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<section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(171, 25, 66);"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">一)搞懂变频负载类型</strong></span></section><p><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">变频器的正确选择对于控制系统的正常运行是非常关键的。选择变频器时必须要充分了解变频器所驱动的负载特性。人们在实践中常将生产机械分为三种类型: </span><a class="wx_search_keyword" style="margin: 0px; padding: 0px; outline: 0px; color: var(--weui-LINK); -webkit-tap-highlight-color: rgba(0, 0, 0, 0); cursor: pointer; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">恒转矩负载</a><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">、恒功率负载和风机 、水泵负载。</span></span></section><section><img class="rich_pages wxw-img" src="https://mmbiz.qpic.cn/mmbiz_jpg/ibbYNjL8QYGc3xJZiaTCD5Kb6QSf4m2hdUTtD4aCnicFq2SljsROeoibyV2DMZSREVlJf96U2M3ibibKwem1SXxa6jPA/640?wx_fmt=jpeg&wxfrom=13&tp=wxpic" alt="图片" style="margin: 0px; padding: 0px; outline: 0px; vertical-align: bottom; box-sizing: border-box !important; overflow-wrap: break-word !important; height: auto !important; width: 578px !important; visibility: visible !important;"/></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; background-color: rgb(255, 172, 213); font-size: 15px; letter-spacing: normal;">(01)恒转矩负载</span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">负载转矩TL与转速 n无关,任何转速下TL总保持恒定或基本恒定。例如传送带、搅拌机,挤压机等摩擦类负载以及吊车、提升机等位能负载都属于恒转矩负载。变频器拖动恒转矩性质的负载时,低速下的转矩要足够大,并且有足够的过载能力。如果需要在低速下稳速运行,应该考虑标准</span><a class="wx_search_keyword" style="margin: 0px; padding: 0px; outline: 0px; color: var(--weui-LINK); -webkit-tap-highlight-color: rgba(0, 0, 0, 0); cursor: pointer; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">异步电动机</a><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">的散热能力,避免电动机的温升过高。</span></span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; background-color: rgb(255, 172, 213); font-size: 15px; letter-spacing: normal;">(02)恒功率负载</span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">机床主轴和轧机、造纸机、塑料薄膜生产线中的</span><a class="wx_search_keyword" style="margin: 0px; padding: 0px; outline: 0px; color: var(--weui-LINK); -webkit-tap-highlight-color: rgba(0, 0, 0, 0); cursor: pointer; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">卷取机</a><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">、开卷机等要求的转矩,大体与转速成反比,这就是所谓的恒功率负载。负载的恒功率性质应该是就一定的速度变化范围而言的。当速度很低时,受机械强度的限制,TL 不可能无限增大,在低速下转变为恒转矩性质。如果电动机的恒转矩和恒功率 调速的范围与负载的恒转矩和恒功率范围相一 致时,即所谓“ 匹配” 的情况下, 电动机的容量和变频器的容量均最小。</span></span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; background-color: rgb(255, 172, 213); font-size: 15px; letter-spacing: normal;">(03)风机、泵类负载</span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">在各种风机、水泵、油泵中,随叶轮的转动,空气或液体在一定的速度范围内所产生的阻力大致 与速度n 的 2 次方成正比。随着转速的减小,转矩按转速的2 次方减小。这种负载所需的功率与速度的3 次方成正比。当所需风量、流量减小时,利用变频器通过调速的方式来调节风量、流量,可以大幅度地节约电能。由于高速时所需功率随转速增长过快,与速度的三次方成正比 ,所以通常不应使风机、泵类负载超工频运行。</span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(171, 25, 66);"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">(二)熟悉变频选型原则</strong></span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(51, 51, 51);">(01)结合项目的整体框架,从工艺特点和电气控制入手,负载类型、使用环境、通讯构架和接口类型都必须考虑,比如是串口、DP还是PN通讯接口。</span></span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(02)根据负载特性选择变频器,如负载为恒转矩负载可选择西门子G120变频器,如负载为风机、泵类负载可选择西门子G120XA变频器。</span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">(03)选择变频器时应以实际电机电流值作为变频器选择的依据,电机的额定功率只能作为参考。