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§2.2鼠笼型电动机的起动控制线路鼠笼型异步电动机常用直接起动和降压起动两种方式,另外还有软起动器、变频器起动等方式。一、直接起动控制线路一般小型台钻和砂轮机等都直接用开关起动,如图2-1所示。uvwFUQM3~×××(b)开关闭合后uvwFUQM3~×××(a)开关闭合前图2-1用开关直接启动线路SB1SB2KMKRKMKMuvwFU1Q×××M~FU2KR(a)未通电时的状态图2-2用接触器启动线路SB1SB2KMKRKMKMuvwFU1Q×××M~FU2KR(b)开启\关断过程SB1SB2KMKRKMKMuvwFU1Q×××M~FU2KR(c)电机过载热继电器断开发热过大二、降压起动控制线1.星—三角降压起动控制线路在正常运行时,电动机定子绕组是联成三角形的,起动时把它联接成星形,起动即将完毕时再恢复成三角形。AA/CBC/B/uwvY型接法ACuA/BC/B/wvΔ型接法KM1uvwKM2M3~KM3SB1SB2KM1KM1KM2KTKM3KM2KM3KTKTKM2uvKM1uvwKM2M3~KM3SB1SB2KM1KM1KM2KTKM3KM2KM3KTKTKM2uv图2-9丫—Δ降压起动控制线路1KM1uvwKM2M3~KM3SB1SB2KM1KM1KM2KTKM3KM2KM3KTKTKM2uvSB1SB2KM1KM1KTKM2KM1KTKTKM2uvKM1uvwKM2M3~KM2KM2图2-10丫—Δ降压起动控制线路2SB1SB2KM1KM1KTKM2KM1KTKTKM2uvKM1uvwKM2M3~KM2KM2SB1SB2KM1KM1KTKM2KM1KTKTKM2uvKM1uvwKM2M3~KM2KM2SB1SB2KM1KM1KTKM2KM1KTKTKM2uvKM1uvwKM2M3~KM2KM2SB1SB2KM1KM1KTKM2KM1KTKTKM2uvKM1uvwKM2M3~KM2KM22.定子串电阻降压起动控制线路电动机起动时在三相定子电路中串接电阻,使电动机定子绕组电压降低,起动后再将电阻短路,电动机仍然在正常电压下运行。KRQuvwFUKM1KRM~×××RKM2SB1SB2KM1KTKM1KM2KTuv图2-11是定子串电阻降压起动控制线路KRQuvwFUKM1KRM~×××RKM2SB1SB2KM1KTKM1KM2KTuv图2-11是定子串电阻降压起动控制线路KRQuvwFUKM1KRM~×××RKM2SB1SB2KM1KTKM1KM2KTuv图2-11是定子串电阻降压起动控制线路KRSB1SB2KM1KTKM2KM1KTKM2KM2KM2QuvwFUKM1KRM~×××RKM2图2-12是定子串电阻降压起动控制线路uvSB1SB2KM1KTKM2KM1KTKRKM2KM2KM2QuvwFUKM1KRM~×××RKM2图2-12是定子串电阻降压起动控制线路uvSB1SB2KM1KTKM2KM1KTKRKM2KM2KM2QuvwFUKM1KRM~×××RKM2图2-12是定子串电阻降压起动控制线路uvSB1SB2KM1KTKM2KM1KTKRKM2KM2KM2QuvwFUKM1KRM~×××RKM2图2-12是定子串电阻降压起动控制线路uvSB1SB2KM1KTKM2KM1KTKRKM2KM2KM2QuvwFUKM1KRM~×××RKM2图2-12是定子串电阻降压起动控制线路uv一、电动机正反转线路KM1uvwKM2M~KRSB1SB2KM1SB3KM2KM1KM2KR图2-13异步电动机正反转控制线路vwKM1uvwKM2M~KRSB1SB2KM1SB3KM2KM1KM2KR图2-13异步电动机正反转控制线路vwKM1uvwKM2M~KRSB1SB2KM1SB3KM2KM1KM2KR图2-13异步电动机正反转控制线路vwKM1uvwKM2M~KRSB1SB2KM1SB3KM2KM1KM2KR图2-13异步电动机正反转控制线路vw上述路图中如果按了SB2又按了SB3,就会造成短路事故。