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PART1U1T1、Inadditiontothevariouspowertransformers,twospecial-purposetransformersareusedwithelectricmachineryandpowersystems.Thefirstofthesespecialtransformersisadevicespeciallydesignedtosampleahighvoltageandproducealowsecondaryvoltagedirectlyproportionaltoit.Suchatransformerisapotentialtransformer.Apowertransformeralsoproducesasecondaryvoltagedirectlyproportionaltothatthepotentialtransformerisdesignedtohandleonlyaverysmallcurrent.Thesecondtypeofspecialtransformerisadevicedesignedtoprovideasecondarycurrentmuchsmallerthanbutdirectlyproportionaltoitsprimarycurrent.Thisdeviceiscalledacurrenttransformer.除了各种电源变压器、两个专用变压器使用电动机械和电力系统。第一个特殊变压器是一个高电压设备专门设计的样品和生产较低的二次电压成正比。这样一个变压器电压互感器。电力变压器也产生二次电压成正比的电压互感器的设计目的是处理只有一个很小的电流。第二种类型的特殊变压器是一个装置,旨在提供一个次级电流小得多,但它的主要电流直接成比例。这种装置称为电流互感器。U1T2、Inelectronicpowersuppliesthereisoftenaneedtoisolatetheoutputfromtheinputandreducetheweightandcostoftheunit.Inotherapplications,suchasinaircraft,thereisastrongincentivetominimizeweight.Theseobjectivesarebestachievedbyusingarelativelyhighfrequencytransformer.Thus,inaircraftthefrequencyoftransformersistypically400Hz,whileinelectronicpowersuppliesthefrequencyoftransformersmayrangefrom5kHzto50kHz.在电子电源通常需要隔离的输出输入,减少单位的重量和成本。在其他应用程序,如飞机,有强烈的动机来减少体重。这些目标是最好通过使用一个相对高频变压器。因此,在飞机变压器通常是400赫兹的频率,而在电子电源变压器可能范围从5khz的频率50千赫U2T1、Ingeneral,theoutstandingadvantageofDCmachinesliesintheirflexibilityandversatility.BeforethewidespreadedavailabilityofACmotordrives,DCmachineswereessentiallytheonlychoiceavailableformanyapplicationsrequiringahighdegreeofcontrol.TheirprincipaldisadvantagesstemfromthecomplexityassociatedcomplexityincreasethecostovercompetingACmachines,italsoincreasestheneedformaintenanceandreducesthepotentialreliabilityofthesemachines.一般来说,直流机的突出优势在于他们的灵活性和通用性。交流电动机驱动的广泛可用性之前,直流机基本上是唯一可用的选择对于许多应用程序要求高度的控制。主要缺点源于复杂关联的复杂性增加了成本在竞争交流的机器,它也增加了对维护的需要,减少了潜在的这些机器的可靠性。U2T2、Therearethreebasictypeofrotatingmachines:synchronous,induction,andDCmachines.Inallofthemthebasicprinciplesareessentiallythesame.Voltagesaregeneratedbytherelativemotionofamagneticfieldwithrespecttoawinding,andtorquesareproducedbytheinteractionofthemagneticfieldsofthestatorandrotorwindings.有三种基本类型的旋转机器:同步,感应,直流机器。在所有这些基本原则基本上是相同的。电压的相对运动产生的磁场对绕组,和扭矩的交互作用是由定子和转子绕组的磁场。U3T1、Synchronousmachinescanbeclassifiedascylindrical-rotororsalient-polemachines.Thecylindrical-rotorconstructionisusedinhigh-speedsteam-turbine-drivengenerators.Thearmaturewindingsconsistoflaminatedconductorsplacedinthestatorslots.TherotorcarriestheDCfieldwinding.Mostofturbinegeneratorsbeingbuiltatpresentfor60Hzserviceare2-pole3600revolutionsperminutemachines.Becauseoftheeconomiesofhigh-speedhigh-temperaturehigh-pressuresteamturbines,muchstudyandsomerealpioneeringworkhavebeendevotedtoimprovementsinmaterialsanddesignofbothgeneratorsandturbines同步机可分为圆柱形转子或凸极机。圆柱形转子建设用于高速steam-turbine-driven发电机。电枢绕组由叠层导体放置在定子槽。转子直流磁场绕组。目前大部分涡轮发电机建60赫兹服务2-pole每分钟3600转的机器。因为经济的高速高温高压蒸汽涡轮机,多学习和一些真正的开创性工作一直在致力于改进材料和设计的发电机和发电机U3T2、Rotatingelectricmachinestakemanyformsandareknownbymanynames:DC,synchronous,permanent-magnet,induction,etc.Althoughthesemachinesappeartobequitedissimilarandrequireavarietyofanalyticaltechniques,thephysicalprinciplesgoverningtheirbehaviorarequitesimilar,andinfactthesemachinescanoftenbeexplainedfromthesamephysicalpicture.Aninductionmachine,inspiteofmanyfundamentaldifferences,worksonexactlythesameprinciple;onecanidentifyfluxdistributionsassociatedwiththerotorandstator,whichrotateinsynchronismandwhichareseparatedbysometorque-producingangulardisplacement.旋转电机采取多种形式和已知许多名字:直流、同步、永磁、感应,等等。虽然这些机器似乎是相当不同的,需要各种分析技术,管理他们的行为非常相似的物理原则,事实上这些机器通常可以解释从相同的物理图像。感应式电机,尽管许多根本性的差异,同样的原理工作;一个可以识别通量分布与转子和定子,在同步旋转,由一些torque-producing角位移U4T1、ThesignificanceofVRMsinengineeringapplicationsstemsfromtheirlowcost,reliability,adncontrollability.Becausetheirtorquedependsonlyonthesquareoffappliedstatorcurrentsandnotontheirdirection,thesemachinescanbeoperatedfromunidirectionaldrivesystems,reducingthecostofthepowerelectronics.However,itisonlyrecently,withtheadventoflow-cost,flexiblepowerelectroniccircuitryandmicroprocessor-basedcontrolsystems,VRMshavebeguntoseewidespreadapplicationinsystemsrangingfromtractiondrivestohigh-torque,precisioncontrolsystemsforroboticsapplications.VRMs在工程应用的意义源于他们的低成本、可靠性、可控性。因为他们的转矩只取决于广场采用定子电流,而不是他们的方向,这些机器可以从单向操作驱动系统,减少电力电子的成本。然而,直到最近,随着低成本、灵活的电力电子电路和基于微处理器控制系统,VRMs已经开始看到广泛应用系统从牵引驱动高扭矩,为机器人精度控制系统应用程序U4T2、Thehybridsteppingmotorcombinescharacteristicsofthevariable-reluctanceandpermanent-magnetsteppingmotors.Thehybridsteppingmotorcanachievesmallstepsizeseasilyandwithasimplemagnetstructurewhileapurelypermanent-magnetmotorwouldrequireamultipolepermanentmagnet.Inaddition,thehybridsteppingmotorwilltendtomaintainitspositionwhenthestatorexcitationisremoved,asdoesthepermanent-magnetdesign.混合式步进电机结合可变磁阻和永磁步进电动机的特性。混合式步进电机可以实现小步大小很容易和磁铁结构简单而纯粹的永磁电动机需要多极永磁。此外,混合步进电机将倾向于保持其位置移除定子励磁时,永磁设计一样。U5T1、Relayisakeycomponentinanypowersystemprotectionscheme.Itisadevicethat,basedoninformationreceivedfromthepowersystem,performsoneormoreswitchingactions.Thein