【单选题】
带转速微分负反馈的直流双闭环调速系统的动态转速大大降低，RdnCdn值越大，___。
A. 静态转速降越低，恢复时间越长
B. 动态转速降越低，恢复时间越长
C. 静态转速降越低，恢复时间越短
D. 动态转速降越低，恢复时间越短
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答案
B
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对恒转矩负载，交流调压调速系统要获得实际应用，必须具备的两个条件是采用___。
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在闭环控制交流调压调速系统中，负载变化范围受限于___时的机械特性，超出此范围闭环系统便失去控制能力。
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变频器常见的频率给定方式主要有：模拟信号给定、操作器键盘给定、控制输入端给定及通信方式给定等，在PLC控制系统时不采用___方式。
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恒功率负载变频调速的主要问题是如何减小传动系统的容量。常见的恒功率负载有___。
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无论采用的交一直一交变频器是电压型还是电流型，控制部分在结构上均由___三部分组成。
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