黄一钫 发表于 2006-10-29 00:02:27

测量变频器输出电压不能使用数字式仪表的原因

<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: left; mso-pagination: widow-orphan" align=left><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">数字电压表中并无电压线圈，而是首先对被量电压进行采样和模</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">/</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">数转换。在测量变频器的输出电压时，将存在两个问题：</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体"><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt 18pt; TEXT-INDENT: -18pt; TEXT-ALIGN: left; mso-pagination: widow-orphan; tab-stops: list 18.0pt" align=left><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-font-kerning: 0pt"><FONT face="Times New Roman">1</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">、</SPAN><SPAN lang=EN-US style="FONT-SIZE: 7pt; mso-fareast-font-family: 'Times New Roman'; mso-font-kerning: 0pt"><FONT face="Times New Roman">&nbsp; </FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">变频器的输出电压是经</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">SPWM</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">调制过的系列脉冲波，电压的平均值是通过改变脉冲间占空比来进行调节的。这一点，数字电压表将无法接受，它所采样的将是系列脉冲的峰值，而这些值是不变的，都等于变频器的直流电压，所以，数字电压表不可能准确地测出</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">SPWM</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">调制后的平均电压。</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt 18pt; TEXT-INDENT: -18pt; TEXT-ALIGN: left; mso-pagination: widow-orphan; tab-stops: list 18.0pt" align=left><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-font-kerning: 0pt"><FONT face="Times New Roman">2</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">、</SPAN><SPAN lang=EN-US style="FONT-SIZE: 7pt; mso-fareast-font-family: 'Times New Roman'; mso-font-kerning: 0pt"><FONT face="Times New Roman">&nbsp; </FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">普通的数字电压表是用来测量工频电压的，所选用的采用元件和模</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">/</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">数转换元件的工作频率是较低的，而</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">SPWM</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">的调制频率为</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">1.5</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">～</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">15kHz</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">，这将导致采样和模</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; mso-font-kerning: 0pt"><FONT face="Times New Roman">/</FONT></SPAN><SPAN style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体">数转换工作的紊乱，所以，就连测得的峰值也往往是不准确的。</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-font-kerning: 0pt; mso-bidi-font-family: 宋体"><o:p></o:p></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US><o:p><FONT face="Times New Roman" size=3>&nbsp;</FONT></o:p></SPAN></P>

wth 发表于 2006-11-12 19:02:04

Re: 测量变频器输出电压不能使用数字式仪表的原因

学习了

wmgg688 发表于 2006-11-15 10:48:54

Re: 测量变频器输出电压不能使用数字式仪表的原因

谢谢了

hexiaofengxia 发表于 2006-11-23 16:57:21

Re: 测量变频器输出电压不能使用数字式仪表的原因

楼主，指针表的读数正确吗？精度是多少？

旷野寂星 发表于 2014-11-17 20:01:32

学习了

DiodioX 发表于 2014-11-17 22:03:51

hexiaofengxia 发表于 2006-11-23 16:57 static/image/common/back.gif
楼主，指针表的读数正确吗？精度是多少？

指针式的电压表测量频率范围：0Hz-10M。可以真正进行有效值测量。
参见：
http://www.baike.com/wiki/%E7%94%B5%E5%8E%8B%E8%A1%A8
电压表-性能特点


赤发鬼李逵 发表于 2015-6-9 15:37:41

变频器输出的是方波
页: [1]
查看完整版本: 测量变频器输出电压不能使用数字式仪表的原因