因此这种线路是不能采用的。KM1uvwKM2M~KRSB1SB2KM1SB3KM2KM1KM2KR图2-13异步电动机正反转控制线路vwKM1uvwKM2M~KRSB1SB2KM1SB3KM2KM1KM2KR图2-13异步电动机正反转控制线路vw§2.3电动机正反转控制线路SB1SB2KM1SB3KM2KM1KM2KRKM2KM1KM1uvwKM2M~KR图2-14异步电动机正反转控制线路uvSB1SB2KM1SB3KM2KM1KM2KRKM2KM1KM1uvwKM2M~KR图2-14异步电动机正反转控制线路uvSB1SB2KM1SB3KM2KM1KM2KRKM2KM1KM1uvwKM2M~KR图2-14异步电动机正反转控制线路uvSB1SB2KM1SB3KM2KM1KM2KRKM2KM1KM1uvwKM2M~KR图2-14异步电动机正反转控制线路uv上述接触器KM1、KM2辅助触点这种互相制约关系称为“联锁”或“互锁”。SB1SB2KM1SB3KM2KM1KM2KRKM2KM1KM1uvwKM2M~KR图2-14异步电动机正反转控制线路uvKM1uvwKM2M~KR图2-15异步电动机正反转控制线路SB1SB2KM1KM2KM1KM2KRKM1KM2SB3KM1uvwKM2M~KR图2-15异步电动机正反转控制线路SB1SB2KM1KM2KM1KM2KRKM1KM2SB3KM1uvwKM2M~KR图2-15异步电动机正反转控制线路SB1SB2KM1KM2KM1KM2KRKM1KM2SB3KM1uvwKM2M~KR图2-15异步电动机正反转控制线路SB1SB2KM1KM2KM1KM2KRKM1KM2SB3图2-15异步电动机正反转控制线路KM1uvwKM2M~KRSB1SB2KM1KM2KM1KM2KRKM1KM2SB3只用按钮进行联锁是不可靠的。由于在负载短路或大电流的长期作用时,接触器的主触点可能被“烧焊“在一起,或者接触器的机构失灵,使衔铁卡住总是在吸合状态,不能断开主触点,这时如果另一接触器动作,就会造成电源短路事故。二、正反转自动循环线路ST4ST2ST1ST3工作台M前进后退KM1uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2KR图2-16行程开关控制的正反转线路ST4ST2ST1ST3工作台M前进后退KM1uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2KR图2-16行程开关控制的正反转线路ST4ST2ST1ST3工作台M前进后退KM1uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2KR图2-16行程开关控制的正反转线路ST4ST2ST1ST3工作台M前进后退KM1uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2KR图2-16行程开关控制的正反转线路ST4ST2ST1ST3前进后退KM1uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2KR工作台M图2-16行程开关控制的正反转线路KRST4ST2ST1ST3前进后退KM1uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2工作台M图2-16行程开关控制的正反转线路KM1ST4ST2ST1ST3工作台M前进后退uvwKM2M~KRST2SB1SB2KM1SB3KM2SB3ST4KM2KM1SB2ST1ST3KM1KM2KR图2-16行程开关控制的正反转线路ST3、ST4行程开关起限位保护作用。§2.4电动机制动控制线路制动停车的方式有机械制动和电气制动两大类。机床中经常应用的电气制动有:能耗制动和反接制动。