电大机械本科机电控制与可编程控制器技术分析复习题小抄参考

1、三、读图分析： 一、图为单向起动反接制动控制线路。此电路采用速度继电器来检测电动机转速的变化。在1203000rpm。范围内速度继电器触头动作，当转速低于100 rpm时；其触头复位、图中km1为单向旋转接触器，km2为反接制动接触器，ks为速度继电器，r为反接电阻、试分析该线路的工作过程答：起动时按下sb2，km1通电并自锁，电动机运转，当转速上升到120rpm以上时，速度继电器ks的常开触头闭合，为反接制动做准备当按下停止复合按钮时，sb1常闭触点先断开，km1断电，电动机脱离电源，靠惯性继续高速旋转，ks常开触头仍闭合当sb1常开闭合后，km2通电井自锁，电动机串接电阻接反相序电源电动机

2、进人反接制动状态，转速迅速下降当电动机转速降到低于100rpm时，速度继电器ks的常开触点复位，km 2断电，反接制动结束电动机脱离电源后自然停车。二、如图所示为y一降压起动控制线路，试分析其工作过程，并说明kmy与km的常闭触点的作用。答：kmy与km的常闭触点是保证接触器kmy与km不会同时通电，以防电源短路（3分）km的常闭触点同时也使时间继电器kt断电（起动后不需要kt得电）（3分）。三、下图所示为异步电动机的能耗制动控制线路，试分析该电路的工作过程答：按下启动按钮sb2-接触器km1通电并自锁，主电路中的常开触点闭合，电动机启动。答案（4分）四、 下图所示为三相鼠箱式异步电动机串电阻

3、起动控制线路，说明电路中fu和fr的作用，并分析该电路的起动过程km2的作用？ 答：fu起短路保护作用（4分）fr起过载保护作用（4分）。该电路的起动过程如下按下起动按钮sb2，接触器km1得电并自锁，主电路中km1的常开主触点闭合，电动机串电阻降压起动，同时时间继电器kt也得电。当kt的延时时间到了以后，其通电延时闭合的触点闭合，使接触器km2得电并自锁，km2的常闭触点断开，km1和kt均断电，主电路中km1的常开主触点断开，km2的常开主触点闭合，电阻r被短路掉，电动机常压运行（6分）五、下图所示为两台电动机的电气控制线路，a）为主电路，b）为控制电路。试说明fu和fr的作用分析此电住的

4、工作原通（过程）并说明出连锁功能是知何实现的答： fu是起短路保护的熔断器（5分）fr是起过载保护作用的热继电器（5分）。电路的工作过程如下：合上刀开关q按下起动按钮sb3，接触器km1的线圈得电并自锁，主电路中其常开触点闭合，电动机m1起动。按下起动按钮sb2，接触器km2的线圈得电并自锁，主电路中其常开触点闭合，电动机m2起动。sb2是电动机m2的停止按钮，按下它，接触器km2的线圈断电，电动机m2停止。sb1是总停止按钮，按下它，电动机m1和电动机m2均停止，此电路中，将接触器km1的一个常开触点串联在接触器km2的线圈电路中，保证只有当电动机m1起动后，电动机m2才能起动，即实现了联锁

5、功能。（l0分）六、下图为两个电动机控制线路。试分析该线路的工作过程。km2m13m23km3fr1fr2km1qu v wfu1fu2sb2km3km1km3sb1km2km2sb4km2km1km1km2sb3km3km3km1fr1fr2答：m1电动机能够正、反转；m2电动机单方向运转。两个电动机互锁。电动机都有熔断器和热继电器保护。读图分析(共20分) 下图所示为机床工作台自动往复行程控制的电路，行程开关st1、st2分别装在机床床身的两侧需要返回的位置，挡铁装在工作台上。试分析该电路的工作过程，并说明行程开关st3、st4以及接触器km，和km2的常闭触点的作用四图(5)所示为三相鼠

6、笼式异步电动机串电阻起动控制线路，说明 、 电路中fu和fr的作用，并分析该电路的起动过程。(20分)按下起动按钮sb2接触器km1得电，电源通过电阻r加到电动机定子绕组上，降压起动(7分)。由时间继电器控制其降压起动的时间，时间继电器延时时间一到，其常开触点闭合，使接触器km1的线圈得电，同时接触器km1和kt的线圈失电，电阻r从电网中切除，电动机在正常电压下运行(7分)。fu是熔断器，起短路保护作用；fr是热继电器，起长期过载保护作用。(6分)winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final w

7、in over england, has been passed fit after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in thei

8、r first pool match against england on the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most

9、 interest in the tournament so far.the kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line th

10、is weekend, said williams.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomo

11、rrow and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president

12、 of european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: mi

13、ssion aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, wil

14、l move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stra

15、tosphere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they g

16、ot caught cold in the final and they will not make the same mistake against the kiwis in manchester.five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by englands josh charnley in the opening game of the tournament.tha

17、t could be classed as a weakness, a team under-cooked - but i have been impressed by the kangaroos focus in their games since then.they have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick

18、-chase. theyve been great at all the unglamorous stuff that often goes unnoticed in the stands but not by your team-mates.it is as though their entire tournament has been preparation for the final.in johnathan thurston, cooper cronk, cameron smith and either billy slater or greg inglis at full-back they have a spine that is unmatched in rugby league. they have played in so many high-pressure games - a priceless as