)222?893.84A

?0.3384

? 22?2求起动转矩倍数：

sN?n1?nN1500?1470??0.02 n115002'm1pU1r2s

TN?2 2?f1r1?r2's?X1?X2 ?????23?23802?0.072/0.02??727.68N?m

0.0722??2??50?(0.072?)?(0.2?0.2)2?0.02??3?2?3802?0.072Tst??1098.64N?m222??50(0.072?2)?(0.2?2)??

起动转矩倍数：

Y/△起动时的起动电流、起动转矩：

KM?Tst1098.64??1.51TN727.68I'st? Tst'?

Ist?3?893.84??516A 33Tst1098.64??366.2N?m 33