直流电机的启动：

将静止(zhi)不(bu)动(dong)(dong)(dong)(dong)的(de)(de)电(dian)(dian)(dian)机的(de)(de)电(dian)(dian)(dian)路与电(dian)(dian)(dian)源接(jie)通(tong)，使电(dian)(dian)(dian)机的(de)(de)转(zhuan)(zhuan)动(dong)(dong)(dong)(dong)部(bu)分旋(xuan)(xuan)转(zhuan)(zhuan)起来，最(zui)后达到正常(chang)运转(zhuan)(zhuan)，叫作电(dian)(dian)(dian)机的(de)(de)启(qi)(qi)动(dong)(dong)(dong)(dong)。若(ruo)不(bu)用任何启(qi)(qi)动(dong)(dong)(dong)(dong)设备而是将电(dian)(dian)(dian)机直接(jie)往电(dian)(dian)(dian)源上连接(jie)，这种启(qi)(qi)动(dong)(dong)(dong)(dong)方法叫作直接(jie)启(qi)(qi)动(dong)(dong)(dong)(dong)，其启(qi)(qi)动(dong)(dong)(dong)(dong)电(dian)(dian)(dian)流很大。由于(yu)当电(dian)(dian)(dian)机刚与电(dian)(dian)(dian)源接(jie)通(tong)时(shi)(shi)，因为电(dian)(dian)(dian)枢(shu)还没(mei)有旋(xuan)(xuan)转(zhuan)(zhuan)，因此反(fan)电(dian)(dian)(dian)动(dong)(dong)(dong)(dong)势等于(yu)零，这时(shi)(shi)通(tong)过电(dian)(dian)(dian)枢(shu)的(de)(de)电(dian)(dian)(dian)流（即启(qi)(qi)动(dong)(dong)(dong)(dong)电(dian)(dian)(dian)流）。

因(yin)为电(dian)(dian)(dian)枢(shu)内电(dian)(dian)(dian)阻很(hen)小，外加电(dian)(dian)(dian)压又是额(e)定(ding)(ding)值，所以电(dian)(dian)(dian)机在直接启动(dong)时的电(dian)(dian)(dian)枢(shu)电(dian)(dian)(dian)流将(jiang)比额(e)定(ding)(ding)电(dian)(dian)(dian)流大十几倍(bei)，甚至几百倍(bei)。这(zhei)样大的电(dian)(dian)(dian)流会(hui)使(shi)得换(huan)向(xiang)(xiang)器上产生强烈的火花，可能把(ba)换(huan)向(xiang)(xiang)器烧坏(huai)。所以，启动(dong)时必须在电(dian)(dian)(dian)枢(shu)电(dian)(dian)(dian)路中串联一个启动(dong)变阻器来减小启动(dong)电(dian)(dian)(dian)流。为了获得较大的启动(dong)转矩(ju)而又不(bu)至于使(shi)换(huan)向(xiang)(xiang)器受(shou)到损伤(shang)，一般把(ba)启动(dong)电(dian)(dian)(dian)流限制(zhi)为电(dian)(dian)(dian)枢(shu)额(e)定(ding)(ding)电(dian)(dian)(dian)流的1.5～2.5倍(bei)。

便可计算出(chu)所需启(qi)(qi)(qi)(qi)动电(dian)(dian)(dian)(dian)阻Rq的(de)数值。在(zai)(zai)启(qi)(qi)(qi)(qi)动过(guo)程中，随着电(dian)(dian)(dian)(dian)机转速(su)的(de)增加，电(dian)(dian)(dian)(dian)枢电(dian)(dian)(dian)(dian)流(liu)逐(zhu)渐减(jian)少，启(qi)(qi)(qi)(qi)动电(dian)(dian)(dian)(dian)阻也应慢慢减(jian)小(xiao)。待电(dian)(dian)(dian)(dian)机转速(su)达到额定值时(shi)，启(qi)(qi)(qi)(qi)动电(dian)(dian)(dian)(dian)阻应减(jian)小(xiao)到零。另外(wai)，在(zai)(zai)启(qi)(qi)(qi)(qi)动时(shi)，还应把励磁电(dian)(dian)(dian)(dian)路中的(de)磁场变阻器Rs放在(zai)(zai)电(dian)(dian)(dian)(dian)阻最(zui)小(xiao)的(de)位置，以使(shi)磁通最(zui)大，这样，就可使(shi)电(dian)(dian)(dian)(dian)机产生(sheng)足(zu)够(gou)大的(de)启(qi)(qi)(qi)(qi)动转矩(ju)，并(bing)使(shi)得反(fan)电(dian)(dian)(dian)(dian)动势(shi)增加较快，以缩短启(qi)(qi)(qi)(qi)动过(guo)程。

