【单选题】【消耗次数：1】
以下可对异步电机进行调速的方法是（）
①
改变电压的大小
②
改变电动机的供电频率
③
改变电压的相位
④
改变电动机转子绕组匝数
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相关题目
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要改变电容分相式单相异步电动机的转向，应________。
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调换电机的二根进线
②
调换工作绕组的始末端二根进线
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同时调换工作绕组、起动绕组的始末端二根进线
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起动时将电机的转子反向拨动一下
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能耗制动
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机械制动
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回馈制动
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