单词复习：Diesel/gasolineenginessynchronous/asynchronousangularvelocitystripslider-crank/campneumaticLesson12MachineToolMotor机床电机Paragraph1Paragraph2:TheBasicMotorsdelivertorquebyshiftingthemagneticfieldswithinthemotor,sotherotorisconstantlydrawnaround.Paragraph3:Withalternatingcurrent(AC)motors,thecurrentitselfswitchesinpolarityfrompositivetonegative.SendingACtothestatorcoilscreatesfieldsthatdrawrotoraround.交流电机中，电流会自动从正极变到负极。将交流电供给定子线圈就会产生磁场使转子旋转起来。Paragraph4:Paragraph5ALittleHistoryButallthisextrahardwareiscostlyandneedsmaintaince.Inthelastdecade,asspeedrequirementshaverisentheinaccuracycausedbyvibration,whichwasnotaproblematlowerspeed,madethecomplexmechanicaltransmissionunacceptableforsomeapplications.Machinetoolbuildersstillusemechanicaltransmissionformanyapplicationsbutbecauseofmoreversatilemotorspeedcontrol,three-speedtransmissionsaremorecommon.在许多应用中，机床制造商仍然在使用机械传动，因为有许多的多用途电机可以调速，所以，以主轴、滑块、附属装置的三种速度运行的传动仍在广泛应用。Fortoday’soperation,consideraspindlespeedfor3600rpmaslowwithhighspeedgenerally10,000rpmandgreater.Somespindles,suchassmall-diametergrindingquills（磨床主轴）,operateat200,000rpm.在如今，人们会认为转速3600转/分钟是低速，高速一般为10000转/分，甚至更高。Atthesametime,motordesignandcontroltechnologyhaveprogresseddramatically.Nowthankstocomputertechnology,it’spossibletoquicklymodifymotorspeedandtorque.同时，电机的设计和控制技术也取得了巨大的进步。现在，要感谢计算机技术，使快速调整电机速度和转矩成为可能。Paragraph7SpindleMotorsTheACasynchronousinductionspindlemotorisalsocalledasquirellcagemotor.Alternatingcurrent-fluctuatingfrompositivetonegativeinasinewave-issenttothreestatorwindingscausingarotatingmagneticfield.异步交流感应主轴电机也叫鼠笼式电机。按正弦波从正到付波动的交变电流传到定子绕组，产生了旋转磁场。Atthesametime,currentinducedintotherotorsetsupanotherfield.Forcessetupbythesetwofieldscauserotorrotation.Tostop,acontrolreversescurrentflow.同时，转子中的感应电流也生成了另一个磁场。这两种磁场形成的力使转子旋转。控制电流反向流动可实现停车。Paragraph9Paragraph10Insometoolchangers（换刀装置）,spindlepositioncontrolisimportantfortoolholder（刀架）orientation.It’snecessarytoknowwherethetoolisforautomatictoolchangerstofunctionp