直流电机的调速：

由并励直(zhi)流电机(ji)的转速(su)公式可(ke)知，电机(ji)的转速(su)包(bao)括以下三种调(diao)节方(fang)法。

1、改变供电(dian)(dian)线路的(de)电(dian)(dian)压(ya)U　这(zhei)种方法的(de)调(diao)速范围很广泛，但(dan)必须具有专用的(de)直流电(dian)(dian)源。采用发(fa)电(dian)(dian)机-电(dian)(dian)机组以(yi)及(ji)可(ke)(ke)控硅(gui)整流电(dian)(dian)路均(jun)能得到可(ke)(ke)调(diao)节的(de)电(dian)(dian)压(ya)。

2、改(gai)变(bian)电枢线路(lu)的电压降　在(zai)电枢电路(lu)中串(chuan)联(lian)一个调速(su)变(bian)阻器(qi)Rq可减小加在(zai)电枢上的电压。如(ru)果把Rq增(zeng)大(da)，则电阻电压降增(zeng)大(da)，转速(su)n下(xia)降。这种方法因(yin)电枢电流较大(da)，使(shi)得调速(su)变(bian)阻器(qi)本身要消耗(hao)大(da)量的功率，因(yin)此不经济。

3、改(gai)变(bian)磁(ci)极磁(ci)通　在励(li)磁(ci)电(dian)(dian)(dian)路中(zhong)串接一个磁(ci)场(chang)(chang)变(bian)阻器(qi)(qi)(qi)可(ke)以调(diao)(diao)(diao)节(jie)电(dian)(dian)(dian)机转速(su)。如果把磁(ci)场(chang)(chang)变(bian)阻器(qi)(qi)(qi)的(de)(de)(de)阻值增加(jia)，则励(li)磁(ci)电(dian)(dian)(dian)流减(jian)(jian)小，变(bian)阻器(qi)(qi)(qi)中(zhong)通过的(de)(de)(de)磁(ci)通也随之(zhi)而减(jian)(jian)小，电(dian)(dian)(dian)机的(de)(de)(de)转速(su)便升(sheng)高。一般励(li)磁(ci)电(dian)(dian)(dian)路中(zhong)的(de)(de)(de)电(dian)(dian)(dian)流很(hen)小，在调(diao)(diao)(diao)速(su)过程中(zhong)磁(ci)场(chang)(chang)变(bian)阻器(qi)(qi)(qi)的(de)(de)(de)能量损(sun)失也较(jiao)小，比较(jiao)经济(ji)，因此这种(zhong)调(diao)(diao)(diao)速(su)方法(fa)在电(dian)(dian)(dian)力拖动中(zhong)应(ying)用甚(shen)广(guang)。

若(ruo)串(chuan)励电(dian)(dian)机也(ye)采用改变(bian)变(bian)阻(zu)器(qi)(qi)中通(tong)过(guo)的(de)磁(ci)通(tong)的(de)方法来调(diao)节(jie)转(zhuan)速(su)，则磁(ci)场变(bian)阻(zu)器(qi)(qi)必(bi)须(xu)和串(chuan)励绕组并联。当把磁(ci)场变(bian)阻(zu)器(qi)(qi)的(de)阻(zu)值减小(xiao)时，通(tong)过(guo)变(bian)阻(zu)器(qi)(qi)的(de)电(dian)(dian)流增大，而通(tong)过(guo)串(chuan)励绕组的(de)电(dian)(dian)流减小(xiao)，其所产(chan)生的(de)磁(ci)通(tong)也(ye)随着(zhe)减少，转(zhuan)速(su)升(sheng)高。

山(shan)东子昂机(ji)(ji)(ji)电(dian)(dian)(dian)(dian)设备有(you)限公司(si)是一(yi)(yi)(yi)家专注(zhu)高低压电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、电(dian)(dian)(dian)(dian)气产品的维修(xiu)、研发、生产、销售和服(fu)(fu)务(wu)为一(yi)(yi)(yi)体的科(ke)技(ji)型企业(ye)。本公司(si)专业(ye)维修(xiu)：西(xi)安西(xi)玛电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、上海电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、中电(dian)(dian)(dian)(dian)电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、兰州电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、湘(xiang)潭电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、佳木斯电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、沈阳电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、江西(xi)东元电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、无锡电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、六安电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、ＡＢＢ电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、西(xi)门子电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)等各大型高低压电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、直流电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、发电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)、防爆电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)及(ji)同步电(dian)(dian)(dian)(dian)机(ji)(ji)(ji)维修(xiu)、维护、保养(yang)及(ji)现场拆检等服(fu)(fu)务(wu)。本公司(si)本着“科(ke)技(ji)求发展”，“以质量求生存(cun)”，的原则(ze)，始终(zhong)(zhong)坚(jian)持“用户第一(yi)(yi)(yi)、质量第一(yi)(yi)(yi)、服(fu)(fu)务(wu)第一(yi)(yi)(yi)、信誉第一(yi)(yi)(yi)”的企业(ye)宗旨，并将这(zhei)一(yi)(yi)(yi)思想(xiang)始终(zhong)(zhong)贯穿在整个企业(ye)运(yun)行过程之中。