【判断题】【消耗次数:1】
一般的直流电动机起动时,采用的方法是降低电源电压。
正确
错误
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相关题目
【单选题】 直流电动机采用降低电源电压的方法起动,其目的是: ( )
①  为了使起动过程平稳
②  为了减小起动电流
③  为了减小起动转矩
【判断题】 小容量直流电动机可采用直接起动。
①  正确
②  错误
【单选题】 在直流电动机中,机械特性最硬的一般为( )
①  并励电动机
②  他励电动机
③  串励电动机
【单选题】 改变直流电动机的转向方法有________。?
①  对调接电源的两根线
②  改变电源电压的极性
③  改变主磁通的方向或改变电枢中电流方向
【单选题】 直流电动机调速方法不包含(?? ?)。?
①  电枢回路串电阻
②  励磁回路串电阻
③  变频调速
④  调节电枢电压
【判断题】 起动直流电动机时,励磁回路应与电枢回路同时接入电源。
①  正确
②  错误
【单选题】 并励直流电动机,当电源反接时,转速方向( )。
①  反向
②  不变
③  不确定
【单选题】 直流电动机常用()方法实现反转。
①  改变磁通方向
②  增加电枢电阻
③  改变电枢电流方向
④  以上选项都不对
【单选题】 他励直流电动机( ),不适合频繁起动的大、中型电动机
①  电枢回路串电阻起动
②  降压起动
③  直接起动
【判断题】 直流电动机中包括鼠笼式电动机。
①  正确
②  错误
随机题目
【单选题】 10. ______, he was unable to make much progress.
①  Hard as he tried
②  Though hard as he tried
③  He tried hard
④  Because he tried hard
【单选题】 6. She felt herself ______ by the wind.
①  lift
②  lifting
③  has been lifted
④  lifted
【单选题】 9.She does not_____ that she owes the money, but she just wouldn’t like to return it.
①  argue
②  . dispute
③  think
④  agree
【单选题】 9. By 2008, Beijing ______ its total discharge of pollutants.
①  will reduce
②  will have reduced
③  reduces
④  has reduced
【单选题】 5. The children were seen _______ musical instruments across the street.
①  play
②  to play
③  playing
④  played
【单选题】 8. ______, he was honest.
①  As he was poor
②  Being poor
③  Poor as he was
④  He was poor
【单选题】 12. I’m very sorry to have _______ you with so many questions on such an occasion.
①  interfered
②  offended
③  impressed
④  bothered
【单选题】 7. It is so quiet that you can hear a pin ______.
①  dropping
②  . dropped
③  drop
④  drops
【单选题】 4. The instructor watched the student ____ the test.
①  to take
②  take
③  takes
④  took
【单选题】 20. _____ the sight of the poor and the sick, the government had no way out but to decided to reform..
①  Seeing
②  Confronted with
③  Confronting
④  Looking at