另外应充分考虑变频器的输出含有高次谐波,会造成电动机的</span><a class="wx_search_keyword" style="margin: 0px; padding: 0px; outline: 0px; color: var(--weui-LINK); -webkit-tap-highlight-color: rgba(0, 0, 0, 0); cursor: pointer; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">功率因数</a><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">和效率都会变坏。因此,用变频器给电动机供电与用工频电网供电相比较,电动机的电流增加10%而温升增加约20%。所以在选择电动机和变频器时,应考虑到这种情况,适当留有裕量,以防止温升过高,影响电动机的使用寿命。</span></span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">(04)变频器若要长电缆运行时,此时应该采取措施抑制长电缆对地耦合电容的影响,避免变频器出力不够,所以变频器应放大一档选择或在变频器的输出端安装输出</span><a class="wx_search_keyword" style="margin: 0px; padding: 0px; outline: 0px; color: var(--weui-LINK); -webkit-tap-highlight-color: rgba(0, 0, 0, 0); cursor: pointer; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">电抗器</a><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">。</span></span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(05)对于一些特殊的应用场合,如高环境温度、高开关频率(尤其是在楼宇自控等对噪音限制较高的应用场所使用时需注意)、高海拔高度等,此时会引起变频器的降容,变频器需放大一档选择。</span></section></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(06)当变频器用于控制并联的几台电机时,一定要考虑变频器到电动机的电缆的长度总和在变频器的容许范围内。如果超过规定值,要放大一档或两档来选择变频器。另外在此种情况下,变频器的控制方式只能为V/F控制方式,并且变频器无法保护电动机的过流、过载保护,此时需在每台电动机上加熔断器来实现保护。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(07)对于一些特殊的应用场合,如高环境温度、高开关频率、高海拔高度等,此时会引起变频器的降容,变频器需放大一档选择。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(08)使用变频器控制高速电机时,由于高速电动机的电抗小,高次谐波亦增加输出电流值。因此,选择用于高速电动机的变频器时,应比普通电动机的变频器稍大一些。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(09)变频器用于变极电动机时,应充分注意选择变频器的容量,使其最大额定电流在变频器的额定输出电流以下。另外,在运行中进行极数转换时,应先停止电动机工作,否则会造成电动机空转,恶劣时会造成变频器损坏。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(10)驱动防爆电动机时,变频器没有防爆构造,应将变频器设置在危险场所之外。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(11)使用变频器驱动齿轮减速电动机时,使用范围受到齿轮转动部分润滑方式的制约。润滑油润滑时,在低速范围内没有限制;在超过额定转速以上的高速范围内,有可能发生润滑油用光的危险。因此,不要超过最高转速容许值。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(12)变频器驱动绕线转子异步电动机时,大多是利用已有的电动机。绕线电动机与普通的鼠笼电动机相比,绕线电动机绕组的阻抗小。因此,容易发生由于纹波电流而引起的过电流跳闸现象,所以应选择比通常容量稍大的变频器。一般绕线电动机多用于飞轮力矩GD2较大的场合,在设定加减速时间时应多注意。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(13)变频器驱动同步电动机时,与工频电源相比,降低输出容量10%~20%,变频器的连续输出电流要大于同步电动机额定电流与同步牵入电流的标幺值的乘积。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(14)对于压缩机、振动机等转矩波动大的负载和油压泵等有峰值负载情况下,如果按照电动机的额定电流或功率值选择变频器的话,有可能发生因峰值电流使过电流保护动作现象。因此,应了解工频运行情况,选择比其最大电流更大的额定输出电流的变频器。变频器驱动潜水泵电动机时,因为潜水泵电动机的额定电流比通常电动机的额定电流大,所以选择变频器时,其额定电流要大于潜水泵电动机的额定电流。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(15)当变频器控制罗茨风机时,由于其起动电流很大,所以选择变频器时一定要注意变频器的容量是否足够大。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(16)选择变频器时,一定要注意其防护等级是否与现场的情况相匹配。否则现场的灰尘、水汽会影响变频器的长久运行。</span></p><p style="margin-top: 0px; margin-bottom: 16px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-family: system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; background-color: rgb(255, 255, 255); line-height: 2em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(17)单相电动机不适用变频器驱动。</span></p><p><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px; letter-spacing: normal;">(18)电机负载非常轻时,即使电机负载电流在变频器额定电流之内,亦不能使用比电机容量小很多的变频器。这是因为电机的电抗随电机的容量而不同,即使电机负载相同,电机容量越大其脉动电流值也越大,因而有可能超过变频器的电流容许值。</span></section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; letter-spacing: normal;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 15px;">(19)如果变频器的供电电源是自备电源,最好加上进线电抗器。</span></span></section></p><p><br/></p> |