一台三相4极、星形联结的异步电动机,额定值为:P N =1.7kW,U N =380V,I N =3.9A,n N =1445r/min。今拖动一恒转矩负载T L =11.38N·m连续运行,此时定子绕组平均已达到绝缘材料允许的温度上限。若电网电压下降为300V,在上述负载下电动机的转速为1400r/min,求此时电动机的铜耗为原来的多少倍?在此电网电压下该电动机能否长期运行下去(忽略励磁电流和机械损耗)?
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