一、能耗制动控制线路能耗制动是在三相异步电动机要停车时切除三相电源的同时,把定子绕组接通直流电源,在转速为零时再切除直流电源。这种制动方法实质上是把转子原来储存的机械能,转变成电能,又消耗在转子的制动上,所以称做能耗制动。SB1SB2KM1KM2KM1KM1KM2KRKM2KTKTuvwFUKRKM1KM2uvKM23M3~图2-18能耗制动控制线路RPSB1SB2KM1KM2KM1KM1KM2KRKM2KTKTuvwFUKRKM1KM2uvKM23M3~图2-18能耗制动控制线路RPSB1SB2KM1KM2KM1KM1KM2KRKM2KTKTuvwFUKRKM1KM2uvKM23M3~图2-18能耗制动控制线路RPSB1SB2KM1KM2KM1KM1KM2KRKM2KTKTuvwFUKRKM1KM2uvKM23M3~图2-18能耗制动控制线路RPSB1SB2KM1KM2KM1KM1KM2KRKM2KTKTuvwFUKRKM1KM2uvKM23M3~图2-18能耗制动控制线路RPSB1SB2KM1KM2KM1KM1KM2KRKM2KTKTuvwFUKRKM1KM2uvKM23M3~图2-18能耗制动控制线路RP制动作用的强弱与通入直流电流的大小和电动机转速有关,在同样的转速下电流越大制动作用越强。一般取直流电流为电动机空载电流的3-4倍,过大会使定子过热。二、反接制动控制线路反接制动实质上是改变异步电动机定子绕组中的三相电源相序产生与转子转动方向相反的转矩,因而起制动作用。反接制动过程为:当想要停车时,首先将三相电源切换,然后当电动机转速接近零时,再将三相电源切除。uvwKM1KM2M3~KR3RBVSB1SB2KM1KM2KM1KM1KM2KRBV图2-19反接制动控制线路KRuvwKM1KM2M3~KR3RBVSB1SB2KM1KM2KM1KM1KM2BV图2-19反接制动控制线路uvwKM1KM2M3~KR3RBVSB1SB2KM1KM2KM1KM1KM2KRBV图2-19反接制动控制线路uvwKM1KM2M3~KR3RBVSB1SB2KM1KM2KM1KM1KM2KRBV图2-19反接制动控制线路uvwKM1KM2M3~KR3RBVSB1SB2KM1KM2KM1KM1KM2KRBV图2-19反接制动控制线路上图的控制方式存在调整不便的问题。采用下图可以改正此问题。KM1uvwKM2M3~KR3RBVKRSB1SB2KM1KM2KM1KM2KM2BVKM1图2-20反接制动控制线路KM1uvwKM2M3~KR3RBVSB1SB2KM1KM2KM1KM2KM2BVKM1图2-20反接制动控制线路KRKM1uvwKM2M3~KR3RBVSB1SB2KM1KM2KM1KM2KM2BVKM1图2-20反接制动控制线路KRKM1uvwKM2M3~KR3RBVSB1SB2KM1KM2KM1KM2KM2BVKM1图2-20反接制动控制线路KRKM1uvwKM2M3~KR3RBVSB1SB2KM1KM2KM1KM2KM2BVKM1图2-20反接制动控制线路反接制动的特点是制动效果显著。但在制动过程中有冲击,对传动部件有害,能量消耗较大。故用于不太经常起制动的设备,如铣床、镗床、中型车床主轴的制动。能耗制动与反接制动相比较,具有制动准确、平稳、能量消耗小等优点。但制动力较弱,特别是在低速时尤为突出。另外它还需要直流电源。故适用于要求制动准确、平稳的场合,如磨床、龙门刨床等的主轴定位。§2.5双速电动机高低速控制线路双速电动机是由改变定子绕组的磁极对数来改变其转速的。在车床、铣床、镗床等中应用较多。1.双速电机的接线原理KMlKMHuWvD4D5D2D3D1D6KMHKMH图2-21双速电动机接线原理图KMlKMHuWvD4D5D2D3D1D6KMHKMH电动机低速运行电动机低速运行时出线端D1、D2、D3接电源;D4、D5、D6端悬空,则绕组为三角形接法,每相绕组中两个线圈串联,成四个极。KMl
本文标题:电气控制2
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