千万不要随便测试变频器输出电压（2）

<p><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; color: rgb(255, 255, 255); font-family: system-ui, -apple-system, BlinkMacSystemFont, &quot;Helvetica Neue&quot;, &quot;PingFang SC&quot;, &quot;Hiragino Sans GB&quot;, &quot;Microsoft YaHei UI&quot;, &quot;Microsoft YaHei&quot;, Arial, sans-serif; font-size: 15px; letter-spacing: 0.5px; white-space: normal; background-color: rgb(105, 188, 145); visibility: visible; box-sizing: border-box !important; overflow-wrap: break-word !important;">最后总结：</strong></p><p><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; color: rgb(255, 255, 255); font-family: system-ui, -apple-system, BlinkMacSystemFont, &quot;Helvetica Neue&quot;, &quot;PingFang SC&quot;, &quot;Hiragino Sans GB&quot;, &quot;Microsoft YaHei UI&quot;, &quot;Microsoft YaHei&quot;, Arial, sans-serif; font-size: 15px; letter-spacing: 0.5px; white-space: normal; background-color: rgb(105, 188, 145); visibility: visible; box-sizing: border-box !important; overflow-wrap: break-word !important;"></strong></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; caret-color: red; color: rgb(12, 12, 12); letter-spacing: 0.5px; visibility: visible;">1、通常我们说的变频器输出380V、50Hz，是指其基波（正弦波）为380V、50Hz。变频器实际输出波形为PWM波，除了基波外，还包含载波信号。载波信号频率要比基波高得多，且是方波信号，包含大量的高次谐波。</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; color: rgb(12, 12, 12); font-size: 15px; letter-spacing: 0.5px;">2、普通万用表一般只能测量45~66Hz或45~440Hz的交流正弦波。部分真有效值万用表的测量频率范围要宽得多，许多人认为可以用于变频测量、测试。其实不然，因为这种表测量结果把基波和载波都包含进去了。比如上述变频器，380V输出时，测量结果一般在400V以上。</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(12, 12, 12); font-size: 15px; letter-spacing: 0.5px;">3、用于变频测试的仪表应具备在各种PWM波形中分解出其基波的能力，严格测量需采用数字信号处理的方式，也就是高速采样得到样本序列，再对样本序列进行离散傅里叶变换，得到基波有幅值、相位及各次谐波的幅值和相位。</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(12, 12, 12); font-size: 15px; letter-spacing: 0.5px;">4、也有一种思路认为校准平均值可以替代变频器输出PWM信号中的基波成分的有效值。准平均值（MEAN）在理论上等于正弦波的真有效值，等于正弦调制PWM波形的基波有效值，且实现简单；因此，MEAN在许多仪器仪表中用于替代正谐波的有效值（RMS）或PWM的基波有效值（H01）的测量。但是，近年来，变频调速技术日新月异，非正弦调制PWM的应用越来越多，而且，变频器用户通常并不了解自己的变频器采用何种调制模式，MEAN值在PWM测量中局限性越来越大。</span></section></p><p><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; color: rgb(255, 255, 255); font-family: system-ui, -apple-system, BlinkMacSystemFont, &quot;Helvetica Neue&quot;, &quot;PingFang SC&quot;, &quot;Hiragino Sans GB&quot;, &quot;Microsoft YaHei UI&quot;, &quot;Microsoft YaHei&quot;, Arial, sans-serif; font-size: 15px; letter-spacing: 0.5px; white-space: normal; background-color: rgb(105, 188, 145); visibility: visible; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></strong><br/></p>